Toilet Water Gets Gone

[Plugdup]

This has been going on for 35 years. Sure I’ve lived with it but would like to solve it.

Got 2 toilets not back to back - maybe 20’ apart on a straight line. Both vented to a common vent system; there is ony one pipe through the roof. One of them looses water such that the internal trap gets emptied or at least partially emptied letting fumes into the house. This does not happen all the time. It can be years between events and an event might continue for up to several months. Just some times and the rate of loss varies. Only the one toilet and not the other; never the other.

First reaction will be that it leaks; but! When away for vacation I would remove the toilet from the pipe, stand it in the shower, cover the bowl with plastic wrap so the water could not evaporate and after 2 weeks the water had not drained. Not a fraction.

My only thought is that the wind over the vent pipe opening creates low pressure thereby sucking the water out of that toilet. But why not both toilets? And if that is so why would it continue to suck water out after the trap is partly emptied? Probably wouldn’t. I suppose it might suck out just enough that the trap is ineffective but still has some water in it. Not only that it happens with or w/o wind. Scratch that theory.

Sewer fumes have gotten into the house but maybe less than would be if the trap was fully emptied. The fumes have been smelled for sure. I have not swapped the toilets nor tried a different one.

I cannot relate this to wind or heat or cold or temperature or weather or time of year.

 

[Reach4]

I cannot relate this to wind or heat or cold or temperature or weather or time of year.

Can you relate it to how often you flush the other toilet?

 

[Sponsor]

 

[Plugdup]

Can you relate it to how often you flush the other toilet?

Never thought of that but doubt it as the other does not get flushed excessively and it will empty out when we are away and neither are being used. I will, however, try to look at that.

 

[Reach4]

Never thought of that but doubt it as the other does not get flushed excessively and it will empty out when we are away and neither are being used. I will, however, try to look at that.

If the toilet empties when you are gone, you can probably not bother with that.

 

[JRC3]

I would suspect bad venting more than anything or excessive wind...But...

Back around 1990 when I was like 20, I installed a toilet on a remodel that kept leaking under the toilet onto the new tile. I reset it with new wax rings several times and as a last resort I went old school and even used plumbers putty with the same results. Decide to take the toilet and sit it on blocks and fill it up and let it sit. Turns out the entrance to the trap hadn't been glazed properly and water was seeping through into skirt area.

I could see this happening on a slab and maybe never seeing any water on the floor. Or even running down a stack pipe into a crawlspace or basement into the soil below.

 

[Plugdup]

I remember back around 1990 when I was 55....
Well I've been under that house (crawlspace) a lot of times and hadn't seen any water or wet wood etc but I will check that out next day or two. Actually that pipe is right next to the crawl hole. Also:

I wonder if there could be a crack that would leak only if the toilet is bolted down; not if it was free standing in the shower as I described above. Seems a bit much as those hold down bolts don’t get torqued all that much. Only way to prove that would be another unit.