Overflow discharge pipe

If you use a common pipe, it is possible (say if the outside discharge pipe got iced up or otherwise blocked) for the inhibiter-laced overflow from the central heating pipe to end up in the cold water supply.

Not perhaps what you want to be cleaning your teeth with..

Thanks Sue.I can see that is a possibility but it just puzzles me that I do not see any of the other same type of houses with two pipes sticking through the wall and I should think that some are bound to have the same type of Water/CH set up

Tab

I have just one. The cold water overflow sits about 6" above top centre of the central heating tank. The central heating tank's overflow is piped outside. It does mean that the cover of the central heating tank has a big hole in it, lining up under the pipe. The air gap means that it is not possible for water from the treated tank to get into the pure water tank - only into the loft...

Most of the other lofts I have been in seem to have had two..

I think I will just have to stick with what I have got.It is quite safe and I am the only one who seems to bother about two pipes coming out of wall .Wife does not want to know about discharge pipes etc :-)