We’re 98% complete our whole home reno (moved in) and the main floor powder room vanity sink is giving off a foul gas, mainly when it is used through the overflow. All plumbing and fixtures are new.
Plumbing is pretty standard:
– sink is a Kohler Archer which drains via chrome U Trap into the ABS once it passes into the wall. 20″ above the sink level is a cheater vent on the ABS drain stack.
The odour is worst when you use the sink and you can actually smell it coming from the overflow (sink).
– I can’t figure out how any sewer gas could be getting past the U Trap?
– Even if the cheater vent was faulty (stuck open) the smell would come from the wall and not the overflow?
– The only thing I can think is the sink has something decaying in the the actual overflow gap.
Any thoughts? I’m stumped!
Replies
Basically, there is a bunch of bacteria farting. Take some thick toilet bowl cleaner and squirt it into the overflow, let sit and then rinse with hot water.
Came up with the same idea as a few of you - treat the overflow with some sort of bug bomb and flush. I'll give it a go and see how it turns out.With regards to the rest of the plumbing, there was a powder room (vanity and toilet) prior to but all the stacks and under floor pipes are new (clay to PVC and ABS).Vanity stack goes into the floor joist, across at good slope, and ties into the toilet stack which then goes straight down into the basement slab and ties into the main waste pipes.Thanks for the replies. Sanity has temporarily returned!Van G
Being a new sink install, that is not likely
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This does not pass the smell test? If the order is truly coming from the
overflow and not some near by pass it almost has to be in the overflow.While not likely I wonder if it is possible that a mouse or something got into it when it was in storage?.
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OK, that is an option that hadn't occurred to me. I know my one plumber gets very particular about the order of things re venting, sometimes changing what I think is the path, so I can imagine a DIY HO making a goof in venting and siphning that trap dry due to excess pressure changes in the system.
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Well you do bring up something that I had not thought of. The trap being sucked dry between usages.I was thinking more of a leaking in the venting that allow the smell out. And in that case it would be more generalized and not specifically at the overflow.Ain't detective work fun!Truly, but often it can also be very frustrating..
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Edited 4/6/2009 9:41 am by BillHartmann
"Ain't detective work fun!"Amen - a great game of logic, chess, Clue, and partying all rolled into one here.
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Can't smell it from here....
but, it's not a good idea to use toilet bowl cleaner in your new sink.
The product is extremely caustic and the finish in the sink, should there be spills, cannot stand up to that abuse. The sink will look like it's 30 years old in a heartbeat.
Any other drains in that bathroom? If, for example, you haven't been using the tub for a while, the water in that trap may have evaporated, allowing those gases into the room.
>>Take some thick toilet bowl cleaner and squirt it into the overflow, let sit and then rinse with hot water.BUT DON"T LET THE CLEANER GET/SIT ON THE PORCELAIN -- the acids in the cleaner will etch it and ruin the finish.(No need to say how I know that <G>)
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I had a similar buildup of sludge/scum/disgusting stuff. You can pull the stopper/pop-up and stuff a plastic grocery bag in ( making sure it wont go down) then pour either toilet cleaner or bleach in and let sit. I used a small hose that hooked to the faucet and hosed it down after pulling the "plug". Another lower risk solution is to close the pop-up and slowly run bowl full of hot water and some soap letting it slowly drain through the offending orifice.
hot water and some soap letting it slowly drain through the offending orifice
Sorry but thats just not right, couldn't resist No one should regard themselve as "God's gift to man." But rather a mere man whos gifts are from God.
van,
You mention that all the fixtures are new, so funk in them doesn't seem probable.
You also mention whole house reno. What did you do in the whole house. Change any plumbing layout? Was the plumbing not vented in that half bath b/4?
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I read right over the new fixture part. I would guess a failed in the closed mode air admittance valve (cheater vent) could cause the trap to siphon and allow sewer gas but should be noticable at drain as well as overflow unless pop-up is closed.
