extractor fan

18 May 2007
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United Kingdom
Can anybody suggest a reason why I shouldn't have ducted my cooker extractor fan into an internal 110mm waste stack (mushroom fitted on top). Waste stack is full of fresh air (no smells at all) and duct is fitted with spring-loaded in-line backdraft shutter as additional precaution. Connection by 125mm aluminium duct into 110mm branch 2m from mushroom on roof. Works a treat and no finding an external wall, knocking a hole etc etc. I'm sure there'll be a byelaw somewhere...
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Why did you do it if you know you shouldn't have?

There may not be any smels, but that soil stack / vent pipe is a direct branch off the main drain, which may contain other peoples' 5h1 and other excrement :eek: MMM lovely bacteria. By playing a fan into the pipe, you may be inadvertantly drawing air from the drain system (which is what the went pipe is there to do anyway!)
so no byelaws then - everything downstream has a trap hence no direct connection to gas in sewers - to draw over any of these traps would need something slightly bigger than an extractor fan...irrelevant anyway as :D tiny positive pressure in stack not vaccuum...
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vent pipes have no traps between them and the sewer, since as you say, quite some pressure would be required to overcome the water in the trap.
I have an interceptor trap - maybe this is why my stack is so fresh - I will remove the one-way shutters and stick the wife's canary in the pipe for a day or so...... :evil:

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