venting a bathroom sink

[Tom7227]

I have a bathroom sink that has been sluggish since we bought the house. It is on the second floor. As far as I can tell the drain pipe appears to go 90 degrees down inside the wall. The drain is 14 inches from the wall on the left. There is another bathroom butting up against this one but the drain pipe in question is not common with that bathroom. There is no way that the drain in question goes directly down to the basement so at some point it has to go into some sort of horizontal pipe that leads over to the common drain for the sink and toilet from the other room.

I can fairly easily get to the drain pipe in question if I work through a common closet wall that is an interior wall. Assuming I can get to it would I be able to tap into the drain pipe for the sink and run a vent line up 3-6 feet but have it inside an enclosed wall space? It would be much higher than any existing drain so the chance of a back up seems nil. I suppose it would be wise to put in a check valve to make sure.

I know that a diagram would help but I couldn't figure out how to do it. Really the only question is the propriety of a vent pipe in an enclosed wall space. I suppose the possible sewer gas smell might make it a bit unpleasant. Maybe I could do it into a closet where my wife hangs her clothing.

[Eric Wettschreck]

You are correct sir, the sewer gas smell would be pretty horrible.

Is there a way you can tap this drain into another existing/vented drain from the other bathroom, then cap what's left of the "Old" drain? Tough for me to explain but if you can connect the 2 drains it may be a lot easier for you.

[CAMAN]

You would want to install what is called an "air admittance valve" onto the end of the vent pipe. It is a cap with a diaphragm inside that allows air in when there is negative pressure caused by water flow but closes when there is neutral or positive pressure on the line. They aren't always the greatest and sometimes don't work quite properly for one reason or another in a certain situations. I would figure out the easiest way to direct vent it outside or to the main stack before going with one, but they are always an option.

[Redlantern]

How old is the house? In a more current home, say 30-40 years old at most, I would think that what appears to be a ninety turning down is more likely a sanitary tee. You wouldn't be able to see the upper part of the tee from the opening of the trap arm. Of course, this is assuming the plumber followed basic plumbing codes.

Not quite sure what you mean by a chek valve. If you mean putting one in the waste pipe, unless it's accesible, I wouldn't. They fail on occassion and it's nice to be able to get to them easily. I'm not sure if the air admitance valve is legal anymore in Minnesota. I never put them in. They just seem like a mold issue waiting to happen. I think your best bet, if you haven't tried this already, is to run anauger down the pipe and see if you can't get it to drain better. If that doesn't work, it might be neccesary to do some exploratory plumbing and open up some walls to find out what's going on.

[efgh]

We had a slugish drain in the kitchen sink in a house we purchased. On closer inspection the drain pipe was about 4/5 plugged. It was plugged because the people who lived there before always washed their hair in the sink and the loose hair plugged the pipe in a elbow.

[chad austin]

Tom, Did you buy the house new? How old is the house?

[Surface Tension]

First pull the trap, clean it out, snake the line. Very good chance that fixes the slow drain and case closed.

There might or might not be a wye at the wall connection but that doesn't mean its not vented. That vent can be 5' away on a1 1/4 drain.

Smelling sewer gas because the trap is being siphoned would be reason to ad a vent.

The air admittance valve needs to be in an open space. If it went in the wall you'd have to vent the wall.

You need is a minimum of 4" above the trap. That should be able to be done inside the vanity.

I believe you can get the AAV built into the trap as well.

[Tom7227]

House was built in 65 and we are the second owners. Builder put in copper waste pipes so no way to find them using a stud finder. I took it apart and used one of the 18 inch plastic gunk grabbers and got a decent amount out and that has been the history of the cleaning. Get it to the place where it has to be going down under the joists and nothing I use - even a steel snake - will go any further. I will check on the air admittance valve and see if I can work it in under the vanity.

Thanks for the help.

[Redlantern]

Tom, I still think you are going to have trouble with the air admittance valve installed (and not just because it doesn't meet code). Check to make sure that the vent going through the roof isn't plugged. It may or may not be tied in with the vent stack for the water closet. I think though that you are going to have to hire someone to come out and try augering the waste pipe.

[Tom7227]

Eric - everything else works fine and this sink has been sluggish for years. We got central sewer only 5 years ago and I doubt there's anything in those new lines.

[Surface Tension]

"Get it to the place where it has to be going down under the joists and nothing I use - even a steel snake - will go any further. "

That is were you'll have to use an auger.

[Tom7227]

I think maybe I need to buy one of those snake cameras to check it out. A guy can always use a new toy. FF had a Milwaukee rig on display a month or so ago. Actually I have it working pretty well now and so I'm going to let it ride until it plugs up again in a couple years.