Thanks for the reply. The white waste pipe is from the bathroom sink & is joined (not shown in pic) from the hand basin in the toilet & discharges into the soul pipe about a metre below the AAV
We recently moved into a Victorian terraced hose and think there is a problem with the AAV Dirgo valve installation possibly fitted in previous renovation when an outside stack seems to have been removed to accommodate a conservatory style roof installed to replace a slate/tiled lean to roof.
As...