nick205
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| posted on 25/11/08 at 09:40 PM |
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Building Question - Soil pipe vent and extractor fan
I'm looking at re-fitting our bathroom and fitting a shower/extractor fan in the process.
The soil pipe runs low level between the bath, basin and toilet then down through the floor and up through the ceiling and roof (all boxed in).
What I'd like to do is remove the section that goes up through the ceiling/roof, cap it with an
AIR ADMITTANCE VALVE at low level
under the bath.
Then fit the extractor fan so it vents out through the ceiling/roof section of the old soil pipe.
Anyone see any problems with this - e.g. overloading the fan by making it push up rather than out...?
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locosaki
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| posted on 25/11/08 at 09:54 PM |
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Hi mate,
You would have to fit a 110mm durgo on the vent pipe 1m approx above the water level of the pan,Under the bath would be to low.Doing it this way,you
could still use the existing vent through the roof to work with your extract fan,Just remember and fit a mushroom cap on the outside.
Mike
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owelly
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| posted on 25/11/08 at 09:54 PM |
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I'm sure the building regs state that the Air Ad Valve has to be in the roof space.
http://www.ppcmag.co.uk
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nick205
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| posted on 25/11/08 at 09:56 PM |
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Useful info guys, keep it coming.
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geoff shep
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| posted on 25/11/08 at 09:59 PM |
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No need to be in the roof. In my last house ( a new build in 1999) the soil pipe ad valve was boxed-in, in the bathroom and was about 3 feet high.
This page refers: http://www.diydoctor.org.uk/projects/air_admittance_valves.htm
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delboy
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| posted on 25/11/08 at 10:36 PM |
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The durgo needs to be above the flood level of the highest fitting, i.e. the basin so what locosaki says is 100% correct. The comment about the durgo
or aav being in the attic is completely wrong, infact, this is almost the worst place for it as the rubber seal in the valve will freeze in cold
weather and fail to operate. The building rges require it set as above, so you could cut the svp and fit the aav at say 1000mm above floor level and
use the remaining section from ceiling through the roof for your fan. As was also said, use amushroom cap on top as the svp cage would allow rainwater
to penetrate the fan.
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YQUSTA
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| posted on 25/11/08 at 11:26 PM |
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If you are putting in a shower unit separate to the bath I would recomend fitting a fan inside there too, also fit the fan on the celing or as close
to it other wise it wont work at it's best.
using a couple of these http://www.tlc-direct.co.uk/Products/BGSLW.html with 1 of these
http://www.tlc-direct.co.uk/Products/MRCFD200S.html would work.
YQUSTA
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nick205
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| posted on 26/11/08 at 08:56 AM |
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Excellent info - cheers gents 
Off to get some bits at the weekend.
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iiyama
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| posted on 26/11/08 at 05:02 PM |
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Have you got two SVP's in your house? Because if you havent you CAN NOT cap the single SVP that you have, the drain needs to be open. A durgo
will only open if a vacuum occurs within the drain, atmospheric pressure then pushes it open. If you have a methane build up with in the drain this is
+ve pressure within the drain and the durgo remains closed. The only way to vent then is through the traps, so worst case is you get a geyser from
your WC.
Durgo's have to be fitted so that they are level, (or higher), with the highest trap.
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delboy
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| posted on 26/11/08 at 06:33 PM |
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The last comments aren't quite correct, the BBA certification for Durgo valves states that there must be at least one vent pipe on the sewer for
no more than 6 houses, to the best of my recollection. BBA ( British Board of Agrement) are an independant certification body for construction
products and systems and are accepted as authoratative by all UK Building Control Authorities.
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iiyama
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| posted on 27/11/08 at 09:31 AM |
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That may be correct bud, but how are you going to know? What if you have a situation where all six houses cap the pipe? Neighbours dont talk much
nowadays, certainly not six houses up the street! 
If your in a detatched house miles from anywhere youll be on a cesspit no doubt and maybe have only one vent there.
In fact there are many situations where I can think that an AAV shouldnt be fitted.
New build is a different issue altogether, but as people modify their houses I can still see problems ensueing!
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