terrible smell of sewer gas in bathroom

[suzannehome]

I moved into a townhouse about a year ago, and several months ago I began to notice the smell of sewer gas in my main floor half bath. Since that time the smell had gotten much worse and it is to the point that I haven't been able to use that bathroom for several months. We initially thought it was coming from the toilet so we replaced the toilet seals into the floor. Then we came to think the smell was coming from the sick--we checked the trap and it has water, we checked to see if there was leakage from any pipes under the sink and nothing was found, we resealed the connections going to and from the trap. Nothing helped. Last week we removed part of the wall behind the sink pipes to see if the smell was coming from a hole in the pipes behind the wall, but there is no smell in the wall. Oddly, a couple of months ago when I filled the sink w/ water, some water came from behind the wall under the floor molding under the sink. I was able to reproduce that effect once but not since that time. I don't know if that is related. There are 2 full baths upstairs which don't seem to have a problem though I sometimes smell a similar-type odor coming from the toilet of one bathroom. Please help! It is really unbearable in that downstairs bathroom. Thanks!

Suzanne Smolkin

[LazyPup]

You didnt mention how old the structure is or what type of pipes you have in the wall.

If it is an older building with cast iron soil pipes, the small diameter lateral waste arms are most likely made out of threaded iron pipe or brass pipe.

There are two common sources of leaks in that type of system. The treaded part of the iron pipes tend to rust through at the joints or the underside of brass pipes will corrode through the pipe wall. Both scenarios will produce leaks in the drainage system.

The preferred method to solve the problem is to remove the old iron pipe or brass pipe and replace with PVC.

Also, check to see if there happens to be a defective wax ring under the toilets on the second floor. Sewer gasses are basically heavier than air and once they get into the floor or wall cavities they will settle to the lowest point before becoming noticable.

There is another possibility, although very rare. Sometimes people make the mistake of terminating a vent in the attic space instead of taking it on out through the roof as it should be. The gasses release in the attic space and settle down through the plumbing chase to the lower floors.

[dcsnowden]

Suzanne I had a similar problem in one of our townhomes. Now in my case the renter also described a sewer smell, but when I got there it was more of a rotting smell. If your downstairs 1/2 bath has an exhaust vent, check for odors there, turns out ours was a dead rodent lying right next to the fan in the cieling. If it truly is a sewer type smell, then LazyPup's asessment is more than likely correct and PVC is the only way to go.

[Hube]

dcsnowden; A rodent rotting will give off an odor for a few days,etc
However, a Sewer smell , UNLESS CORRECTED, will always give off an ODOR.[:I]

[mrcaptainbob]

"Oddly, a couple of months ago when I filled the sink w/ water, some water came from behind the wall under the floor molding under the sink. I was able to reproduce that effect once but not since that time. I don't know if that is related. "
How deep did you fill that sink? Was it to the overflow port? Or did it start to leak when you opened the drain?
There could be a leak in the drain pipe in the wall that may not appear with normal use. Upon filling the sink and opening the drain, there's a heavier flush to the water, and though there's no real 'pressure' to that flow, there's a bit more pressure to the inside walls that may manifest itself through a hole or cracked seam. If it's all PVC, then there may have been a hole drilled for some hanging device. (picture hook or maybe a tool hook)...interesting that it came from under the molding, though. I'd put a hole in the wall in that area and start using a flashlight and small mirror to scan the inside for more clues.....

[LazyPup]

Air inlet valves (Studor vents) are another common source of sewer gas odors that I commonly forget to look for. Why? Because where i took my training they were prohibited by the code, and since moving to this region where they are commonly used, I often forget to look for them.

In those jurisdictions where air inlet valves are permitted there are very strict regulations regarding when and how they are to be used but since I moved to this region three years ago I am rapidly finding they are often used by Homeowners, DIY'ers and wanna be contractors with little to no regard for the proper application as outlined in the local codes.

By code, when permitted, air inlet valves must be located a minimum of 6 inches above the highest flood level rim of the fixture they serve, and must be in a non-concealed location to permit servicing. In some instances, and with approval of the local inspection authority an air inlet valve may be attached on a waste riser under the sink, if the valve is a minimum of 4 inches above the sanitary tee that serves the sink trap.

In reality they are often being used under the sink in an upper part of the cabinetry or in some instances attached to a tee and short stub up on pipes in the basement ceilings. I have even found then inside the walls, especially on tub drains.

Air inlet valves are commonly used under the kitchen sink when the sink is installed on an island where it is impossible to run a vent up to the roof.

The preferred method of venting an island sink is to install an island loop vent.

An air inlet valve will appear like a small cap with side slots on the top of a section of waste pipe.

In normal operation the air inlet valve has a rubber flapper that is held in the closed position by a spring. Whenever their is a negative pressure in a drain pipe the ambient air pressure pushes the flapper down allowing air into the pipe in the same manner as a proper vent pipe would do. Once the air pressure in the pipe is equalized the spring again closes the flapper. However, often the flappers will stick in the open position and allow sewer gases to enter the home.

Air inlet valves are screwed into a thread adapter on the end of the pipe, and if they are defective you simply unscrew and replace them.

[Hube]

Mrcaptainbob has maybe jogged my memory on a problem we had many years ago...
We had a "odd smell" that we mistook for sewer gas, but it turned out to be some crud,etc that was accumulating in the overflow part of the basin. We cleaned it with a bleach /water solution and from there on it was fine. No more odor. Of course we made sure we never overfilled the basin too much anymore ,thus avoiding this problem from happening again.
This may not be your problem, but it would be worth looking into. Hube

[suzannehome]

quote:Originally posted by mrcaptainbob

"Oddly, a couple of months ago when I filled the sink w/ water, some water came from behind the wall under the floor molding under the sink. I was able to reproduce that effect once but not since that time. I don't know if that is related. "
How deep did you fill that sink? Was it to the overflow port? Or did it start to leak when you opened the drain?
There could be a leak in the drain pipe in the wall that may not appear with normal use. Upon filling the sink and opening the drain, there's a heavier flush to the water, and though there's no real 'pressure' to that flow, there's a bit more pressure to the inside walls that may manifest itself through a hole or cracked seam. If it's all PVC, then there may have been a hole drilled for some hanging device. (picture hook or maybe a tool hook)...interesting that it came from under the molding, though. I'd put a hole in the wall in that area and start using a flashlight and small mirror to scan the inside for more clues.....

Suzanne Smolkin

[suzannehome]

quote:Originally posted by suzannehome

Suzanne Smolkin

Suzanne Smolkin

[suzannehome]

First let me apologize for the last 2 messages. I was having some computer problems. Thanks so much for all of the advice! To answer some questions, my townhouse was built in 1987 and the pipes seem to be PVC. We did replace the wax rings under the toilet but unfortunately that did not help at all. When I filled the sink with water, it was actually a combination of water and vinegar, and I filled it beyond the overflow port in case there was "bad stuff" in the port. Thinking back, I believe that the leak from behind the wall only came once I opened the drain. I am wondering if the problem could be from a nail or screw in a pipe behind the bathroom wall, given that the area behind the wall does not seem to smell (from the hole we made on the other side)? We just made 2 more holes in the bathroom wall below a mirror that seemed to have been installed just prior to my buying the house. Since doing that the smell seems to have gotten significanly worse and in addition, the odor now seems to be coming up strongly from one of the upstairs toilets when the seat is opened. Any thoughts?

Suzanne Smolkin