The Basics on Drains, Traps and Vents, DIY

The Basics on Drains, Traps and Vents


different drains,traps,vents found in typical home

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Whenever water comes into a home, it has to have a way to leave after it’s been used. This is where the importance of drains and proper drainage comes into play. Most homes utilize the same basic principles for plumbing and drain systems: A main water line usually comes in around the home’s foundation; from this point, it runs over to a water heater. The water heater generates hot water for the entire house. From the water heater, hot and cold water lines run throughout the house, supplying each of the fixtures with water.

Most people don’t realize how a home drainage system works; they assume that when they release water from the sink or flush a toilet, the water just goes away. Although this is partially true, a little more is involved in the process of removing waste water from the home. Each fixture has its own drain line; each of the drain lines ties into a larger main line, which takes the water out of the house.

People who live in urban and suburban areas and get their water from a municipality usually have their waste water drain into a sewer system. Septic tanks generally need to be pumped out every 10 years or so to prevent backup, which can cause problems with the home’s drainage system.

The most important component of a drain, which most people take for granted, is the trap. They’re called traps because they do just that: trap water inside, preventing sewer gases from coming back into the house.

Several connections are needed when connecting a trap. First is the nut, which connects two pieces together with a threaded fitting. A ferrule forms the seal; the nut simply screws down over the ferrule to form a water tight seal.

Vents are a major component in a home’s drainage system. Venting allows water to pass out of the drains easily. Today, houses are vented through the roof. Roof flashing, made from heavy grade rubber, lead or sheet metal holds the vent pipe in place.

Another thing to consider is pitch. Pitch simply means the angle in which water will flow easily and gradually with the help of gravity. Every drainpipe, whether underground or in a wall, must have some type of pitch and be sloped properly to allow wastewater leaving the home to drain out. To ensure water will drain properly and won’t back up in the line, a good rule of thumb to follow when installing pipe is a drop of 1/4 inch per foot.

How to Unclog a Toilet Trap

Clearing a Clog With a Plunger and a Toilet Auger

A toilet trap, or trapway, is a curving channel inside the base of a toilet that leads from the hole at the bottom of the bowl to the drainpipe. When a toilet backs up and the clog did not occur in the drainpipe, the stoppage usually exists in the trap. You can determine whether a clog is in the toilet’s trap or further down in the drain by checking the sink and/or tub drains. Toilets, bathroom sinks, and tubs almost always drain out into the same main drain pipe, so if the sink or tub is draining without a problem, then the clog most likely lies in the toilet’s trap.

Most toilet clogs can be cleared using a toilet plunger (not a regular cup-shaped plunger). Failing that, that next thing to try is a toilet auger, which is a special type of plumbing drain snake designed for toilets.

Clogs in the Toilet Trap

Anything from tissues to paper towels to hygiene products can cause a toilet trap to clog. These items should never be flushed down the toilet. Disposable wipes, even those labeled as «flushable,» also should never be flushed because they do not break down easily when wet, like toilet paper does. If you have small children, you’re probably familiar with kids’ preoccupation with the toilet. Flushed toys are very common causes of clogs in traps. Even some adults, who might be afraid to touch toilet water, may attempt to flush items accidentally dropped into the toilet rather than fishing them out.

How to Clear a Toilet Trap With a Plunger

Plunging is effective for clearing most paper-related clogs, even tough ones, so it’s the best method to try first. If plunging doesn’t work, you may have a hard object creating the stoppage and should move to a toilet auger. For the best results, use a toilet plunger, also called a flange plunger, rather than a standard sink plunger. A toilet plunger has a bell-shaped cup with an extendable flange that fits into the hole in the toilet bowl to create a good seal.

  1. Make sure there is enough water in the toilet bowl to fill the cup of the plunger and seal around the cup when it is placed over the hole.
  2. Set the plunger into the water of the bowl so the plunger cup is at an angle. This allows the cup to fill with water, which increases the plunging force. Press the cup over the hole to create a seal.
  3. Carefully pump the plunger in and out with an even but vigorous motion while maintaining the cup’s seal over the hole. The plunging action forces water in both directions in the drain, in a sort of push-pull motion, to loosen the clog. Plunge five or six times, then pull up the plunger and see if the clog has cleared.
  4. Repeat the previous step as needed. If you can’t clear the clog after 10 or so attempts, it’s probably time to try an auger.

How to Clear a Toilet Trap With a Toilet Auger

A toilet auger, also called a closet auger, consists of a J-shaped tube and a cable that’s turned by a handle. It works the same way as a drain snake, but the tube allows you to feed the cable into the trap while protecting the toilet bowl from damage. You can buy a toilet auger at hardware stores and home centers for less than $15.

Sewer House Traps Need Proper Caps or Plugs to Function Properly

potemtial Believe it or not a house trap on a sewer line is vitally important in many ways that you would probably never think of. That “thing” you see in the bottom of a pit in your basement can cause an awful lot of aggravation. Open sewer traps can also cause damage if they are not functioning properly, are in poor condition, or are not operated properly.

Sewer Traps: Knowing the proper Caps and Plugs to use

Trap plugs or caps cost around $10.00 or less each. They are made in at least three varieties, and are readily available from any plumbing supply or local hardware store. They are easily installed on a house sewer using basic household tools or can be installed by your plumber.

