We are thinking of installing a bathroom in a loft conversion. The problem is location i.e. the bathroom would be at the front but the soil vent is at the back of the house. The problem this creates I understand, is that it would create a siphon effect sucking the water out of the toilet bowl when it is flushed resulting in the full smell of the sewer coming up the pipe.

To resolve this, we have been told to install a DERGO valve. Does anyone have any experience of installing one of these or knows of a website we could look for more info?

commonly used - i have one in my house. it lets air in, but not out to eliminate the siphon effect
http://www.diydoctor.org.uk/projects/air_admittance_valves.htm

Richard

Many thanks for your assistance. Kind regards.

Shower only instead of bath i take it,because of hot water tank height!

an air admittance valve in the right position will stop any syphonic action from taking place. make sure you have the correct fall on soil pipe to wc. be carfull where you connect shower as you do not want soiled water comming out of the wast pipe if you get a blockage. check bs 5572 for bylaws regarding soil/vent pipes as you can fail building regs if not correctly fitted

Why cant the bathroom be at the back?

You might want to investigate Saniflow's - they're a pump / macerator that sits behind the wc pan and don't need a 110mm soil pipe so it might make connecting to the existing SVP a bit easier. They don't allow smells back in either.