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Andrew Smith
Andrew Smith, Plumber
Category: Plumbing
Satisfied Customers: 3776
Experience:  City and Guilds qualified plumber
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I have a 3 storey grade 2 listed house and am currently

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I have a 3 storey grade 2 listed house and am currently upgrading the bathroom situation. There is a toilet, a shower, 3 sinks a dishwasher and a washing machine at ground level. 1 of the sinks drains into an open gulley outside. the second floor has a bath, a shower, 2 sinks and 2 toilets, and the top floor has a bath, sink and toilet. Due to the listing we have to put the soil stack internally and can only put a vent stack on the roof top. The problem is I can only fit a 2"- (3" at a push)- pipe between the rafters to get out of the roof. I am considering using a Studor AAV which appears to be able to cope with all of the above and can terminate in a duct in the loft bathroom. My plumber is not keen on AAv s and i wonder if we are asking for trouble not having any open external vent at all? Would it be possible to use the Studor AAV but also have a 2" open vent coming off the soil pipe just below the Studor Valve and out through the roof? I would value your opinion and any recommendations. Thanks
AAV's are good.
We fit them in hotels a lot for short stacks.
If boxing in then you should vent the boxing with 100cm2 vent.
Any additional vent to atmosphere will help if everything is running at once.
Customer: replied 4 months ago.
Hi Andrew,
Thanks for your response. a few more questions for you.
- Would you consider using an aav alone or is it definately worth the extra investment to add a 2" open vent through the roof?
I have been wondering what would happen to the gases in the AAV system pipe if we were to shut the house up for 6 months?- Have you used the studor aav? - it looks simple and well made and comes with good reviews?- what make would you recommend?- If we go for the aav plus a 2" outlet where would you fit the open vent ? do you know whether it would compromise the operation of the AAV - or doesn t that matter?Thanks so much for your help. greatly appreciated.
If you fit the 2" vent then the AAV would only be needed if the suction pressure became great enough to trigger it.
Perhaps 3 toilets flushed concurrently or 2 baths emptying.
I usually use the Hepworth one due to cost restriction.
It only draws air in so any gases could accumulate at the top if the stack if not used for a while, but on first use again air would get drawn in and disperse any build up.
Customer: replied 4 months ago.
Thanks Andrew,
So, is the 2" vent plus the aav the best solution do you think?
The roof penetration is best and then you have the AAV as back up under heavy use.
Customer: replied 4 months ago.
That s great thanks.
No problem.
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