Whoever takes the time to install a new plug or cap will be paying a small price for preventing potential damage. A tightly closed trap also avoids inconveniences such as rodent or pest infestation. In addition, this minor maintenance can prevent an unhealthy condition from noxious gases entering in your property from your drain line. This is another case where performing minor plumbing maintenance is well worth the effort.

What are the dangers of sewer traps not properly sealed?

  • Will allow noxious gases to escape into the premises from your sewer line.
  • Allow for rodents and insects (but not alligators) to enter into a premises.
  • Can allow raw sewage to enter into a premise if a back up occurs.
  • If the public sewer surcharges, you will get inundated with sewage.

What is the preferred type of cap or plug for a trap?

A cap is used when meant to fit over the outer edge of the sewer trap. In this case the preferred cap is called a jim cap. It has an adjustable metal band around it that makes it extremely water tight. When a plug is needed the recommended plug is called a wing nut test plug. It is also likewise adjustable and extremely water tight. Both of these items are ideal when needed for an existing trap which may be slightly worn or have some corrosion present on the contact points.

Why A Double Vent Trap Is So Important

A double vent trap allows for cleaning of your drain pipe in two directions. A house drain can be easily cleaned either out towards the public sewer or towards the inside house drain. A single vent style unit is not legal for a sanitary NYC house sewer primarily because it is much harder to perform cleaning when required.

Another important factor is that water is held in the bottom of a house trap. This water creates a barrier which prevents any harmful or unpleasant sewer gases from entering into your property.

House sewer traps serve many purposes

Sometimes when a sewer is unused for some time there will be a foul sewer smell in a property because the water in the bottom of the house trap has dried up and evaporated. Simply running some water inside the property will fill the bottom of the house trap back up again and solve the problem.

What Plumbing Material Is Best?

Various materials are used in the manufacture of house drain pipe and fittings. In the case of a trap PVC, service weight cast iron, and extra heavy cast iron can be used legally in NYC in most cases. One exception is that PVC is not legal for commercial properties. Because a trap is prone to be opened and closed repeatedly and have electric snakes placed in them for cleaning it is strongly suggested that extra heavy cast iron be used.

PVC is prone to crack or wear out from cleaning, and service weight cast iron rusts and corrodes much sooner than extra heavy. Pipe and fittings made from extra heavy cast iron pipe can withstand decades of wear and tear without any fear of damage or the need for future repairs – in addition the cost difference is not substantial.

Trap made from PVC fittings

An extra heavy cast iron sewer trap will last longer and be much more durable than pvc , no hub, or service weight cast iron. It is well worth the cost difference in the long run.

It should be noted that double vent PVC traps are not manufactured. They have to be made by putting together different fittings such as a return bend and two tee-wyes. Another point to note is that sewer cleaning machines use sharp and abrasive blades. When inserted into a trap these blades come into direct contact with the walls of the trap. This is another reason PVC is not recommended. PVC can be damaged when contacted directly by sewer cleaning blades in this way.

How To Open A House Trap Properly And Safely

  • Whenever possible make sure the public sewer is not backed up prior to opening a house trap. If a public or NYC sewer is backed up and a house trap is opened is could be disastrous. The public or NYC sewer will then drain out of your house drain and fill your premises with raw sewage. This can potentially cause extensive damage with severe health ramifications.
  • Always open the “street side” plug first. That way if there is a trap stoppage, the back up can flow over the opened plug. It will then flow out to the street when the “house side” plug is opened. If the “house side” plug is opened first and there is a stoppage the backed up waste water will have no means to escape and will fill up your sewer pit or dump on your floor.

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How to Install and Clean a Grease Trap (for Your Home)

Cooking with grease can be messy. If left unchecked, this accumulation of waste can not only turn out to be an expensive process to undo but can also become extremely gross. Even worse, grease can clog sewer lines within the neighborhood and create problems at local water treatment facilities. Therefore, it is a bad idea to pour fats, oils, and grease down the kitchen drain.

To help mitigate against any issues arising from clogged sewer lines you need a grease trap.

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What is a grease trap?

Simply put, a grease trap (also commonly known as a grease convertor, grease recovery device, and grease interceptor) is a plumbing fixture designed to intercept most solids and greases before entering the sewer waste system.

Capacity ranges from 35 liters to 45,000 liters and can be constructed from many different materials, including cast iron, concrete, plastics, and stainless steel. The grease traps can be located in areas such as inside and outside the kitchen, and above and below ground.

Benefits of having a Grease Trap in Your Home

Needless to say, a grease trap is an invaluable addition to any working kitchen. If you’re an avid cook and are constantly flushing grease down your sink, you’re definitely going to want to read about the following benefits: It is not only beneficial to the environment but also financially.

1. Environmentally friendly

Grease traps help keep the environment clean by reducing pollution. When you cook without a grease trap the fats, oils, and grease (FOG) flow into local streams and rivers. FOG can become toxic over time. A grease trap intercepts the FOG before it reaches your sewage system. In addition, the FOG can be converted into rich agricultural mulch that can be used in farms as a fertilizer.

2. Economically Beneficial

Having grease traps installed will greatly reduce the expensive repairs and maintenance that accrue from blocked pipes. As long as a grease trap is properly maintained, you won’t have to worry about having a blocked sewer system. Additionally, maintaining a grease trap is hassle free. They’re quite easy to clean.

Grease Trap Sizing

Grease traps come in a variety of sizes, from individual kitchen models to ones large enough to be fitted in big eateries and restaurants. For residential grease traps, we highly recommend hiring the services of a professional so as to ascertain the right size for your needs.

