Harv wrote:
Hi all,

The Problem :-

I have a conservatory style plastic roof over a room on the side of
the house. The waste stack runs up the inside corner of this room,
and out through the current roof, where much flashband has been
applied to stop it leaking.

However the current roof is a very poor consruction, nearly flat and
only 10mm thick. Oh, and it leaks too.

The plan is to replace the whole roof with a self supporting UPVC
system with 25mm thick multiwall glazing, increasing the slope of the
roof at the same time.

With the increased slope, it would be sensible to fit an air
admittance valve above where the toilet connects into the stack, but
the valve would actually be below the level of the trap in the hand
basin. All of this would be inside the room, but the stack would not
need to penetrate the new roof.
The valve should be above the overflow for the basin.
Is this likely to cause any problems?
Presumably the valves do not allow any odour to escape?
In theory, mine don't. They are least 1m above anything that can feed into
the stack