Foul smell of sewage downstairs when upstairs toilet is flushed

[veedee]

When upstairs toilet is flushed, the smell of sewage reeks in the kitchen and around our staircase

What could the possible cause and what remedial action do I need to take?

The soil stack is in the kitchen and the plumbing is only a year old and never had an issue before.

 

[Harry Bloomfield]

Is the water in the kitchen traps, being sucked out? Check whatever type of vent you have is working properly, if the vent is indoors, it will be automatic vent, allowing air in, but not out like a valve at the top of the vent stack.

 

[just pumps]

Lift the manhole cover and have a look there for starters.

 

[blup]

Flush the toilet with loo paper and have someone check the flow at the manhole. If no obvious blockage or bottle neck, it would be a loose joint from the toilet or other waste pipes where they join the soil stack. It may need to broken open if its boxed in, so if you're not confident or competent to check all this, best call in a plumber.

Blup

 

[HERTS P&D]

Blocked manhole/drain line.

Andy

 

[veedee]

Blocked manhole/drain line.

Andy

I haven't lifted the manhole yet. But the water appears to be flowing well

If the manhole/drain line was blocked, wouldn't water back up when I flush the toilet? or do the washing?

Is the water in the kitchen traps, being sucked out? Check whatever type of vent you have is working properly, if the vent is indoors, it will be automatic vent, allowing air in, but not out like a valve at the top of the vent stack.

The soil stack runs from upstairs bathroom straight down to kitchen on ground floor

The soil vent then runs up into the loft and through the ceiling

 

[BlueLoo]

Agree with Harry that its likely the u bends being evacuated on flush.
Could be positive pressure from the flush pushing air out in the stack joints (check with soapy water).
Could be a leak in the u bends causing the seal to be lost.

Fill up the ubends with a coloured liguid and what what happens when flushed.
Check any stack joints for air leaks.

 

[Hugh Jaleak]

Lift the manhole cover and have a look there for starters.

Do this and report back.

 

[Harry Bloomfield]

I haven't lifted the manhole yet. But the water appears to be flowing well

If the manhole/drain line was blocked, wouldn't water back up when I flush the toilet? or do the washing?

Depends really on how badly blocked and the speed that water is put down it. Completely blacked, as happened to me once - yes it would back up. Hence I suggested checking the air admittance isn't jammed, at the top end of the stack.

 

[Harry Bloomfield]

The soil vent then runs up into the loft and through the ceiling

Major point - does it emerge through the roof?