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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Plumbing Questions >> Why no Dergo on 1 stack/drain testing? https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1305470060 Message started by birty on May 15^th, 2011, 3:34pm

Title: Why no Dergo on 1 stack/drain testing?
Post by birty on May 15^th, 2011, 3:34pm

Curious why our new self build house has a stack going up through roof (all 3 are internal stacks) and two other stacks have dergo's on them and terminate in bathrooms/ensuite etc?? Why not dergo's on all 3.
I Have to do a drain test soon- does this mean climbing onto roof with a drain blank and sealing it prior to a testing for leaks?? Can I not simply cut it and put a dergo onto it or does one stack always have to vent to outside air??? :-?

Title: Re: Why no Dergo on 1 stack/drain testing?
Post by greg on May 15^th, 2011, 6:33pm

Usually head of drain is vented. You will probably have to do water test rather than an air test.

Title: Re: Why no Dergo on 1 stack/drain testing?
Post by CWatters on May 16^th, 2011, 7:21am

Think it's the Building regs. I think the furthest stack from the main sewer (eg the head end) has to be an open ventilated stack. Stacks between that one and the mains sewer can have AAV fitted.

Title: Re: Why no Dergo on 1 stack/drain testing?
Post by birty on May 16^th, 2011, 9:01pm

How do you do a water test, remembering that we been in for over a year now and all seems well (and bobed in!!)

Title: Re: Why no Dergo on 1 stack/drain testing?
Post by greg on May 16^th, 2011, 9:34pm

Bag the drain, flush WC until water backs up to WC rim. Allow to settle for a few mins, should then hold level if drain is sound. Remove bag and quickly get out of the way of the rush of water.

Needs to be done on lowest stack connection, ie cloakroom WC if that is the lowest or bathroom / en-suite if that is the lowest etc.

Title: Re: Why no Dergo on 1 stack/drain testing?
Post by birty on May 17^th, 2011, 10:47pm

cheers Greg... And if there is a bathroom on 1st floor and a loo on ground floor -the same stack then i assume still the lowest point is to be tested only?? Also is it the norm for Building control to allow a water test??? (All my externals are ok with an air test- i tried the other day- its just my internals now then i will get BC around once I am happy they will pass...)