|Posted by More on April 26, 2002 at 20:44:42:|
|In response to Re: sewer gases|
In order for you to get sewer gas odor rising from the gravity sewer to come into the bathroom through the sink drains, rather than the gas and odor rising all the way to the roof vent, you need one or more of three things to happen. First the u traps ( P traps) under the sinks must be constructed in such a way that even though they hold water, they allow gas and odor to pass also - that is something you or your plumber can check by stopping off the roof vent, adding plumber's smoke to the lower floor drains (or a cleanout) and observing if the smoke enters the upstairs room from lavatory (or shower) drain.
Second the roof vent needs to be obstructed from free venting, either by having more than ninety degrees bend in the updraft, or restricted updraft flow from obstructions in the vent such as a bird or squirrel nest, (or as sometimes happens, roofing paper wad [or scrap of roofing material} stuffed in the vent by roofers).
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