Sewer gas smell downstairs after install upstairs

[Kirk Harrod]

Hello Friends! I bought an old house built in 1895. The plumbing was all added later in an addition of 2 floors in the back of the house. The house had been previously owned by jackasses, who appear to have hired jackasses to work on the place.

Anyway, I am trying to fix everything correctly. I recently installed a new toilet upstairs. It works great, flushes well, no sewer gas smell in the upstairs bathroom.

When the upstairs toilet is flushed, downstairs it smells of sewer gas very strongly. The smell seems to be coming from the drain pipes under the kitchen sink that connect to the bathroom sink drain and tub drain. The smell is definitely not coming from either toilet. It did not do this when the old toilet upstairs was still in place.

Does anyone have any idea of why a new toilet install would cause this problem?

The sink and bathroom drains in the downstairs bathroom do not appear to be connected to the vent pipe that the downstairs toilet is connected to. They appear to not be vented.

I have visually inspected the two roof vents for blockage with bird nest or leaves. They were clear. I plan on running a snake down the roof vent.

Thanks in advance for any help!

 

[WJcandee]

One somewhat-educated guess is that your new toilet has a greater rush of water than the old one. The old one probably used more water, but it probably flowed out more slowly. Newer toilets, even gravity ones (but certainly pressure assists), do more with less by having a faster rush of water through the toilet and through the outflow into the closet bend. The faster rush of water will tend to expose defective installations, including back-to-back toilets mounted on a cross, and insufficiently-vented fixtures. In the case of the latter, the rush of water can cause the trap below an unvented sink or shower to siphon (which is the purpose of venting -- preventing siphoning of traps). Once the trap in the sink is siphoned, sewer gas is able to flow up the pipe past the trap. Do you ever hear a gurgling in the tub/bathroom sink/kitchen sink when you flush upstairs?

 

[Sponsor]

 

[Kirk Harrod]

Thank you, that sounds like it is the problem.

 

[Cameron Fields]

Definitely related to the lack of being vented.
Cameron Fields