sewer gas

[helen5]

we live in the top flat of a converted victorian house. when we drain water from the bathroom sink, there is often a smell of sewer gas (horrible sulphur smell) which comes up through the kitchen sink. i have tried using drain cleaner to clear any blockages. i have also checked and cleaned the P-traps under both sinks. when we drain water from the bathroom sink, sometimes water bubbles up through the bath, although this does not seem to be accompanied by a smell.
Old british houses (ours included i think) usually have 2 drainage systems - the sewage from the toilet is drained via one system, and waste water from the sinks/bath etc via another. I do not understand how this horrid smell is coming up through our sink - if anyone has any ideas, please let me know.
thanks, helen

 

[Bahco]

Sounds like your traps are losing their seal.

Plunge a straw into the sink hole and place your finger over it, withdraw the straw and you should see 75 mm of water in the straw.
Obviously if there is no water present then you are losing trap seal and need to address this.
You may need an anti vac trap or reconfiguring of your waste pipes.

 

[helen5]

thanks - i will give the anti vac trap a go.

 

[Bahco]

Is there any water in the trap?

 

[helen5]

there did seem to be water in the trap at the time i tested, but the smell only occurs sometimes (especially late in the evening for some reason).
i wonder whether pressure in the pipes caused by draining the bathroom sink is causing bubbles of smelly gas to come up through the water in the trap, rather than causing a total loss of water in the trap - is this a possibility?

Surely it must be a problem with the trap seal, as the smell could not get up through the sink drain if the seal is in tact?

 

[Bahco]

If you have the required (and tested by the powers that be) 75 mm water in your trap at all times, no smells can come back to haunt you.

Is your waste pipe a single run or does it connect to another appliance.
If shared waste, change it to a single.

 

[helen5]

The only appliance we have is the washing machine - the waste pipe to this is connected to the drain for the kitchen sink (before the P-trap) - i presume this is a 'single run'?

If we are getting air coming up through the trap due to an increase of pressure in the drain (rather than siphonage due to decreased pressure) will an anti vac trap still help with this?

 

[Bahco]

Try the anti vac trap first.

The problem is loss of trap seal which needs addressing. Maybe your fall is too steep.

 

[kevplumb]

or fit a hep v o trap

 

[Nige F]

if we are getting air coming up through the trap due to an increase of pressure in the drain (rather than siphonage due to decreased pressure) will an anti vac trap still help with this?

NO...But a HepV0 one will..kevplumb posted link

________________________
moderator

edited to correct link

 

[helen5]

the smell is coming up through the kitchen sink - is it ok to fit a hepVO trap in the kitchen, or should they only be used in bathrooms?

 

[kevplumb]

can be used on anything

 

[Nige F]

And horizontaly or vertically They are the business.

 

[2scoops0406]

or fit a hep v o trap

That doesn't look like a piece of plumbing kit, you sure you got the right catalogue

 

[chrishutt]

Kevplumb always gets the right catalogue - the guy's a living encyclopedia of plumbing fittings.