Where Is The Sewer Trap In A House? How To Find The Sewer Trap Location In Your Home

Sewer Service
May 31, 2013

by David Balkan

main house trap that is double vented

Many people frequently have house sewer line or drain issues that get exasperated because they don’t know their house sewer trap location. Knowing where the sewer trap in a house is located is typically the first vital step to uncovering a drain or sewer issue. Sewer issues can range from needing a simple drain cleaning to solving foul sewer smells and basement flooding.

There is a simple process to find the sewer trap location and expose it before drain issues arise, and we’re going to explain it to you. This is something every homeowner should take a few minutes to learn before they are in a distressful situation.

A process to find your sewer trap location

The easiest way to find the sewer trap is to locate the fresh air inlet pipe which is typically located near the front wall of your house. The fresh air inlet outlet is also on the outside front or the side of your home, and it will be exposed and covered by a grating.

locate your house sewer by locating the fresh air inlet first.
Fresh air inlet plate located outside a house

The grating on the fresh air inlet is usually around 9″ or 10″ wide and perforated to allow air to enter the drain system. In some cases, the fresh air inlet for the house sewer will be a U-shaped pipe pointing down at the sidewalk. In either case, the purpose of the fresh air inlet remains the same, to allow air to enter drain pipes and for the free flow of waste water.

The fresh air inlet pipe itself is typically at least 3″ wide or 1/2 the size of the house drain, whichever is greater, but never smaller than 3″. Once you locate the fresh air inlet pipe inside your house, you should be able to find the sewer trap location on the street side of the inlet.

The fresh air inlet pipe is connected just behind the house trap and is usually covered by a perforated plate on the outside of the foundation wall.

Can you connect drain lines to your fresh air inlet?

Please note that it is illegal and a code violation to have plumbing fixtures connected to a fresh air inlet. On occasion, a house sewer may have such an improper connection and it should be removed and legalized. It is also likewise against plumbing code to have any drain line connected to the cleanout on top of a drain or sewer trap.

Find your sewer access pit to know your sewer trap location

There must always be ready access to the sewer trap and access pit. Having a buried sewer clean-out or a covered clean-out will prevent you from finding the sewer trap location, or a drain line location. In addition, if the trap cannot be accessed for cleaning or to check if the sewer trap is sealed properly it poses serious issues.

If the access pit or house trap is not sealed properly foul sewer gases and waste water can escape into the house. It can also become a source of rodent or insect infiltration.

Another important reason the access pit must be accessible is that frequently the water service line enters the house into the same pit and the main control valve for your water line will be in the pit. Having access to your main control valve is vitally important in case you have a water line emergency or a leak inside the house.

In some cases, a homeowner or contractor may place flooring or concrete permanently over the access pit for the sewer trap. This is a mistake and must be removed immediately.

Why is a fresh air inlet for a drain system so important?

Another point about your fresh air inlet is that it helps wastewater flow smoothly out of the drain system. It is as if you tried to drink out of a bottle and completely covered the opening not letting any air into the bottle. Your drink would come out in fits and bursts, not in an even flow.

Air is needed to displace the fluids that are flowing out or it will disrupt the flow of the water. This is also why when routine maintenance is required, always make sure that the fresh air inlet is also clear and unobstructed. The fresh air inlet cover plate should also be clear and not covered with leaves, dirt, or debris. The fresh air inlet should also have a perforated cover to protect it from birds, small animals, etc. entering into the drain system.

Why is a sewer trap so important?

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 or damage if it is not functioning properly, is in poor condition, or if it’s not maintained properly.

Improper Or Missing Sewer Trap Plugs Or Caps

  • This will allow noxious gases to escape into the premises from your sewer line.
  • Allow for rodents and insects, but not alligators, to enter the premises.
  • Can allow raw sewage to enter a premise if a backup occurs.

Trap plugs or caps cost around $15.00 to $25.00 each. They are made in at least three varieties and are readily available from any plumbing supply or local hardware store. You can easily install new sewer plugs or caps on a house sewer using basic household tools or they can be installed by your plumber.

How to replace sewer trap clean-out plugs

Whoever takes the time to install a sewer new plug or cap will be paying a small price for preventing damage, inconvenience, rodent, or pest infestation. In addition, and perhaps most importantly, this minor maintenance can prevent an unhealthy condition and noxious sewer gases from entering your property from your drain line.

Replacing missing or improper sewer trap plugs is another case where performing minor plumbing maintenance is well worth the effort.

About Balkan Sewer And Water Main Service

Balkan is a family-owned and operated NYC water main and sewer contractor trusted for over 70 years. Our website provides access to knowledge, tips, and services to property owners and professionals daily. To learn more about your drain system read Know Your Drain Hardware.

In addition, online inquiries of all sorts are typically responded to within one hour with expert advice and information. Team Balkan is dedicated to serving you in any way possible and guiding you through any water main or house sewer line issue you may have.

Get A Free Quote
David Balkan

David Balkan is the CEO of Balkan Sewer And Water Main, the largest and most trusted service in New York City. David is extremely active in various NYC plumber organizations being the Chairman of the Subsurface Committee in the Master Plumbers Council, and Vice President of the Subsurface Plumbers Association. In addition David’s expertise is respected by officials of New York City agencies such as the NYC DEP, NYC DOB, and the NYC DOT. He frequently provides valuable input on a variety of industry related matters.

Ready to Get Your Sewer or Water Main Issue Fixed?

Get An Instant Quote
  • We manage every project from start to finish
  • We work quickly with instant quotes & rapid responses
  • We are licensed as a Master Plumber
  • Our GPS fleet ensures we are on time, every time
  • We are available 24/7 for emergencies
  • We back all replacements with a 10-year unconditional guarantee