When everything is working properly, your plumbing shouldn’t smell. If you start smelling sewer gases coming from any drains or elsewhere in your home, it’s an obvious sign that there is an issue with your plumbing and drains. Some of the issues that can lead you to smelling sewer gas odors are easy to fix, but others will require professional help. We’ll explain the reasons why you might smell sewer gas in your home and how to know if you need to hire a plumber.

1. Dry Plumbing Traps

If you suddenly smell sewer gas wafting up out of just a single drain, it most commonly means that the trap underneath the drain is dry. Every drain in your home, including your sink, shower and floor drains, has a special piece of pipe just underneath it known as a P-trap. A P-trap is a short, horizontal pipe that has a big bend in the middle. This bend constantly stores water, which creates an airtight seal that prevents sewer gases from rising through the pipe and out of the drain.

If you don’t use a plumbing fixture for some time and no water goes down the drain, all of the water in the P-trap can evaporate. This means that the pipe will no longer be sealed off and sewer gases will start floating up out of the drain. It typically takes three to four weeks for a trap to fully dry out, but it can happen more quickly in the winter or any time the air in your home is much drier.

There are times when a P-trap will continuously run dry and the drain will smell like sewer gas after only 24 hours or so. This typically happens because there is lots of hair or other debris stuck in the bend of the trap. Not only will debris in the trap prevent it from holding as much water, but it can also wick or absorb the water so that the trap isn’t fully sealed. You may be able to use a plunger to clear out the pipe. If this doesn’t work, the best option is to have a plumber clean out the debris with a pipe snake. We wouldn’t recommend using any type of drain cleaning product since they all contain extremely caustic chemicals that can do severe damage to your pipe and drain.

Strong gusts of wind can also force lots of air down the vent stack pipe on your roof. The air can flow through your pipes with enough force that it disturbs the water in the trap, causing it to slosh out so that the trap no longer has an airtight seal.

Any time you ever notice sewer gas smells coming out of a single drain, you should try and turn the water on for around 15 seconds to fill the trap back up. If you smell sewer gas from a floor drain, you can just dump a few cups of water down the drain. If the sewer gas odor was caused by a dry P-trap, the smell should dissipate almost immediately. If you have any plumbing fixtures you rarely use, you can also easily prevent them from smelling like sewer gas by making sure to put some water down the drain every week or two.

2. Clogged Vent Stack

The plumbing vent stack that extends up above your roof serves two essential purposes. The first is to prevent sewer gases from building up in your pipes, as all of the sewer gases naturally rise through the stack and out of the vent pipe. The vent stack also allows air into your plumbing system so that all of the pipes drain properly. Any time you flush a toilet or drain a sink, the force of the water moving through the pipes pulls air in through the vent stack.

The vent stack can sometimes get clogged with leaves and debris, especially if it doesn’t have a cover. If the vent stack is clogged and no air can get drawn in, a vacuum can form inside the pipe so that it doesn’t drain properly. Since no air can get drawn in through the vent stack, air will end up getting drawn in elsewhere such as the through sink, shower or floor drains. When this happens, it can end up pulling the water out of some of the P-traps in your home, causing them to go dry and allowing sewer gases to come up out of the drains.

If a clogged vent stack is the reason you keep smelling sewer gas in various drains, you’ll usually also notice other issues such as chugging or gurgling sounds when you flush your toilet or drain a full sink. One fairly certain sign that the vent stack is clogged is if your toilets keep going dry. If you notice these issues, you’ll need to have a plumber climb on your roof so they can inspect and clean out the vent pipe.

3. Clogged or Leaky Drain Pipes

A damaged, leaky drain pipe can also allow sewer gases to escape. However, this normally only happens if the main drain pipe that extends into the wall is leaking or if there’s a leak in the connection between the P-trap and the main drain pipe. These issues should be easy to spot since you’ll usually see standing water or water damage underneath the sink.

A partially clogged drain can also start giving off an unpleasant sulfur odor. When there is lots of hair, food waste or other organic matter inside a drain, bacteria will start feeding on it and causing it to decompose. In this situation, you can usually get rid of the smell by filling the drain with vinegar and baking soda. You should let the mixture sit for at least 20 minutes and then flush the drain with lots of hot water to wash all the decomposing waste out of the pipe.

4. Broken Pipe in the Drain Stack

If you smell sewer gas in various parts of your home and it doesn’t seem to be directly coming from a drain, it usually means a crack or leak in the drain stack. The stack runs vertically throughout the entire building and connects to the vent stack in the attic and the main sewer line underneath your foundation floor. If you suspect that the stack is leaking, a plumber will need to go on the roof and extend a camera through the vent pipe to inspect the entire stack for leaks or damage.

5. Broken Wax Ring on Toilet

All toilets have a wax ring underneath the bowl that seals the toilet to the drain pipe. If the wax ring is broken, water can slowly seep out and cause the trap inside the toilet to dry out. A broken wax ring will also allow sewer gases to escape out of the drain pipe. This issue is also quite easy to spot as the water will eventually start damaging the flooring around the toilet or cause the floor to feel spongy or soft. If the wax ring is broken, a plumber will need to fully remove the toilet and replace the ring.

With over two decades of experience, We Care Plumbing, Heating and Air is the company to turn to for all of your residential and commercial plumbing repair, installation and maintenance needs. Our team is available to help 24/7 should an emergency arise, and we’re also the top choice for heating and air conditioning services in Temecula, San Marcos, Orange, Murrieta and the surrounding areas. Give us a call if you have any questions or to schedule a plumbing inspection or any other service.

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