I've got a sulphur/sewer gas smell coming from my bathroom sink, I've pulled off the P trap and it's full of water, which should block the smell. Any suggestions?

Yeah stop getting drunk and shitting in the sink.
















How often do you use this sink? If not very often the water in the trap gets funky. Do you have well water? Sometimes the water will be high in sulpher and the first couple of gallons that come out will have the sulpher smell.

City water, the sink is used several times a day but I get the funky smell when it's been about 4 hours since last use. I'm pretty sure it's not the water supply it doesn't' smell anywhere else in the house and only near the sink when I'm brushing my teeth (or taking a dump ) I have changed the sink and faucet (renos, not because of the smell) and the smell persists.
I'm thinking maybe somehow the gas is bubbling up thru the water in the trap.

Where is the sink in relation to the end of your sewer line? Maybe you need a larger trap or a check valve.

Maybe the trap doesn't drop down enough and there's a small air gap?

There is a fix for this, but I can't recall what it is. My parents have something that purges the sulphur gas out of the system so you don't smell it at the taps.

Do you only get the smell when you turn the taps on? If so, it's probably coming from the water, not the drain.

I get the smell when the taps are on I thought it was the water at first and by doing a few tests like putting the plug in the drain and filling up the sink with water I don't get the smell. I'm wondering with the water running if the flow of water is making the trap empty partially, allowing the smell to come up. The tap water everywhere else in the house smells ok.

Click to view attachment

Check the stack vent. Make sure something didn't build a nest on it.

Good call Dion I forgot about that one

Good call Dion. That's where the problem most likely is. If the vent is plugged you'll get gas coming back up through the traps when you flush the toilets etc.

Thanx for the info I'll get up there tomorrow, after the snow melts. I suspect it may be the washing machine. I haven't used it in a few days and no smell, I've used every other water fixture since then. Is it possible the pressure and flow from the washing machine is too much for the stack and causing suction to empty the p-trap in the sink? It would probably suck from there if the vent is plugged, the sink is the closest fixture to the vent.
Any roof walkers wanna get up on my roof for me?

The P-trap keeps a water seal between the vent and the fixture, so the odor is not likely from the vent. Check the sink overflow, the hole near the inside top of the sink away from the faucet. They can get a stinky build-up so pour some bleach through it. Are you getting odor from just one fixture? If so it is drainage, as stinky incoming water will affect many fixtures.

Strangely enough since this spring the smell is gone. I'm wondering if it was the vent which had partially frozen over and causing the drainage to become a closed system, trying to balance pressure thru the weakest link, the bathroom sink, thereby emptying the p-trap. I'll also look into the overflow as you suggested, it could also be my GF has moved in and the sink is getting used more than twice a day too.

Stop taking a dump in the sink

Yes, NEVER dump where you scrub your fangs