My home (built circa 1990) has two soil stacks, one serving a bath, loo and basin on the first floor and the 2nd serving a shower, loo and basin on the first floor and a cloakroom on the ground floor. As part of redoing both bathrooms I would like to use air admittance valves instead of the current 80mm soil stack extensions that go through the roof. In another thread (//www.diynot.com/forums/viewtopic.php?t=155359&start=0&highlight=) I read that the drains must have at least one vent. What constitutes a vent? There are access points in the ground to the drains at the front and rear of the house, the rain water downpipes feed into the drains and outside of the house there are what appear to be hoppers by the kitchen and utility room drains (not adjacent to the sol stacks) where water can be heard running when he kitchen or utility room sinks are draining.
So my question is: can I install 2 air admittance valves or just one?
So my question is: can I install 2 air admittance valves or just one?