"O.B." wrote in message
oups.com...
There should be a trap between the gully and the junction.
After that it should be airtight.

There is a trap leading off from the gully. It was whilst cleaning sediment
from the trap ( yuk! ) that I
decided to do a leak test.

I've decided to bash away the concrete cube that was cast around the bottom
of the soil pipe where
it enters the concrete ledge on the side of my house and have a look. I will
try and post what I find in case anyone is interested, as the leak test I
performed is quite easy for anyone ( with the same plumbing ) to do.

Andy.