On Mon, 14 Mar 2016 01:01:50 -0700 (PDT), harry
wrote:

snip


The problem is getting any chemical actually in contact with the blockage.

Quite, so nothing like having the pipes out and in the sink and washed
out properly. ;-)

The longest pipe run goes under the corner bath and terminates in an
access point that has a removable lid for cleaning / rodding etc. I
fitted that directly under the corner seat of the bath so that if I
had to at any time I could cut a hole in the seat and fit an
watertight access hatch etc.

Cheers, T i m