"Bigus Dicus" wrote in message
m...
So you need an open exhaust somewhere downstream of every bog to prevent
pressure build up, and an inlet somewhat upstream of it, to stop partial
vacuums.

Thanks, but I am still a bit confused. If I currently have just one
bog, dowstairs, and no soil stack open exhaust above my roof, then
presumably:

(a) I have an AAV somewhere in my downstairs bathroom that services
only that bog (I am not allowed to take the floorboards up at present
as the M-I-L is coming to stay)

(b) Somewhere downstream of my bog there is an open exhaust, although
this may be to service multiple bogs in my and my neighbours' houses?

So if I put the new upstairs bog in, I will definitely need another
(a) dedicated to the new bog, but the same (b) can service (perhaps)
both the new and the old bog, as well as neighbours' bogs?

Please advise - I am VERY confused!
Thanks...

Sorry I haven't been following the thread, but the jist of the problem is installing
another loo in an upstairs room (?) correct. This would depend on where the new loo
would be sited to correspond with the original downstairs loo and where the pipework,
mainly, for the waste extraction.

Do you have an internal soil stack built in to a corner or behind the plasterwork in
the original loo ? Have a look to see where the pipe from the back of the existing
loo goes and from there you should be able work out where the soil pipe is in relation
to the walls. Does the loo pipe go directly through the wall to the outside. Does it
bend and go into a boxed in soil stack in the corner of the room ? Does it disappear
through the floor ? When you flush the loo, can you hear the flowing passed in
another room beside the loo ?

Once you find out where the existing soil goes you're on your way to being able to
makes plans for the new loo. You don't even have to use the existing soil stack pipe
if you find out where the sewerage system is in respect to you property. It might be
possible, or even easier, to take a new soil pipe from the new loo directly to the
sewer system near you house. The pipes are cheap to buy, it's the fitting that cost a
bit more in terms of drilling and digging and things.