We have a 2 story home with a bathroom that has a shower and toilet upstairs. The upstairs bathroom is not used very much or sporadically at best. Every 3-4 months the water in the toilet will disappear and the whole upstairs will fill with a very foul odor. (The tank still has water in it.) When this occurs even flushing the toilet every few hours doesn't seem to help. This has occurred since we put the house up 18 years ago, back then it only occurred in the spring and fall, now it occurs about 4 times a year. I'd really appreciate any help figuring out why the bowl doesn't hold water itermittently and why it fills the upstairs with the foul odor. Since our daughters have grown and moved out we use the upstairs for quests and return visits.

Thank you!

Since that soil line is not used much and the toilet bowl water evaporates and allows sewer gas and more fresh air to get into the line to help create more bacteria lets try this to kill it and go from there. Flush toilet and get a full bowel Pour a good amount of bleach in about 50% and let it sit for an hour or two now flush bowl to help kill bacteria in soil line. Do this with the tub and sink also. Fill them up and bleach let set and let the drains run at full tilt. One other area for smell is the waste and overflow in the sink and tub. As opposed to stuffing a rag in the drain trap fill up the sink with 1/2 water and 1/2 bleach and let it go into the overflow in the sink. Fill the tub with a half a gallon of bleach and water now scoop that out and pour that in the overflow. See what that does and if that doesn't work get back.

Signed 21 Boat

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What you're smelling is probably the methane seeping it's way back up because the water in the trap has evaporated... like 21boat said.

Hi all...

Earleybird:

As mentioned, sounds like you are letting the toilet dry out over time... this results in sewer gasses entering into the home and that can be an awful smell as you have experienced... never mind unhealthy as well.

In the future, be sure to flush the toilet at least once per month. You also need to use the sink and the tub/shower as these fixtures also have traps that can dry out and create same issue with odors.

In fact, it is not good to leave faucets or parts in toilet sitting too long without using them. Here, seals dry out, parts get stuck and this increases the chances that parts will fail and cause issues far earlier than if you used the plumbing regularly.

Have good day...

MARK