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richaloren · Jan 10, 2011, 11:51 PM

We have been in our house just over a year. Every time it gets really cold we get a strong sewer smell in our half bath on the main floor. It seems the vent for the sink seems to crust over with either snow or frost when we get below 5 degrees. I got on the roof a couple of weeks ago and knocked this frost off the top of the vent and the odor went away almost immed. I put an pvc elbow on the pipe to keep snow off, but now it is cold again, snow on the roof so I can't check for a frost plug, and the temp is down and the odor is back. Is there any way to improve air flow through this 2 inch vent pipe. Would lengthening the pipe further above the roof help any? Thanks. ****

joypulv · Jan 11, 2011, 02:00 AM

Even with frost on top of the vent, you shouldn't be getting smells if your sink p trap is filled with water. Maybe it is dry from not being used much. Try running a cup or 2 or water once a week.

massplumber2008 · Jan 11, 2011, 06:42 AM

Hi guys...

Actually, Joypulv, if the sink vent frosted over then the sink is VENTLESS and when the sink drains it will glug/chug in such a way that it can/will siphon out the PTRAP and can allow sewer gasses to enter the home.

Further, if the toilet and tub are WET VENTED through the sink drain/vent then you would definitely have sewer gasses escape as the toilet tries to draw air into the system every time the toilet flushes or the tub drains and will usually pull air through the sink drain again allowing sewer gasses into the house... ;)

Richaloren... how far above the roof is the vent now? Does this vent get buried periodically or just frost over occasionally? Let me know, please.

Finally, I'm thinking it may be a good idea to increase the vent size to 3"...even 4" at least ABOVE THE ROOF LINE... maybe.

Answer my questions, OK?

Mark

richaloren · Jan 11, 2011, 03:18 PM

The sink if vented underneath with a "Studor" mini vent. I think the sink and toilet are vented seperatly. The problem only occurs when it is very cold outside. Was suggested that the cold air was pushing down air in the vent. Not sure about that. The vent never has been covered with snow. It sticks up about a foot and a half above the roof surface. Thanks for your response.

massplumber2008 · Jan 11, 2011, 04:55 PM

What does, "The sink if vented underneath with a "Studor" mini vent" mean... please elaborate.

I doubt air is pushing down, but I suppose it could contribute a bit, for sure. I'm still betting on the fact that the 2" is a pipe size we have seen cover/ice over, so, in my opinion, when you can do it safely, I'd increase the size of the vent to a 3" pipe and extend it up pretty high... say 24-30" Here, just cut the pipe low and install a 3"x2" reducing coupling... that may help here.

Let me know more if you want...

Mark

richaloren · Jan 11, 2011, 05:24 PM

The under sink vent is plumbed into the sink drain, I believe so when water is run in the sink it is so it will drain smoothly without chugging. I will try the taller, larger vent when possible. Thanks

massplumber2008 · Jan 11, 2011, 05:36 PM

If the vent is under the sink and you are having issues with odor then change out the AAV first... see if that improves things, OK? Super easy job... just spins out and spins back in.

Mark

richaloren · Jan 11, 2011, 07:09 PM

We have done that last year with a brand new vent replacement and had no positive results.

massplumber2008 · Jan 11, 2011, 07:28 PM

OK, got you!

Have you removed the pop-up (stopper) and cleaned it and the 6-18" or so until the sink Ptrap? May want to try that. Here (see image below), you remove the retaining nut so that you can move the horizontal pivot rod back and out of the stopper and then remove the stopper and clean the stopper itself as well as cleaning the insides of the pipe to the ptrap. If needed, you can clean the interior pipe with a coat hanger and a small rag... just be careful not to lose the rag... ;)

Otherwise I can't offer much more but I would suggest that you pop back between now and the time you increase the vent pipe size and see what the other members think about this issue. Over time, we can get some great options to consider...

Pop back and please keep us posted as we all enjoy hearing how something like this turns out, OK?

Thanks...

Mark

richaloren · Jan 12, 2011, 03:28 PM

Mark, warmed up today to 25 degrees, Got on roof, vent had partial icing over, but mostely open. Odor gone in house. Got 3" vent on old 2" vent, about 2 ft. higher. For some reason that vent seems to ice up, others are OK,

massplumber2008 · Jan 12, 2011, 03:35 PM

Sometimes the way the house faces will predispose a certain vent to icing over. Increasing the vent size should help.

Good luck!

Mark