My toilet sometimes runs intermittently after the tank has been filled for a few seconds and then stops also there's a terrible smell a gas smell coming from the bathroom.

I think the problem is related to the wax ring around the toilet bowl because the toilet now moves when I sit on it which it did not always do so my thinking is the wax ring needs to be replaced.

  • 1
    1: Toilet bowl now moves- check the screws mounting it to the floor. Where is grants solution ? Not on this page.. Check the toilet for cracks at the base.
    – Ken
    Dec 2, 2017 at 10:24

4 Answers 4


The flap may not be seated well at the bottom of the tank. So the first, and cheapest step is to replace the flap. However, if you've been adding tablets or chemicals to the tank, those can corrode the PVC fitting (flange) where the flap seals. In that case you need to replace the PVC flange.

The smell is a second issue. That has to do with sewer gas getting into the room. The other answers suggest the wax ring. That might be right. Does the commode wiggle when you sit on it? If it seems steady, it might come from a dry trap elsewhere in the room. If you have a sink or tub that isn't used much, make sure you periodically pour water down them. This puts a gas barrier in the trap, without which, gas comes into the room.


If the toilet rocks when you sit on it, the floor is not truly level and or lacks structural strength or both. I like the new rubber sealing rings. I think they do a better job. But if you have odor problems, the solution starts with quality flooring.

  • Regarding the intermittent water running, I suspect that you need to replace the fill valve,
    – Paul Logan
    Dec 2, 2017 at 20:20

The flapper valve is usually the problem with intermittent filling. Some times these just don't seat well and the water will cycle on until the tank is full try jiggling the handle to seat the flapper. If it always cycles the flapper probably needs replacing. The toilet cycle has nothing to do with the wax ring , the smell may indicate a leaking wax ring. I prefer the wax rings with a foam core. If the flooring is bad it will need to be repaired, If it is a toilet base that is sitting on uneven tile I find it best to bed the toilet in grout.


The most probable cause of the symptoms you describe is a leaking flush tank.

The bad smell results from sewer gas leaking past the wax ring, which results from the toilet moving when you sit on it, which results from deterioration and rotting of the floor, which results from the floor being constantly just a little bit wet, which results from a small amount of clean water seeping from the tank.

The intermittent cycling of the fill valve results from a slow lowering of the water level in the tank, which results from a small amount of clean water seeping from the tank.

This kind of leak can be very hard to find. Often there is no dripping and you can detect the seepage only by wiping the outside of the bowl and the surrounding floor with paper towels or toilet paper. The leak can even be completely inaccessible, if the ceramic bowl is cracked under the tank seal.

In a case like this, with the moving toilet and the bad smell and all, you will have to remove the toilet to diagnose the problem.

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