Bad smell from bathroom sink

[Trevhut]

I have a problem with an upstairs bathroom sink. There is a strong rotten egg smell which only happens after the tap has been turned on. Using bleach helps for a few days then the smell returns. I had the trap replaced but the problem came back. It seems strange that the smell only comes when water is introduced.
Any ideas out there?

 

[Fallon1982]

Try getting an anti siphon trap. Or a non return valve cut into the waste pipe. So water will pass through but won't let the smells back up. May be a faulty trap. I'd get whoever replaced the trap back if you've paid and the jobs not fixed properly!

 

[JCSPLUMBING]

You have a siphon issue. Probably down to an s trap created out of a p trap with elbows. Get a an anti vac bottle trap and you should be ok.

 

[townfanjon]

Anti-vac traps everytime

 

[kozak1968]

Try bleach down the overflow. What can happen is the basin internal overflow can trap water. A film covers the water and as soon as the film breaks when you open a tap, the contaminated water releases the bad egg smell.

 

[zzzjim]

Is/was the sink draining properly ?
( may be problems else where ..trapped GAS )