Tag Archives: sewer gas

Improper Venting can Actually Destroy a Toilet Trap

Most people don’t really understand how their toilet works, and most people don’t really need to understand it. When something starts to go wrong though, it can very helpful to know what’s going on so you can try & fix the issue yourself. We know plumbers are expensive and you shouldn’t call a company like us if you don’t need to or if it’s something you can fix on your own.

Plumbing is all about moving water from location A to location B. The fundamental purpose of plumbing is to direct, deliver and get rid of water. In the process of doing so, there are many chances for air to get involved and to actually disrupt the movement. A pipe is never empty, even if there is no water flowing through it. The pipes in your home are always filled with, you guessed it, air. When we introduce water into a pipe, we are pushing out the air. The air is not going to just disappear so we need to find an easy access for the air to escape while keeping the water in the pipes. And to complicate the issue, we want the air to escape without letting nasty sewer smells into a house.

The Relation of Air and Plumbing Systems

For every drain in your home, an arrangement has to be made so that the air in your waste water pipes doesn’t come into your house. In one of the cleverest inventions in plumbing, the problem is solved by making sure there’s always a barrier of water between the fixture and the waste line. This is accomplished by something called a trap, usually a ā€œUā€ shaped pipe (but sometimes ā€œPā€ shaped) right underneath the drain or, in the case of your toilet, inside the base of the fixture that always has a few inches of water trapped in it.

The vent system manages air on the downstream side of the trap which, especially in the case of the waste line from the toilet, does not smell very pleasant. As the water and everything in it rushes from the toilet, the pushed air ahead of it comes to a vertical pipe. Water and waste falls down, and air and smells go up the vent stack through the roof and into the outside air. Air is lighter than water so you will never have a situation where waste water is spouting out of your roof. That would be bad. Once the water has gone by, air is reintroduced from the vent stack preventing the creation of a vacuum. Air goes out and air goes back in. When there’s no water being drained, the vent stack passes smells and sewer gas straight up and out.

Sometimes there’s a problem in the vent system usually because there’s a clog up above the roof, like a bird’s nest or leaves stuck in the vent stack. We have even seen instances where tennis balls and baseballs have been lodged in there.

A quick note, the weirdest things we’ve seen blocking the vent stack are as follows: a Barbie doll, a plastic piggy bank, and a Bart Simpson figurine

When that happens, no air is reintroduced. The resulting vacuum provides enough suction so that all the water is pulled from the trap. Two things can happen here:

  1. Option A: The toilet bowl has all water sucked out of it and the sewer gas easily escapes. The toilet bowl doesn’t fill up with water and the missing water that’s supposed to provide a barrier to sewer gas instead allows the gas to escape through the toilet into your house.
  2. Option B: The trap is pulled down enough to make the toilet gurgle and spit water. The air bubbles that will explode from your toilet will be sewer gas and will smell. An improperly vented pump is usually the cause for the “Option B” scenario.

How Can This Happen

ll of the plumbing in your house needs air. When we flush a toilet and introduce water into the system, the air that is present in the system needs to be displaced and usually does so through the vent stack. If that stack is blocked, the plumbing system still needs to pull air from somewhere and will do it through the first available source, which for the purposes of this post can be a nearby toilet. When you think about it, the toilet line itself is a “vent” coming off of the main sewer pipe. What makes this vent different is that is it covered by a toilet. If there was no toilet, the toilet vent line would function the same as your roof vent and pull air into the system.

Why Is my Toilet Breaking?

The trap in a toilet is basically a flap or seal. There is no fancy engineering there but it is quite a useful device for keeping the water in as a barrier to the bad sewer odor that no one wants. If your vent is not clear and your system keeps trying to pull from your toilet “vent”, then the flap or trap will eventually degrade and allow water to leak out of it. You know there is an issue if your toilet periodically turns on & fills up the reserve tank with water. If that happens, it means there is a leak in the trap. Note that a leaky trap will not always release sewer gas. The toilet plunger in the tank is going down to a level where it thinks it needs to refill itself. If you don’t fix the vent, you can burn through a few toilets a year. Pretty expensive considering toilets average around $300.

I’m Tired of Replacing My Toilets. What Can I Do?

If you notice the symptoms of poor venting (smell of sewer gas and/or toilet bowl completely drained or periodically draining & refilling itself) there’s some chance that you can fix the problem yourself.

Grab a Ladder

Most of your vent stack is inside your walls, but where it comes through the roof you can get access. Get on your roof with a flashlight to see if you can spot anything foreign in there.

Be Careful

Exercising all necessary caution you can climb up on your roof and inspect the top of your vent stack. Make you are doing this with a partner. Never go onto your roof alone.

Locate the Clog

If you notice any blockage or obstruction, remove it. This is not always as easy as it sounds so you may need to get creative. Depending on the age of your house and the purpose of the vent, your vent stack can be small. A sewer vent (soil stack) is usually 3″-4″ in diameter where other vents are usually 1 1/2″. If you have multiple vents on your roof, the largest one is the one you should be fixated on.

Call a Plumber

If there’s no obstruction or the problem’s not solved, it’s probably time to call in a professional. A master plumber will be able to identify the issue and recommend the best course of action. At this point, it could be clogs in the outgoing sewer line itself, an improperly ventilated basic pump, a covered street vent, or cracks in your sewer line.

If we missed something here or of you have an interesting venting experience that took months to pinpoint and solve, we’d love to hear about it.