Removing Internal Soil Stack & Venting

[billyonemate]

A builder moved my bathroom some years ago put in a new external soil stack for the WC (all good). But, he left the old internal soil stack in place because the kitchen sink and washing machine emptied into it. Recently i removed most of the internal stack and capped it just above where the kitchen sink & washing machine discharge into it. But i started getting foul smells in the kitchen - i think from where the washing machine discharges into the pipe as it is not sealed. On the advice of a friend i fitted an inline u-bend between the washing machine inlet and the capped soil stack. So far this has gone ok, but its only been a day or two. Will this be enough, or do i need to vent the old capped soil stack somewhere, like a hopper head does on the old Separate Drainage Systems?

 

[Madrab]

When you say you removed most of the internal stack and capped it, do you mean 110mm soil stack pipe? If so did you install an an automatic air vent (AAV) as the cap or just use an end cap to seal it? If the WM didn't have a trap then chances are that has been the issue.

You need to be careful when altering soil stacks to ensure you haven't removed a required soil vent pipe.

 

[billyonemate]

Yes, the 110mm soil stack pipe. Didn't use an AAV, just capped it, the new soil stack does vent externally, the new stack & the old stack meet at a manhole outside, so hoped the old stack would vent via the new one when not under pressure & via the attached neighbours stack when under pressure?

 

[bernardgreen]

A builder moved my bathroom some years ago put in a new external soil stack for the WC (all good).

Does the new stack go to a open vent at or above the roof line / metre or two above highest window. If not then it is NOT (all good )

If you have removed the only vent to the soil system on your property then you have a potential problem of sewer gas forcing its way past U bends if ( when ) there is a pressure build up in the sewers. Flushing a toilet into an unvented system can create enough pressure to push sewer gas past U bends for sinks / wash basins / baths etc

 

[billyonemate]

Yes, the new stack has an open vent that exits above the roof line, the question i am asking is do i need to vent the old capped soil stack?

 

[Nige F]

No you don't - in effect it has become a Stub Stack.

 

[billyonemate]

Thanks Nige - i was hoping that was the answer

 

[polesapart]

No you don't - in effect it has become a Stub Stack.

+1