DIY Doctor UK DIY Forums

Hey Docs

I'm putting in a new toliet in a single storey extension to my ground floor flat. (converted victorian semi).
How high does the waste pipe vent need to be - full height of the existing buiilding or just to the roof level of the new extension? Does it make a difference if there are windows above? I heard about internal valved vents but not too keen on the idea. Any advice?

Cheers

Jos

A soil vent pipe should always discharge to external air unless an air admittance valve is fitted. The top of the SVP should be a minimum of 900mm above any openign into a dwelling within 3m of the pipe.

The internal valve is an air admittance valve and they are a non-return type of valve - lets the system vent by letting air in but not the air (and smells) out. An air admittance valve must be positioned above the highest water level of any appliance that connects into it - normally the sink.

ok thanks thats helpful,
its an unusual site in that the extension is sited at the bottom of an enclosed light well, i really dont want to run the pipe right up three stories to the top, but there are windows above facing in all the way up and the total area of space is only about 3mx2m.

Would it be permissable for an external svp to be less than 3m from windows if i stick an aav on top of it?

related to this, the bathroom in its current position drains with no svp and functions fine, is it absolutely mandatory to have one at at all?

thanks again

if you install an AAV then you can go within 3m of a window however there is a very limited number of AAV that can be used externally. Some appear to claim that they can be used externally but they do not anything such as a BBA certificate for this purpose so are unlikely to be accepted by Building Control.

Under certain conditions it is not necessary to connect toilets, etc via a SVP into the drainage system but there are numerous factors to consider, all site specific. I would recommend you consult with your local Building Control Surveyor.