Cheater vent stuck closed was my first thought too. OP, I hope you kept access to it.
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Edited 4/13/2009 12:24 am by Ted W.
I've got a very similar situation in one bathroom. There's no smell until you turn the faucet on and then you get a wave of sewer gas that seems to come from the overflow.
Pretty sure the case here (at my house) is that there's no separate vent for the sink and it's beyond the allowable 5' for that to be the case. Might also be a drainpipe pitched too steeply.
Check your studor vent before you try cleaning out the overflow.
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I am suspecting that there is something in the way you ran your waste and vent stacking that allows the main toilet drain vent through the sink - a distance or location of tie in that creates lower pressure from sink than from main stack out. So it is drawing the methane that direction.
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If you try cleaning out the overflow passage (not a likely source on a new sink), and some of the other suggestions that have been offered, you may still get the offending smell. If so, I have seen cases where the real problem was the water heater giving off hydrogen sulfide, which mimics sewer gas, but has more of a rotten egg odor to it.
It happens when a colony of bacteria builds up in the water heater during periods of non-use--like when the house is empty, waiting to be finished. The bacteria give off the hydrogen sulfide as a by-product of their life cycle.
In the cases I've seen, the place where the odor is noticed is at the master bath sink, because this is first fixture in the house to get used after a night of build-up of the hydrogen sulfide gas.
The smell was not there when you go to the sink, but as soon as you run water, there's the smell, even if you've already closed the pop-up. So, you assume the smell must be from the overflow. Most of us would never suspect the water itself.
The fix is to give the water heater a a shock treatment of chlorine, but don't leave the chlorine concentration too long in the water heater or the system. Flush everything out after about 30 minutes.
The bacteria can re-establish itself after awhile, and you may have to do it again. In persistent cases, it helps to change out the anode rod of the water heater, because some anode rods are made of magnesium, which supports the chemistry leading to the hydrogen sulfide gas. You can change to an aluminum anode rod, if needed.
Good point - some houses here with high magnesium and iron in the water get that smell and need filtration system to help control it. And it is really strange in that it does often only present itself at certain sinks and not other locations in the house.I missed that clue about "when the water is turned on"
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redesigns, you said, "I have seen cases where the real problem was the water heater giving off hydrogen sulfide, which mimics sewer gas, but has more of a rotten egg odor to it. It happens when a colony of bacteria builds up in the water heater during periods of non-use--like when the house is empty, waiting to be finished. The smell was not there when you go to the sink, but as soon as you run water, there's the smell."I hate to hijack the thread, but this "rotten egg" odor (definitely not sewer gas) started (as far as I remember) after I put in a new lav faucet and Electric HWH. Doesn't happen all the time, nor anywhere else in the house. I thought the faucet was out-gassing. The HWH never was dormant during a remodel.Any ideas?
The water heater would not necessarily have to be dormant for a long time, it's just more likely that it can happen under those circumstances.
You'll need to think of some ways of testing to isolate the source. If there's no smell until you open the hot--not the cold with it, just the hot--then it could hardly be anything but the water heater. If the smell is definitely sulfurous (rotten egg), then the water heater is almost certainly growing a colony of bacteria.
A more conclusive test would be to shut off the supply water to the water heater and then disconnect the hot side, or outlet, of the water heater. If the odor is there, you've found it. Don't disconnect the cold side for this test, or blow off a little water from the relief valve. The gas, if there is any, will collect in the top of tank, which is where the hot water connection is made. (The cold side has a dip tube that directs the inflow of water to the bottom of the tank.)
On the other hand, if the odor is there even when no hot water has been run, you'll have to look elsewhere, but in my experience, people often blame smells on sewer gas when it turns out to be something else, like dead birds or mice tucked away someplace where they were trapped during construction. A natural gas or propane leak has sometimes been mistakenly identified as "sewer gas".
To eliminate the possibility of the sewer and vent system, use the peppermint oil/depressurization test that I have detailed in past posts.
Good luck, and let us know what you find.
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