Smoke test - smoke coming out of the bowl

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grady

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I've been investigating a sewer gas smell in my shop for several years. The smell starts in fall when temps will drop below 40, not necessarily freezing. Checked vent pipes, checked drains, changed toilet seal, etc.. to no avail. Really started thinking it was a vent pipe connection drying out with the lower humidity or some sort of drain siphoning from negative pressure. Finally did a crude smoke test this morning. Removed p trap, smoke bomb in shop vac connected to a sink drain. Immediately noticed smoke coming out of toilet bowl right under the lip where the water enters up flushing.

My guess is that it is bad toilet casting and the smoke filtered through that smaller hole that is a remnant of how the toilet was cast. If smoke can make it through here, surely sewer gas can. I don't know how else smoke could have made it through to the bowl, even if the wax seal was bad. So, is it a bad toilet casting that only acts up when the barometric pressure rises as temps drop and the sewer gas is looking for an easier route out than the roof vent? Could I just caulk this small hole or better to buy a new toilet? For now, I've got the toilet off, drain hole plugged and sealed up so we'll see if the smell returns after it gets cold again at night. Thanks for any insight.
 

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Chucky_ott

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Changes in temperature could increase the stack effect in different areas of your house but I don't see how that would suck in air through the toilet.
Are you running a flued furnace or fireplace when the temperature drops? Both of those will exhaust warm air through the chimney (stack effect here too). That air needs to be replaced somehow. Usually, you would have an air vent close to the furnace to allow outside air in. If you don't, and using the furnace/fireplace creates a negative pressure in the house, air will be sucked in from elsewhere....gaps around doors and windows, holes in walls, etc. If that toilet is defective, then air could be sucked in through the vent. I've never seen a hole in a toilet like that...but then again, I'm not a plumber.
 

Sylvan

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First and foremost, go get yourself checked out as I had a case where an accountant was renting an office space and after a few months he had severe headaches and suffered from respiratory illness.

The culprit was sewer fumes(gases) coming up under the toilet.

Heat rises and the sewers are normally warmer than an unheated space.

Also, if you use a space heater without enough free air for proper combustion it can suck air from any place available including sucking a trap dry (negative pressure)

Sewer gases​

Sewer gases may include hydrogen sulfide, ammonia, methane, esters, carbon monoxide, sulfur dioxide and nitrogen oxides. Improper disposal of petroleum products ...



 

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