Off Topic--Problem With Drain Vent On Lavatory Sink

[npalen]

Our home was built by a Vocational-Technical school class back in '74. I suspect that they forgot to vent the drain in one of the bathrooms as I get the sewer smell when draining the sink. The trap is in place so I'm guessing the only way it can vent is back up thru the sink drain. Anyone have suggestions as to how this might be remedied without tearing into the wall? (You may wonder why I haven't fixed this after 40 years Thank you in advance.

 

[boggen]

make a longer P trap. further it goes down and then comes back up same distance. the more pressure gasses / air will need to come back through the sink. ((most likely will not fully work if "siphon / suction" gets strong enough to pull water out of the P trap)) have seen some pretty ugly P traps at local hardware stores. that i could hardly call a P trap.

most likely not to code. run 1/2" or so hose and tee into drain just after P trap. so the Tee is pointing up. run the 1/2" or so hose up through ceiling and tie it into the drain vent stack in attic.

you might try enlarging pipe at or just after P trap. to point it connects to a vent. so waste water drains in lower portion of pipe and air can flow in upper half of the pipe.

=========
with above without proper venting. anything above more likely crud shot at best.

did someone leave a poo a tad to big and plug up vent for sink? *blames kids trying to flush stuff down toilet*

 

[ozley]

Our home was built by a Vocational-Technical school class back in '74. I suspect that they forgot to vent the drain in one of the bathrooms as I get the sewer smell when draining the sink. The trap is in place so I'm guessing the only way it can vent is back up thru the sink drain. Anyone have suggestions as to how this might be remedied without tearing into the wall? (You may wonder why I haven't fixed this after 40 years Thank you in advance.

If you can see the venting in the attic you may fine the pipe has a belly in it which can fill with water from condensation or rain blocking the vent.

 

[npalen]

Thanks for the feedback. guys. I'll check the venting in the attic also. Any and all suggestions appreciated.

 

[soilsailor]

If the house has a vent, which it sounds like it does, then I believe you may be able to add an air admittance valve. Note: I am not a plumber nor did I sleep at a Holiday Inn last night. Just watched lots of videos on You Tube.

 

[farmer2009]

You can add a valve under the sink. I don't know the name of it but it was designed for use in islands with a sink. Don't want the vent pipe running to ceiling. But you tee it in on sewer side of trap and run it as high under the cabinet as possible.

 

[MossRoad]

Funny I was just dealing with this today. You should check out an AAV, Air Admittance Valve.

I'm buying one tomorrow.

Shop Keeney Mfg. Co. 1-1/2-in Plastic Mini Air Admittance Vent at Lowes.com

 

[kenmac]

If it's been draining water and you have had no problems from 74 until now.. I doubt it's a vent problem..

Soap scum & hair will gather in the drain lines over the yrs and tend to smell just like sewage..
Take your trap apart and inspect the drain pipe

 

[npalen]

OP here. I hate to admit it but I've been putting up with it for longer than I can remember. I did clean the trap recently so I don't think that is the problem.
Thanks for the link to the air admittance valve. May have to give that a try.

 

[kenmac]

If that's what the problem is. I would use/recommend studor vent brand AAV..I have use a number of these without any issues

 

[cat fever]

Questions;

Has it always stunk like sewer, or did this come on gradually over the years? When you first enter the bathroom does it smell? You said earlier in this thread you pulled the trap apart to clean it. When you took it apart was the U bend full of water? Kenmac was starting to hit the nail on the head in his post.

I'll tell you this, you could vent the whole house no problem with a 3/4" pipe. So the vent is not the problem. A vent prevents a siphon on the p trap, nothing else. So if it only stinks when draining, the vent is not the problem because the trap is always full. Here's what I would try, pour some drain cleaner in the overflow holes of the wash basin. What happens is over the years scum builds up in the drain waste line. (the part mounted to the basin itself) It continues to build/plug the overflow holes and the gasket itself will get pretty stinky along with the old dried out putty. So putting some good drain cleaner down the overflow will clear out the section I'm talking about. It never hurts to plug the drain and fill the basin to the point it overflows into the "overflow" just to keep it clean and washed out. A common problem with most drains and people is they get done washing and instantly turn of the water, not allowing any time to wash the dirt/soap/toothpaste/spit etc down the drain.

Been a Master Plumber for almost 30 years now. I could be wrong but I doubt it.

 

[cat fever]

If it's been draining water and you have had no problems from 74 until now.. I doubt it's a vent problem..

Soap scum & hair will gather in the drain lines over the yrs and tend to smell just like sewage..
Take your trap apart and inspect the drain pipe

I just read your profile, when I read your post I thought "he knows what he's talking about". Now I know why.:thumbsup:

When I went through plumbing school (1985ish) auto vents were not legal, although I see them used much more now I'm still not a fan.

 

[kenmac]

I just read your profile, when I read your post I thought "he knows what he's talking about". Now I know why.:thumbsup:

When I went through plumbing school (1985ish) auto vents were not legal, although I see them used much more now I'm still not a fan.

We don't use them on a regular basis, but sometimes you have to do what you have to do.

 

[npalen]

The ONLY time that I smell the gas is when draining water out of the sink. This has been going on for as long as I can remember but can't say positively that it dates back to 1974. I've been putting up with it as I'm usually the only one of the family that uses this sink.
I should have clarified when saying I "cleaned the trap" that it was only using drain cleaner. (unplugger) May have to take the trap apart and see what kind of life forms may be hiding in there.

 

[kenmac]

That's why I don't think you have a vent issue..I'm not there to be able to inspect.. This is only my opinion

 

[ozley]

That's why I don't think you have a vent issue..I'm not there to be able to inspect.. This is only my opinion

That has my vote too.

 

[cat fever]

That's why I don't think you have a vent issue..I'm not there to be able to inspect.. This is only my opinion

So you now have kenmac, ozley and myself saying it's not a venting issue. I would try what I suggested above. Be careful and be creative, you'll need a flexible funnel to get the drain cleaner in the "overflow" hole. After the drain cleaner has had several minutes to work flush out the overflow good with cold water.
In case you are keeping score--that's 3 plumber's by schooling / profession.

 

[Citydude]

If that's what the problem is. I would use/recommend studor vent brand AAV..I have use a number of these without any issues

This^^^^.

 

[cat fever]

The ONLY time that I smell the gas is when draining water out of the sink. This has been going on for as long as I can remember but can't say positively that it dates back to 1974. I've been putting up with it as I'm usually the only one of the family that uses this sink.
I should have clarified when saying I "cleaned the trap" that it was only using drain cleaner. (unplugger) May have to take the trap apart and see what kind of life forms may be hiding in there.

Knowing if water is in the P-trap is the key. You stated above "The ONLY time that I smell the gas is when draining water out of the sink". So I would guess the trap is staying full meaning for sure the vent is not the issue. If you were to take apart the drain on the bottom of the basin (not saying to do this) and see what's in there you would understand why I'm just saying to pour drain cleaner in the overflow hole. Just out of curiosity is the washbasin China, Cast Iron, plastic or porcelain over steel?

 

[Citydude]

While building a bathroom in my basement the inspector that did the inspection was a plumber before he became an inspector. He advised me to put a studer vent in the drain line under the sink. I explained that the p trap wouldn't go dry as we expected to use the sink. He said the sink was too far from the vent pipe and it wouldn't properly vent so the the sewer gas would work its way up through the p trap while running the water. I'm no plumber, but there hasn't been any smelly gas from the sink when we use it. I think the vent cost me $15 at Home Depot.