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Brian, Architect
Category: Plumbing
Satisfied Customers: 3123
Experience:  Licensed Architect- 17 years
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I have water bubbling up in my toilet when I drain water ...

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I have water bubbling up in my toilet when I drain water from the kitchen drain only in the summer time. Also when I turn on my air conditioner, my house smells like a sewer. No problem in winter time though. After the water bubbles up, then I have to wait to flush toilet for a while and then it flushes fine. We had a new toilet installed about a year and a half ago, problem ever since.


Welcome to Just Answer.

The toilet or main drain pipe can be partially clogged or the main vent pipe can be partially clogged from an animal getting caught or a bird building a nest, etc. You should try snaking both with a plumbers snake, to clear any blockages.

A high pressure nozzle, on the end of a water hose, can be used up on the roof to spray down the main vent pipe. This is effective at clearing blockages in the vent pipe only. Watch the short video below, to learn more about plumbing vents and how to clear them.


As far as the sewer smell after turning on the air conditioner goes, it is most likely one of the following:

  1. Sewer gases can come up thru a sink drain if the trap below the sink is not full of water. Using the sink regularly is what keeps the trap full of water. If the sink is not used often enough, the water in the trap can evaporate, allowing sewer gases to flow past it. Often, if there is a problem with the plumbing vent, such as a partial blockage, or the vent is installed incorrectly, the water can actually be siphoned out of the trap, allowing the sewer gas to escape. If the smell is recent and the sink has been in place for a long time, then it would be safe to say that the vent was installed properly. I would go around your house and run the water at each sink, shower and tub for 10-20 seconds to make sure all traps are full
  2. The smell could be coming from the wax seal located at the base of any of your toilets, in which you would just have to remove the toilet and replace with a new wax seal.
  3. Highly unlikely, but it could be coming from a loosened/ disconnected joint in the vent system, in the wall. Unfortunately these are not easy to find without removing the portion of wall where the fixture drain enters the wall. Before doing this I would check all visible joints, between the trap and the wall, and then see if the odor is strong where the pipe enters the wall. This would be a sign of a loose joint behind the wall.

The air conditioner is simply moving air around and making the problem more noticeable; when the A/C is off, the problem is still there, just not as noticeable. The first thing to do, is to really try and narrow down where the strongest smell is and where it is coming from; do this when the A/C is first turned on. This will help tremendously and once this is established, the things discussed earlier can be used to further find and ultimately fix the smell problem.



If you need further help or clarification on this answer, please reply to this post.

Best of Luck, Brian

Customer: replied 8 years ago.
Reply to Brian's Post: The smell comes up thru the vents in the floor from the furnace especially the cold air vent in the bedroom.

This is the perfect clue!

I can guarantee that if you inspect the bathroom that is closest to the return air grille, that you will find the smell problem.

I have seen this time and again, because the return air grille is sucking air to the furnace/ air conditioning and re-distributing that air throughout the house floor vents. Just to test it, try spraying some non-flammable air freshener near the return air grille......within a few minutes the whole house will smell nice.

So back to the inspecting......the nearest bathroom needs to have the traps filled with water by running the faucets and gently wiggle the toilet to see if it moves. If the toilet moves, it is a good sign that the wax seal is leaking sewer gases and needs to be replaced. Replace the seal and the smell will be gone.




If you need further help or clarification on this answer, please reply to this post.

Best of Luck, Brian

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