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Issue:

When the weather and pressure changes, my bathroom will smell terrible and the sink has trouble draining. Sometimes the sink won't drain until the pressure changes again.

Attempts:

Changed Toilet Flange, this resolved some occurrences of the smell. Refit and sealed the sink's drain into the wall, this added no benefits.

Best Guess:

Seems that the pressure change pushes down on the ventilation forcing gases to seek the path of least resistance, out the toilet but it also pushes back enough to prevent proper drainage on the sink.

I doubt changing or adding to the Toilet Flange is going to solve all my problems, but perhaps a thicker one would at least help with the smell more...

Unfortunately, even after all my research on this problem, I'm not sure what to try next because I honestly don't know for certain what the problem is.

Void Serpent
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1 Answers1

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This sounds like the classic description of a blocked vent stack.

Somewhere between your traps and the sewer there is -- or should be -- a connection that is open to the outside air. Because fetid smells may come out of this pipe, the opening is usually placed above the roof, or at least far from where anybody might be.

If this vent becomes blocked, air pressure in the sewer line may force gases past one of the traps into your house. Or, flushing the toilet may create a partial vacuum in the sewer line that will suck the water out of a trap leaving it useless.

In your case, normal weather-related atmospheric pressure changes are driving gases back and forth through one or more of your drain traps. Check the venting of your drain lines.

A. I. Breveleri
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  • I've been on the roof and couldn't find anything obvious in either of the two stacks (one above the kitchen, one above the bathroom) from that vantage point anyway. I assume it's possible for the blockage to be more internal on the vent and not readily visible? – Void Serpent Apr 05 '17 at 13:01
  • It sounds like the blockage is most likely at the junction of the vent and the drain. The effect of partial or complete blockages is very dependent on the particular geometry of your plumbing, so it's hard to know what to try without seeing the actual pipes. - You could hire a service to root out all your drains, or you might need to send a long snake down the vent pipe. – A. I. Breveleri Apr 05 '17 at 13:26