Ever since we moved into this house a few years ago, the smell coming from the sink in the main bathroom has, at times been pretty strong. It’s not always there, but the last few days it’s been strong, and with a slight sulfuric smell.
Occasionally when it gets bad, my wife will pour a container of hot water down it and that seems to work for awhile.
A couple of years ago I had to change the P trap under it, so I know that’s not the area of concern.
A couple of things of note, directly under this bathroom is a basement bathroom, with a toilet, shower and sink, and there are no odor issues there.
Also, apparently a few years before we bought the house, it was hooked up to the city sewer, so prior to that it was on a septic system.
Which brings up this note, just outside the wall of the house on the side these two bathroom are, there are two 10" pipes coming up to the surface. Septic clean-outs? Does this mean the house had two septic tanks? I have never taken the tops off these pipes, but maybe I should.
And there are two other bathrooms in the house. No issues with them.
The water itself may have a sulfuric odor.
I have experienced this in northern Illinois. My kids called it “egg water”. But since this is only the one sink we can rule that out.
The “P” trap is dry.
This will allow sewer gas to back up into the bathroom. The trap may be drying out because a suction created somewhere else in the piping system pulls the trap water out to the waste pipe. I saw Tom Silva from “This Old House” discuss a similar issue a while ago. I think it had something to do with the vent pipe. I can’t give you any details but he made it sound like a real easy fix. Ha! You know how that goes in real life.
The problem is the actual sink itself.
There could be some funky stuff growing inside the inner bowl. You know where the hole for the water overflow is? It’s dark and damp in there and all kinds of nasty critters like that kind of environment. See if you can get some bleach in there.
That’s all I got. I’m certainly no expert and I feel your pain man. I hate plumbing.
Try closing the trap and let the sink overfill with hot water so that it drains into the overflow hole for a few minutes, maybe try pouring some bleach into the hole first…
When your bathtub drains or you flush the toilet, this ends up sucking air into your plumbing. If that doesn’t make sense to you, consider just a straight vertical pipe. If you fill the pipe with water then let all of the water drain out through the bottom of the pipe, at the top of the pipe you’ll have this gap where the water used to be, creating a vacuum. Air will rush in to fill this gap, and there’s your suction.
When you don’t have anything going down the drain, though, sewer gases can come back up from the sewer pipes. The way you stop these sewer gases from getting into your house is you put p-traps in your sinks and then put a vent pipe at the top of your plumbing stack. The water in the p-traps stops the gases from going up through your sink, and the vent at the top allows the gases to escape.
When water goes down the pipes (draining bathtub, flushing toilet, etc) that vent pipe at the top is also where the air will be sucked into the system.
If your vent pipe is blocked, then the suction will pull the water out of your p-traps so that it can suck the air in through the sinks, and then you no longer have an effective p-trap. Not only does the drain system suck in air through the p-traps, but it also lets sewer gases come back out through your sinks. This might be what the OP is smelling.
If the vent pipe is blocked, the air can also be sucked in through your toilet (which kinda functions like a p-trap) causing it to glug and maybe drain. If your toilet glugs every time your bathtub drains, the most likely culprit is a blocked vent pipe.
Fixing a blocked vent is as simple as figuring out what is blocking the vent and clearing it. Sometimes birds will build a nest in the vent at the top of your house. Sometimes the wind will blow a piece of debris in there. Sometimes a bunch of killer bees will clog up your vent pipe with a huge nest. So yeah, sometimes clearing out the blockage is easier than others. If critters have built some kind of nest deep inside the pipe where you can’t see it from the top, that’s going to be harder to find and clear than a four year old bird nest that has long since been abandoned right at the top of the vent that you can just grab and yank out of the way.
This is the line that caught my attention. If the bathroom in the basement is used at all, I’d make sure it (and the problem sink/bathroom) are properly vented, such that flushing the toilet isn’t siphoning the water out of the sink. You could call a plumber or inspector, but the easiest way is probably just to pull the stopper out of the sink and the next time it smell make sure there’s still water in the trap*.
This is, of course, assuming that there aren’t other issues, such as an improper trap, clogged stack, or some other plumbing/venting issue.
That’s where I’d start, make sure there’s water in the trap. If there’s water in there, what you’re smelling likely isn’t sewer gas and you can eliminate that and work on problems between the trap and your nose rather then the very general ‘something’s wrong with my plumbing’.
However, if it’s easy, it’s not a terrible idea to A)pull the trap out and clean it, they do get gross and B)pull the drain stopper out and make sure it’s not covered with a big wad of nasty rancid grease covered hair…also gross.
*Well, not just ‘water’ but enough water, it has to be high enough that the seal is maintained.
If yes, read about “shocking” your well water. Search google.com for the words" shock well water
Also hot water piping in the walls can have an air bubble. Usually to a pipe going up which was terminated and is no longer used. Bacteria grows in this and you get a rotten egg smell in the hot water. The section of pipe needs to be removed or the air let out of it (open valve to allow water to flow in that section of pipe and flush it).
Is there gurgling when you drain that specific sink? The vent pipe should be sticking out your roof, and it’s easy to determine if that vent pipe is connect to your bathroom sink. This really does sound like a venting problem.
Try going “long” with your wife’s idea … bring a couple gallons of water up to a rolling boil … cut the heat … add a good amount is dish washing soap … stir … pour this down the bathroom sink … maybe preheat the drain pipes by running hot tap water down first. It’s a long shot but you did say it helps the problem for a little bit.
Why don’t you use disinfectant or toilet chemicals to remove and clean any smell or stain.If you clean your bathroom 1 a week no smell will come.Im sure of it.
Do you have well water? We had an old house on a well and some ancient plumbing.
One bathroom sink would develop a slight sulfur smell in the summer and not be noticeable in the winter. Plumber said it was iron bacteria in the water, maybe a pipe on the route to that sink has a stagnant place/along with plumbing corrosion.
It was in the water coming out, you could smell it holding the water in your hands, not from the drain per se.
And it was the only sink with the smell.
We sold the house before we could upgrade that part of the plumbing. It was obvious that the well had tons of minerals and iron from the deposits it left on fixtures.