Hi,

During the course of investigating a blocked waste pipe, I've been
forced to become more familiar with the kitchen plumbing as installed
by my house's previous owners.

Firstly, how much of a problem is it if the pipe after the u-bend
(between the main soil pipe and the u-bend) has an upwards gradient?
The current installation has a slight upwards gradient, which (not
least) I think means the sink does not empty quickly.

I think it has this upwards gradient because a sink and dishwasher have
been plumbed in between the u-bend and the sink. This has pushed the
waste-end of the u-bend lower than originally intended. Does anyone
know if there's a way of plumbing in the dishwasher and washing machine
to bring the u-bend outlet higher? Can I just insert a small length of
pipe to achieve this?

Finally, the pipe to the waste pipe and the u-bend have been joined
particuarly badly. Basically, there is no seal/o-ring and the pipes
are different diameters! I can't see how it could ever have sealed
properly (to unblock the pipe, I had to unscrew it and it now no longer
seals). What's the best way to join these pipes together?

Suspecting this job may have hust got larger than anticipated ....

Miles