How does a grease interceptor work?

A grease trap works by cooling warm or hot greasy water. Vegetable oils and animal fats are 10 to 15% less dense than water and are insoluble in water. By allowing the fats, oils, and grease to cool, the different layers of the mixture are able to separate into individual layers for easy separation.

Since the FOG is lighter in density, it is able to float on top, and the water beneath is left to continue flowing down the drain. The floating FOG is then trapped by a grease trap.

Over time, grease and solids build up, and if the accumulation is left unchecked for long, can block the inlet. As such, grease traps need to be pumped/cleaned out on a regular basis.

Below is an illustration of how a grease trap works:

Types of Grease Traps

There are three different types of grease traps; gravity, automatic, and passive hydromechanical (manual). The former two are mainly used for large installations like restaurants or hotels, while the passive hydromechanical grease trap is used in homes.

We’re going to focus on residential grease traps but if you would like more information on commercial grease traps check out this article.

The passive hydromechanical (manual) grease trap is a traditional passive system commonly used in smaller establishments, including homes. They’re smaller, point-of-use units installed beside kitchen dishwashers or used under three compartment sinks. There’re preferred due to their small initial investment and maintenance costs.

Naturally, the passive hydromechanical grease trap has up to 100gpm handling capacity. Any waste exceeding this maximum allowable flow should be left to either the automatic grease receptor or the gravity receptor as they allow for more handling capacity.

Manual grease trap designs date back to the Victorian days. Nathaniel Whiting was the first person to obtain a patent for a grease trap. Grease traps are usually constructed from stainless steel or plastic and must be cleaned occasionally.

How To Install A Residential Grease Trap

Unless you lack basic skills, grease trap installation doesn’t require the services of a professional plumber. A grease trap should be accessible so you can clean it out when it fills up, but the frequency is much lower in homes than in commercial establishments.

Here are the steps to follow in grease trap installation:

1. Determine where to install the grease trap

The most convenient place to install a grease trap is beneath your sink but it can also be installed outside your home. Unless your home has several sinks that are regularly used for cooking, setting it up beneath your sink is recommended.

2. Connect the grease trap

Read the manufacturer’s manual for instructions. While installation may vary from one model to another, most grease traps have three connections.

The first connection connects to the sink or the wastewater source.

The second connection is designed to connect to the holding tank vent. It is however recommended by plumbers to install a cleanout tee before connecting the device to it.

Lastly, the third connection is usually found on the lower right of the grease trap. It is mostly secured to the pipe that leads to the sewage system.

In order to help the grease trap work even more efficiently and last longer between cleanings, it is recommended that you pour hot water on any food or greasy liquid going down the drain.

How To Clean A Residential Grease Trap

This section is intended to help homeowners who have a residential kitchen grease trap with some bits of general information. Before embarking on the process, you’ll need the following items:

  • Oil dry (you can buy it at an auto supply store)
  • 2 or 3 trash can liners (garbage bags)
  • large trash can
  • Proper tools to open trap
  • Paper towels
  • A wooden dowel for measuring
  • Tools for removing contents (scraper and scoop)
  • Rubber gloves

To begin, you’ll need to:

  • Make sure the work area is well prepared
  • Ensure the trash can liners are put into the trash can
  • Add some oil dry. This is essential as it soaks up all the liquid thereby making transportation a breeze.

Now that everything is set, let’s begin the steps required to clean a grease trap.

1. Detach the lid from the grease trap gently using pry bar

Under the cover you’ll notice that there are gaskets.. It’s imperative that you go slowly throughout the process of detaching the lid from the grease trap. Any damage and you’ll need to replace your gaskets.

2. Inspect The Grease Trap

During the cleaning process, you need to be aware of where parts are located and how to install them back safely without damaging them. Plumbers recommend that you have a drawing of the interior so that you have a point of reference.

3. Insert a Measuring Stick

In order to measure how full the grease trap is you need to insert a measuring stick.

Lower it gently and stir lightly so that the debris clearly marks the level. The next step is to remove the measuring stick and record the results in a fat, oils and grease pump out report.

4. Remove any still water using a small bucket

Better still, you can keep the water in a large bucket, and pour it back into the drainage after you’re finished with waste collection.

5. Use a scraper and scoop to remove waste from your grease trap

Remove all solid waste out of the grease interceptor. For easier transportation of the waste you can mix it with oil dry, which solidifies any liquids, including water. Then place the mixture into a heavy-duty plastic trash bag for transportation.

6. Clean the trap sides, lids, and parts

Using a pot scrubber with soap and room temperature water, remove excess waste from the lid and trap sides.

Next, use water to flush the parts and screens in order to get rid of debris and soap.

7. Reinstall the grease trap

Now that your grease trap is cleaned out, it’s time to reinstall it. You can use the drawing of the great trap as a point of reference.

Everything You Need to Know About Plumbing Traps

Plumbers always talk about plumbing traps. It seems grease traps, p-traps, s-traps, drum traps, etc. come up in almost every discussion among professionals. How many times has a plumbing tech stopped to explain what a plumbing trap actually does? Are the installation, products, and supplies a secret of the trade? Well, it certainly shouldn’t remain a mystery.

