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CuthbertRumbold
Jul 25, 2009, 06:17 PM
Hi Plumbing Experts,
Sorry this is pretty long, but I wanted to include as much detail as I could.

I have a problem with (what I'm pretty sure is) a sewer gas odor coming from the 2 sinks in my home. As far as I can tell the smell only occurs when the water is running.

Sink #1 is a bathroom vanity, 2nd floor, fairly old fixture. It has an S-trap then the 1-1/4" drain goes down through the floor, turns to horizontal and empties into the closet bend of the toilet. The toilet drains directly into the main 3" (cast iron) vertical stack, which continues up and out through the roof.

I've gone up to the roof to check the 3" vent. It's clear of any obstructions.
The sink drains pretty freely so I don't suspect a clog, although there is a gurgle sound.

I've looked for signs that the S trap is being siphoned (looking down into the drain with a flashlight), but I can see none. Flushing the toilet produces barely a ripple, and no odor. The odor only appears when running water in the sink.

Sink #2 is the kitchen sink, 1st floor, and the odor here seems less strong, but still present on occasion. This is a single sink and it's pretty new (as is all the associated plumbing). There's no disposal, but there is a connection for the dishwasher on the tailpiece (the dishwasher drain has a high loop; no air gap). The sink trap is a P-trap and it is vented. The trap arm is 1-1/2" and tees into a 2" PVC line, which joins a horizontal 3" main line in the basement. The vent line is 1-1/2" and joins with a 2" vent in the attic.

Again with this sink the trap doesn't seem to be getting siphoned. If I flush a toilet elsewhere in the house, or drain the washing machine, there's only a ripple in the water in the trap. And no odor. I think the vents are OK. But if you run the water in this sink you will occasionally get a whiff of odor here too.


Is there some way that a 'bubble' of gas can come up through the (P or S) trap while water is flowing down? This seems to be what's happening.


It occurred to me that the smell might be the water itself, but I don't think so. If I pour a glass of water and take it away from the sink for a sniff there's no apparent odor.

Any ideas? I'm flummoxed.

Thanks!
Roy

speedball1
Jul 26, 2009, 05:59 AM
ink #1 is a bathroom vanity, 2nd floor, fairly old fixture. It has an S-trap then the 1-1/4" drain goes down through the floor, turns to horizontal and empties into the closet bend of the toilet. The toilet drains directly into the main 3" (cast iron) vertical stack, which continues up and out through the roof.
Most bad smells from a lavatory come from hair built up on the plunger rod and decaying down there. Every time you open the stopper to drain the lavatory you get a nose full of stinky.
The first thing I would look at is the stopper. Pull it and you will find a rod about 6" down in the drain. Shine a light down there and if you see a buildup of hair fish it out. If the stopper's tied down let me tell you how to free it up. Push down on the plumger so that the stopper pops up. Underneath the lavatory ahead of the clip you will see a knurled nut,(Leave the clip on)Now back the nut out until it's free but don't pull it all the way out. Now while you are pulling up on the stopper GENTLY pull the rod back until the stopper clears, stop! Now screw the nut back in place and just snug it up with a pair of pliers. When you clear the drain just drop the stopper back in. Some plumbers lock the stopper in when they install the fixture. I never have for it makes it impossible for the home owner to clean the drain. After you clean the hair pour a 1/2 gallon of bleach down the drain and let it set overnight without using it. Next morning flush it down with a pan full of boiling water.

Sink #2 is the kitchen sink, 1st floor, and the odor here seems less strong, but still present on occasion.
Most bad smells in kitchen sinks are caused by rotting food and grease in kitchen drains and tailpipes Try this for the smell. Tonight before bedtime Take a 1/2 gallon of bleach and pour it down the drains and let set over night. Next morning ,(and this is important) flush out the drain with two large pans of boiling water to loosen the grease and flush the mess out. The bleach will make the crud slippery and began to dissolve it and the hot water will melt the grease and flush the mess away.
. This should make your drains smell better. With all chemicals used in drain cleaning proper ventilation should be observed. Good luck, Tom

CuthbertRumbold
Jul 29, 2009, 10:31 AM
Thanks speedball1 for your suggestions. Unfortunately I have had no improvement after following the steps you outlined.

In the case of the upstairs vanity I've replaced the S-trap and the stopper assembly with new parts. I also did the bleach and boiling water routine on the sink and overflow. So every thing above the trap is either bleached or brand new.

Down in the kitchen I did the same routine with the bleach and the boiling water. The trap, tailpiece, etc here are only about 6 months old, so there wasn't a lot of crud in there anyway.

Any other suggestions on things to look for?

Thanks!

speedball1
Jul 29, 2009, 11:14 AM
Go you hear any gurgles or do you see bubbles in the toilet bowl , like say, when the washer's draining? Tom

CuthbertRumbold
Jul 29, 2009, 03:45 PM
Never any bubbles in the toilet bowl.

I can't hear any gurgle at the kitchen sink or upstairs lav when flushing the toilet or when the clothes washer drains. In fact I can see the water in the trap with a flashlight, and it barely moves.

No odor during any of these tests, by the way.

Thanks!

speedball1
Jul 30, 2009, 04:48 AM
And you're quite certain the smells come from the drains? Traps are supposed to prevent this from happening. While it's possible for a partial clog to develop backpressure and send a bubble of sewer gas back up the line you don't complain of any trap movement. If you weren't so sure it was coming from the drains I would suspect a crack in a vent pipe inside the wall and suggest a smoke test to nail it down. Changing the lavatory trap and pop-up assemble should have cured the problem. To put it bluntly, I'm stumped! I don't know what to try next. Stray smells and noises are the hardest calls that we have. You almost have to be on site yourself.
Perhaps one of the other experts can come up with something I've missed. Good luck, Tom

CuthbertRumbold
Jul 30, 2009, 05:38 AM
Update:

I'm now fairly certain that the odor is the water itself, not anything coming from the drain.

Last night I closed the drain in the lav and temporarily taped over the overflow with duct tape. Then ran some water and bingo - still got the smell. It's sort of a rotten egg sulfur-ey smell with what I'd call a hint of onion :). Funny that it only smells sometimes, and usually only within the first ~30 seconds of opening the tap.

I've ordered a water testing kit from the state of Maine Health & Environmental Testing Laboratory. It's supposed to cover bacteria, hydrogen sulfide and a host of other things. It'll be interesting to see what comes up.

We're on well water here, and have a water softener. The well is shared with three other houses, so I'll ask the neighbors if they have noticed any smell.

Our water heater is an indirect system with a stainless steel tank and no anode rod, so I know it's not that. I've also re-piped most of the house with PEX within the last year.

Thanks for all your help so far Tom... I suspect we may have to shock the well or something but if you have any other thoughts please let me know.

Thanks,
Roy

speedball1
Jul 30, 2009, 05:55 AM
Thanks for the update Roy,
Stinky water huh? We have sulfur water in my area that smells like rotten eggs so I can sympathize. Please keep me informed of further developments. Cheers, Tom