Chris Green wrote
| The bath is in a flat and is positioned about two or three meters
| from the main service duct where the sewage downpipe is. The
| waste pipe from the bath runs essentially horizontally from the
| trap under the bath across to the downpipe. Not surprisingly,
| especially towards the end, it drains very slowly. It's impossible
| to get at the connection of the waste into the downpipe as it's
| inside a brick built service duct, all you can get at is a 40mm
| 'socket' where it pokes through a hole in the brickwork.
| Can anyone suggest any clever ways to improve this?


Chris, are you absolutely sure that the entry into the foul downpipe is
truly clear? I had a similar problem in one of my flats that I eventually
traced to 'rusticles' on the inside of the cast iron down pipe catching a
hairball. Nothing was visable in the branch pipe until it was stripped out
to a bare socket when with a torch the problem was obvious and easily cured.

Another possibility is something I found in my own house. Basin waste pipe
joins main pipe from bath to downpipe at a 'Tee' which had been installed
with the 'swept' branch flowing towards the basin rather than towards the
outlet (yes I must have done it many years ago when I changed the bath -
1985 I think!). Turning the Tee made a vast difference.

Andrew Mawson