We’ll explain what a plumbing trap actually does, what types of plumbing traps are available, in what situations people use it, and which traps professionals no longer use. As a result, by the end of this piece, you’ll possess a useful wealth of information. When doing anything plumbing-related, you want to make sure you have a high level of precision. Don’t fear, we can help build your plumber profile! Let me bottle up some tips and tricks for you.

Also, here are some are some great traps you can use:

Basics of Plumbing Traps

Sewage disposal systems produce some pretty nasty odors while other can even come to a point where they are considered dangerous. In order to protect us from these risks, a barrier is placed between the plumbing fixture and sewage waste system. Sewage disposal systems start in the production phase of the shower, bathtub or toilet. Then it enters the disposal stage, sending the sediment waste through a series of inline steps. This helps ensure waste doesn’t overflow.

Common Gases that Are Produced in a Sewage System

Having said that, any plumbing fixture directly connected to the sanitary drainage system must be equipped with a water seal trap. That means every single plumbing fixture used to evacuate waste from a building should have its own plumbing trap.

Plumbing Trap Definition

By definition, a plumbing trap is a device that keeps a small amount of liquid every time the fixtures is used. The amount of retained liquid is called a trap seal. This trap seal prevents sewage system odors, gases, and vermin (mice, insects, etc.) from entering the living or work space.

Trap seal is the maximum vertical depth of liquid that a trap will retain measured from the crown weir and the top of the dip of the trap. The most common of all plumbing traps is the p-trap. This is used with kitchen sinks, lavatories, and laundry sinks. Check out the diagram in Figure #1.

Figure #1 Tubular P-Trap

Plumbing Codes Restrictions

Most Plumbing Codes place restrictions on how a p-trap is used and manufactured. Here are some of those limitations, restrictions, and clarifications.

Figure #2 – P-Trap Level and Not Level

Figure #3 Double Trapped Water Closet

Figure #4 Two & Three Compartment Sink Spacing

The greater the velocity of the water rushing through the plumb fixture drain, the more likely the drain will siphon the trap seal. The vertical drop for sinks, lavatories, showers, and bathtubs is between 18” and 24” but not more than 24”. The shorter the vertical distance, the more efficient the trap functions. Check out the diagram in Figure #5.

Figure #5 Horizontal Distance of Tailpiece Drop

When a water closet has flushed, the velocity of wastewater removes the trap seal completely. The trap seal would remain compromised if the trap seal wasn’t restored by the refill tube on a tank type toilet. Concealed traps used for bathtubs, showers, etc. cannot have integral cleanouts. Check out the diagram in Figure #6 to observe the v parts of a p-trap.

Figure #6 Important Part of a P-Trap

Explaining Deep Seal P-Traps

Deep seal traps have vertical depths of 4″ or more. They are used in a limited number of applications. There are some advantages to using deep seal traps. These benefits are specific to their respective application.

Advantage #1

A deep trap has a deeper seal with more liquid than others. Therefore, the seal doesn’t evaporate as quickly.

Application. Use a deep trap when you install a floor drain in a remote location. This can be a large warehouse. In these cases, the application needs very little water to reseal the trap.

Advantage #2

The deep seal trap has a much greater capacity for resealing. Because the trap is usually quite a bit larger than a traditional trap, it can handle a much greater flow of water. As a result, the trap is less likely to lose its seal because of the extra amount of water.

Application. Use a deep seal trap when a fixture or piece of equipment calls for an indirect waste connection. This can be a commercial ice maker, salad bar or in some cases a triple pot sink.

Advantage #3

Thanks to its depth, a deep seal trap is less likely to lose its seal due to the back pressure or trap siphonage.

Application. There are instances where a fixture or trap cannot be properly vented. In cases such as these, a deep primer seal trap would be ideal. All of the aforementioned advantages apply here as well.

Deep Seal Traps Don’t Work for All Jobs

Here are a couple of reasons why deep seal traps are not the norm for all applications.

What Are the Types of Plumbing Traps that Most Plumbing Codes Prohibit?

Figure #7 Commonly Prohibited Traps

The majority of plumbing codes agreed on avoiding certain types of plumbing traps. These are:

I think drum traps need a little bit more explanation. Codes don’t necessarily prohibit them. However, professionals simply choose not to use them in new construction anymore. Drum traps played their part when installing bathtubs and lavatories. A trap adapter is used in residential and commercial drain, waste and vents systems.

Figure #8 Drum Trap

A drum trap is a circular metal barrel canister with the inlet near the bottom of the trap. The waste outlet is at the top with a removable cover.

Ideally, professionals install the drum trap in a place with easy access. This way, you can remove the cover to clean. Unfortunately, many drum traps we’ve encountered are behind a wall. In other cases, people have it hard to remove the cover which fused together by time. Therefore, when drum traps stop, they are extremely difficult to clear by rodding. That’s due to their inlet and outlet configuration.

Drum traps existed so that people could find jewelry or valuables if lost down the drain. The trap would catch and guard the ring or earring by sinking to the bottom. The likelihood that a valuable would flow into the waste opening at the top of the trap is highly unlikely. A sand trap also helps to separate sand and oxidized organics found in water supplies.

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What Is a Building Trap?

Back in the day, before people used or understood system venting, vermin like rats or insects could move freely from building to building, house to house. Not to mention the sewer gas odor could be unbearable because of back pressure and trap siphonage. Health officials knew that this could pose as a serious health risk, especially in heavily populated, wet, and dry areas.

