I live in a bungalow and in the future i plan to convert the loft into a bedroom and fit a roof window. According to Part H building regs the soil vent pipe needs to finish 900mm above any window within 3m of the pipe. The window will definately be within 3m of the pipe but extending the soil pipe 900mm above the top of the window would obviously look obsurd. The building regs also refer to an Air Admittance Valve but say that they can't be used outside. As I am about to start some maintenance work on the sewer pipes I thought it would be a good time to address the vent pipe dilema but i don't know what the best solution would be - any ideas???
An air admittance valve (aav) can be fitted with certian restrictions as follows:-
It must be internal and the insulating cap left in pace (it looks like a packing piece)
The aav must terminate above the highest flood level of the appliances fitted. Normally a WHB overflow. Presuming that you do not have rooms in the loftspace this should be very easy ie. anywhere in the roof void.
The head of the run of the drainage system should have an open vent. In a bungalow (detached) you should be OK as I am sure your nieghbours will still have an open SVP.
Failing all the above you could redirect the SVP away from the window. Above the services it serves you can have bends, reduce to 75mm diameter and terminate through a tile vent if you wish!