Therefore, to combat the issues above a house, a building trap is required in each building. The building trap provided a secondary line of defense against the vermin and sewer gas. Most times, the building trap was a large diameter S-trap. Today, most codes do not require a building trap. In fact, in most cases, they are against code.

Figure #9 Typical Building Trap

Reasons Why Plumbing Trap Seals Break down

Trap Siphonage

Trap siphonage can look as a low negative pressure within the fixture drain. However, you can grasp this concept more easily by describing it through a simple visual image. Picture a large amount of wastewater hitting a waste stack at one time. As the wastewater goes by the other fixtures connected to the stack, it can pull the water from their respective trap seals.

Another scenario that could cause trap siphonage is a fixture using an S-trap. If the fixture is full and the wastewater is released, the water will rush through the trap, with the waste pipe carrying some of the trap water. What happens is that not enough liquid is left to form an adequate trap seal. A similar scenario can occur if people install a fixture on a long run of piping with no vantilation. If the water vacates a vent fixture into the trap, it could build up enough velocity to drain the trap.

Back Pressure

Above we’ve described instances when a trap is compromised by being pulled out of the trap. However, there are instances when water can blow of the trap into the fixture. Subsequently, the water enters the building. This can happen when a large amount of waste flows into the drainage system. The water will compress the air in front of it. If the fixture at the point of compression has no proper ventilation, it will blow out the trap.

Shower Leaks Behind Wall: How To Fix Them in 7 Steps

One of the responsibilities of owning a home is maintenance. Often, you may not realize there is a maintenance problem until you see the damage. A leaking shower is not only a nuisance, but can raise your water bill and result in costly repairs.

The shower leaks that you can see are the ones that you quickly notice and are easier to repair. The leaks you cannot see are the ones that are most problematic. Shower leaks behind wall can do internal damage long before you detect them.

Wind Effect

Have you ever been in your bathroom on a windy day and seen the water level in the toilet bob up and down? The same action can compromise the traps in your home. The pressure or suction caused by the strong winds can cause the water to rise and fall into the trap. If the fluctuations are big enough, a small amount of trap seal may spill into the waste system. This incident is going to compromise the trap. As you can imagine, the seal is more susceptible to both back pressure and trap siphonage.


This is a very common occurrence especially in instances where a fixture or drain has a sporadic activity. The water in the trap then evaporates when not in use, at least once a week. Laundry room floor drains, remote floor drains, fixtures and all traps in a summer home are all more vulnerable. Under these circumstances, evaporation has high chances to happen.

Capillary Action

This doesn’t happen often. However, if there is a constant issue with a fixture loosing it’s trap seal, this is something you can rule out. I think an example will serve this concept better than a lengthy explanation.

Figure #10 Capillary Attraction

Maybe a cleaning person runs out of the clean water while mopping a large public toilet room. They may not want to fill up the bucket again. The alternative is that they flush one of the water closets a few times to make sure the water is clean. They rise the mop off in the toilet. One of the strands of the mop dislodges and gets stuck inside the trap seal. The piece stretches to the fixture branch and into the waste system. The water from the trap will pick up the string and into the waste piping, draining the trap seal.

Final Word

Now that the plumbing traps are no longer a secret of the trade to you, you will be able to understand your system better and visualize how it truly works. You can now choose the right type of such a device for your home and make sure you leave no loopholes for a breakdown. If you have any questions regarding this domain, don’t hesitate to drop us a line in the comment section below. You’ll provide additional insight to our readers, and you’ll also get an answer.


In Figure 5, shouldn’t this read “Maximum” distance?

Yes John you are correct it should read “Maximum Distance” Thanks for the heads up.

Maximum distance for the tailpiece is 24″.

What is wrong with a double P trap, and what is wrong with one of slightly larger diameter?

My mother in law’s house is quite jerry-rigged. Her tub (1 1/2″) drains 3+ feet straight down to a 2″ galvanized 8″ deep seal P-trap right at the sanitary tee hub on the main stack. It rotted out and I’m looking to replace it with a PVC solution. Looking up at the basement ceiling, it looks like the bathroom sink and the kitchen sink also drain into this line, and I know both those sinks have p-traps directly under them. But now, with the basement P-trap leaking, sewer smell is present at the kitchen sink and in the bathtub. Seems that a deep seal lower P-trap and regular upper P-traps were doing the job. Pretty sure both sinks use 1 1/2″ pipe too.

Hello I am Naveen. Our customer has done a core cutting with 270 mm distance from the wall where as the S trap distance of the closet is just 210 mm. Is there any way it can be brought to 270 mm. Is there a product to cover the distance of 60 mm

Wow I’m gonna have to think about it for a minute. A closet bend would get help you if you were 12″ to 36″ of but you’re just 21/2″. That is such a tight offset. If it were me I’d probably remove the toilet and reset if possible. Is this a basement foundation core? Wall? What floor? If you can snap a few pictures so I can see the layout.

I am planning to close a toilet and instead modify the plumbing to connect to a washing machine. Is it advisable to make the modification ?

There is no inherent reason why you can’t cap off the waste from a toilet and use the waste piping for a laundry. I would say you should try and dump the laundry waste as close to the end of the waste run as possible. You don’t want a dead leg at the end of the waste line, it’s not the end of the world but you want to try and minimize. Just remove the toilet and closet collar if you can, stuff the pipe with newspaper or burlap and pour concrete over the top. 2″ to 4″ should suffice.

hi,in my building combord pipeline,sink pipeline and waste water pipelines in toilet are joined together by means of a deep trap plumbing it advisable?.in general people are questioning how can you join both combord line and waste water line.odour will come through waste water line?.please clarify

I have never heard of the term “combord” before so I can’t answer your question. Please clarify and I’d be glad to help.

Can a washing machine and a nearby sink share the same P trap?

Thank you for your advice

No each plumbing fixture or appurtenance shall be trapped individually.

I’m adding a prefab shower in a tight space upstairs–the drain has to fall over a 2×8 joist ,which i notched a bit to get the drain body to sit where it needs to be..this means I have to offset the tailpiece a bit to connect to the trap (in other words it isn’t straight out of the drain body like all pictures show) –we’re only talking about a 2-3″ offset to reach the trap.. is this going to be a problem?? Thanks…

Wanting to hook up a single line to a sink and washing machine.
Was planning to have a P-Trap for both , the washing mashing is first in line and more then likely the most active of the two!

My question is ” Will one P-Trap create suction on the other causing it to drain out? “

@Dan good question. Most codes read that each plumbing fixture shall be individually trapped so two traps is the right way to go. I do not believe if the fixtures are vented that you run the risk of siphoning a p-trap.

Awesome thank you for the peace of mind.
I have ran two P-Traps and so far so good as the washing machine line is also acting as a vent too…

need to hook up utility tub for washing machine,can i use building/house trap as drain?

You can tie into it however the utility sink must be independently trapped.

is there a diameter difference in piping/water traps between european sink standard and USA? I have read some materials that e.g. bathroom vanities from European market cannot be (or have hard time) to be applied to US norms.

Have you heard anything about it?

There are several difference actually. #1 in Europe water piping is sized in millimeters by the outside diameter or O.D. in the U.S. water piping is sized in inches using the nominal dimension which is the inside diameter. When using European faucet in the U.S. there are usually adaptors included so that it can be made to work.

I was wondering if a p-trap has to be set straight up and down or if it can be tipped onits side a little bit. So I dont have to cut hole in floor deck.

The p-trap must be installed horizontally with the trap straight. If you do not you will almost certainly lose your trap seal.

I installed a deeper kitchen sink and now my trap is about 2 inches lower that the outlet. What can I do to reconnect it. Thanks.

Cut kitchen tailpiece that drops directly down from the sink 2″ and reinstall. That will raise the kitchen waste piping up 2″ so you can connect it to the waste opening.

If I dropped a ring down the sink, how long will it stay in the P-trap? It happened a month or two ago. I have been using the sink, and figured it was gone. Someone told me it may still be there, but someone else said, “if you don’t get it right away, once the water flushes through, it will be gone.”. which statement is true?

The truth is if the ring is heavy enough it will probably still be in the p-trap. It really all depends on the weight of the ring and the speed of the water going down the drain. If the water is slowed down by a pop-up drain there is a good possibility it’s still there.

Hello, I have been told that for a tub you need a specific tub Trap, is this true? And if so what are they called?
Thanks so much.

You need a waste and overflow drain with a p-trap. The p-trap is a common p-trap nothing special. The connection to the material you are using for the Waste and Overflow will determine the type of connection but other than that you’re good. If you’re in a hi-rise building hit me up again.

Perfect. Thanks, sir.

You are welcome. Thanks for stopping by.

I have a 1st story bathtub with a 1-1/2″ PVC P trap connected within 18″ to a 3″ cast iron waste stack and vent. The waste stack runs to the basement and changes from 3″ to 4″ cast iron 3 feet above the basement concrete slab. There is a P trap in the 4″ cast iron under the basement slab. Is this situation considered a double P trap or does the 3″ vent stack between the two traps negate this problem? I am going to renovate the bathroom, but prefer to not rework any of the waste lines since all of the fixtures are going back into their original locations. Thanks!

You really have to check with your municipality. We haven’t put house traps in, in the Chicagoland area for over 50 years. My house in a Chicago suburb doesn’t have one and it was built in 1955. From a functionality standpoint the vent would take care flow or back pressure issues so I wouldn’t remove it, it’s not necessary. From a code perspective if it’s illegal in your town the house would be grandfathered I would imagine.

My tub drains into an elbow then into the waste line. I smell sewer gas whenever the shower is used. Several plumbers I have called in and they are adamant that the elbow joint is a trap, I know they are wrong, a downward bending Elbow can not be a trap. Who is correct ?

So the tub drains directly into a 90 and that connects to a branch waste line? I’d love to see a picture if you have one. It’s hard for me to believe that two different plumbers got it wrong. Are you sure that someone didn’t make a trap from fittings? Let me know I’d like to see it. [email protected]

My outlet pipe to my s bend in my kitchen is too short….
How would you recommend fixing this – apart from getting another s bend? It’s literary only short 2 millimeters.

S-Traps are illegal in most areas in the US. Because of your use of a metric measurement I assume you’re outside the US. The only way to fiz this is to purchase a new S-trap.

I am installing a shower in a first floor location that is cantilevered out from the house. The floor joists are 2 x 10s and the joist cavity is insulated. Problem is the P-trap almost touches the bottom of the joist cavity and is likely to freeze being very close to the exterior of the house. If I install a trap inside the house proper (a running trap) freezing will not be an issue. The run from shower drain to the trap would be about 4 feet. I do not know why codes do not allow running traps for this kind of application. What kind of problems would a running trap, in this application, be likely to create? Thanks.

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Running traps are illegal in most municipalities. If this were my house I would install the p-trap where it is supposed to be and run heat tracing tape around the p-trap. This way in the winter it’s always kept warm.

It’s not what we use on the commercial/industrial side but this more than adequate.

Can I have any amount of straight pipe for the bottom of the trap for my kitchen sink?

I don’t quite understand the question. Are you talking about the horizontal piping from the trap to it’s connection to the waste branch or the vertical drop from the waste outlet of the sink to the trap? The maximum length of a drop from a sink to a trap is 18″ and the maximum length of horizontal 2″ waste piping to it’s connection to a waste branch is 5ft.

Can anybody give me an answer, the p trap in my basement utility rm has a p trap with a 3 slotted vertical spacer in it. What is the purpose? It is not draining the condensate from my a/c coil.

Can you please take a picture and send to [email protected]

A slotted tail piece or indirect funnel interceptor on a p trap was used for something like a drip condensate drain or similar device. It is normally open to be able to visualize that the drain is plugged or stopped up.

and to spill out on the floor if a backup occurs. There is a natural air gap when an indirect waste is installed.

I am removing a bidet can just cap the hot and cold copper water lines and the drain(which joins the toilet drain line leading to the basement.

Yep you can cap all three.

I am installing a new tub with 2″ drain. Is there anything wrong with running a horizontal line with(1/4″ drop per foot ) about 2 feet before adding the P trap ?
Because of space their isn’t much room to add it right below the drain.

Most state codes state that no traps shall be more than 18″ away from the fixture being served. Please check your local codes for the most accurate information.

Thanks. I’m in a highrise. I am running a linear drain with a horizontal outlet (instead of vertical) as this allows me to not have to break a hole in the concrete floor and access/install plumbing in the apartment below mine.
Coming out of my linear drain, I will run my 2″ PVC about 12-16″ horizontally (with 1/4″/foot slope) into the chaste, and there I will put the trap (and connect vent pipe as well in the chaste). Can you please send me info/code requirements for this horizontal run before installing p-trap? I know most shower drains are trapped directly below the drain, however, my application does not allow for this configuration, therefore, I want to find the appropriate codes to support my configuration. Does this make sense, or am I leaving out any relevant details?

There really isn’t a maximum distance between plumbing fixture and trap. In Chicago’s code on page 99 it’s states “trap shall be installed as close to the fixture as possible” The issue becomes the distance between the outlet of the fixture and weir of the trap. That can’t exceed 24″. That is universal although you can read it in the Chicago Code.

If I want to permanently remove a tub, would I have to cap off the drain under the p trap….it is under the concrete slab.

Remove the tub, cut the waste off flush to the floor, stuff burlap or newspaper into the waste opening and fill with concrete for a few inches. You may have to grind down the waste piping a bit to get it flush with the floor but it’s not too difficult.

Remove the tub,pull out the tailpipe and screw a test plug in the pipe below the floor. Because if the pipe ever stop up or back up it wouldn’t come back out your pipe,and cause you a problem.

Hi! We have a 4″ concrete slab with a drain pipe with no p trap. Are there any kinds of bathtubs that have a p trap built in (kinda like a toilet)? Or do we need to put the tub on a platform highbenough for a p trap under it? Cutting the concrete is not an option. Thanks so much!

This is a great question because we have always done the latter. We put the bathtub on a platform so the p-trap fits underneath. I did do a little research and to my knowledge there are still no manufacturers that make a bathtub with an integral trap. If you do run across one please leave a link in this thread.

Can you instal 2 50mm traps to another 50mm trap on the same line

No wasteline or plumbing fixture should be double trapped.

Thanks for writing good information all about plumbing traps.

Can someone explain to me what a “tea kettle” trap is?

I have never heard of that term used before. It could possibly be referring to a drum trap.

rental property that has had several main waste line backups over last 2 to 3 years. In just about half the cases, maybe 8 to 10 now over 3 years, we have found evidence that things being flushed that clogged the lines (ie., tampons, feminine pads, baby wipes, grease) but recently we have been stumped that it seems like every few days we are noticing a slow flow as if normal waste or toilet paper is backing up the line. We have easily remedied the backup by snaking at the house trap (just inside the foundation wall) which is buried in the basement floor, but the cap is accessible. We have had this property for going on eighteen years now and are beginning to wonder, ether the trap has deteriorated or become full of sediment or otherwise compromised. We are still trying to find the right equipment to maybe camera or scope out the trap, as this seems to be the area that once snaked, quickly relieves the back up. Any experience or suggestions welcome. thanks!

You most certainly need to camera the sewer line. There is probably a dip or a separation in the piping that is causing things to hang up at the same spot. We use a Rigid Sea Snake. I’ve used plenty of other units but this is still the Cadillac of sewer cameras.

Thank you for the helpful info! We are in the middle of having a washer installed…the plumber installed most of the plumbing and left it over the weekend, to be finished later this week. Over the weekend, a distinct sewage smell and flow of air was coming out of the open standpipe and we noticed that no p-trap was installed at the bottom.

We asked our plumber and he said that “that type of piping doesn’t need a p-trap” and he’ll fix it so that it doesn’t smell anymore. Is this a legitimate practice, i.e. is there any setup where a p-trap wouldn’t be needed?

A washing machine standpipe should be trapped and be within 5ft of a vent. If not the line should be independently vented. That is a false statement.

Thanks for asking.

Not sure if you can help me as I’m doing a kitchen reno atm. When the S trap is in place the water would back up into the dual sinks. I removed the S trap and plumbed directly into the waste pipe and never have a problem with water backing up. Is there another option or is there a reason this is happening?

S-traps are almost completely obsolete. You should remove the s-trap and add a p-trap. If you have already done so you’re in good shape if not you most certainly need one. As to why it backed up I’m not sure. It could be that the trap was obstructed.

I’m installing a pedestal sink in a bathroom. The drain is 1 1/4″, therefore I’m assuming the trap needs to be 1 1/4″ as well. I’d like to increase the pipe size as soon as possible after the trap. Is there a minimum or maximum distance required before increasing pipe size?

Hi! would I be able to install a sink from water line that used to be a shower? Do you need to change the trap? or would the same trap work for the new sink?

You can absolutely use the water supply that used to service your shower. You cannot, however, use the existing trap. The maximum distance between the sink drain and the p-trap is 24″.

does there need to be a trap in the 4 inch waste line from my bath to the main sewer if the appliances in the bath are trapped. the trap that is there now has waste from the commode floating.

I’m not sure I understand the question completely however I will give it a try. Most plumbing fixtures are trapped and most municipalities do not require the house to be trapped (There are some, Lancaster PA is one that still requires a house trap) So it’s most likely you do not need a trap on the 4″ line. The thing that is throwing me off is that you reference appliances in the bath and that there is raw waste in the water closet. I’m not making the connection to the two fixtures. They should both be independently trapped.

Is there a problem with having a 4-foot vertical drop from a water closet before to starts to run horizontally. I cannot find where this is prohibited by code, but it seems like it could siphon the water out of the bottom of the toilet. Also seems like the liquids could out-run the solids and create buildup in the vertical section of pipe.

The maximum vertical drop from a trap is 24″. All of the concerns you mention are valid for sure.

Are round bottle traps allowed by code in California?

Hey John, thanks for reaching out. I’m not super familiar with California’s plumbing code although I did go through it and didn’t find a section mentioning disallowed traps. It may be I don’t know where to look. I’ve reached out to a friend in Cali to get a definitive answer. Bottle traps are not allowed in many municipalities across the US. I will have an answer for you shortly.

Thank you for your follow up.

My Indian toilet has backwater from the septic tank as the toilet outlet pipe in below the septic tank level. What should i do? Should i install a Western toilet with some kind of backflow stopper? Will it help? And how should i seal my Indian toilet? Please help.

I don’t think your Indian toilet is the issue. May I ask where the heck did you purchase an Indian toilet in the US? There aren’t many distributors here in the states and certainly no fixture manufacturer based in India that have gained a foothold. To my knowledge, there are no toilets that have an integral check valve. You could install a water closet with an ejector pump that sits above the floor like this

And then pipe it back into the waste line. This way your water closet is divorced from the waste line. It’s basically a forced main.

I am responsible for maintenance in an apartment building that is nearly 20 years old. Whenever a resident moves out, one of the many things I update is to switch the original chrome plated p-traps serving the kitchen (1.5″) and bathroom (1.25″) sinks to plastic.

I have noticed that at least some of these plastic traps come loose over time and leak into the sink cabinet, causing serious damage to the cabinets and rollout drawers. This is an expensive problem, especially if it is widespread.

Can anyone explain why plastic traps come loose over time? My hypothesis is that the expansion and contraction effect of running hot and cold water causes the threads to loosen ever so slightly upon contraction, but shouldn’t this occur with threaded metal pipes also? My experience with chrome plated metal pipes is that when they leak, it is due to physical damage or rusting out from the inside, hence the reason I have been switching to plastic.

The domestic hot water in my building is communal and capped around 120-125 F by the mixing valve so supply water is not particularly hot, although residents who regularly boil pasta, eggs, etc. can introduce much hotter water to their drains. I see this loose trap phenomena most often at the kitchen drains–which fits my theory–but it has also occurred in the bathrooms as well.

Should I be performing a periodic trap inspection? If so, how often is recommended?

I have been using basic plastic drains from HDSupply exclusively. Should I try a different brand of plastic drain?

Thank you for reading this; I appreciate any insight you can offer.

This is a great comment and observation. I don’t want to sound wishy-washy but both work well depending on the type you use. I agree with you that most chrome plated p-trap I’ve replaced are replaced because of deterioration. The joint is fine but the metal has corroded and worn away. However, when you invest in something like the Brasscraft or basically any p-trap or tubular products that are 17 gauge will give you the durability and rigidity you’re looking for. The same is true for plastic fittings. Most plastic tubular p-traps you buy from the home centers are not heavy-duty which makes them way more susceptible to heat. Pay the extra money for commercial grade tubular p-traps. Having said all of the above the biggest issues I’ve experienced with leaking p-traps is with homeowners store things in the cabinets containing the tubular fittings. As people pull out and put back cleaning supplies and other things they hit the trap compromising the joint. Tell people to be careful if they are going to store things in the cabinets.

Wow, this blog is so fantastic. There’s so much great info here. I work in the grease trap industry, but this is such a great resource to send people for those that want more in-depth knowledge about drainage and plumbing.

Thank you so much. Tell me more about your business. I’ve certainly put in and worked on enough grease traps in my day. Rodding super grease traps are super fun. I think I’ve mentioned that before.

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