In our kitchen, when ever the washing machine or dishwasher pump out there
is an annoying gurgling from the sink. It's never been annoying enough to
make we look at it till now

Since getting a new washing machine which obviously pumps out quicker than
the ancient totally knackered hotpoint that it replaces occasionally (and
I can't reproduce this when I try!) it will pump over the standpipe slightly
and start to flood the kitchen...

Just dismantled the bits I can get to and while they were a bit sludgy it
wasn't anywhere near as bad as I expected so I'm assuming there is a partial
blockage somewhere down stream. It's had a load of Mr Muscle gloop and a
couple of hours ago I poured two buckets of nice hot caustic soda down the
sink and let it strew. Much gurgling but no difference :-(

A diagram of what we have at the moment is on http://bogit.com/tmp/plumbing.png
(apologies for the total lack of artistic talent :-)). I know the pipework
is clear to the T where the sink connects. Beyond that is my problem

immediately after this T the pipe goes through the wall, turns 90 degrees
and disappears into the foundations of the conservatory - this 90 corner is
inaccessable (The T piece is pretty difficult and I'm concerned that if
I undo it I'll never get it watertight again). The corner that is outside
is also in a position that is impossible to get to due to it being squeezed
inbetween out convervatory and nextdoors wall. Even if I could get to it
it is solvent welded with no spare pipe before it vanishes into the
concrete to allow me to cut it off and replace :-(

Given that chemical warfare appears to have had no impact at all I'm
pondering my next move. Are those drain cleaner things that you wind
down the plug hole likely to be any good? Will they go around a 90
degree corner without problem?

If not, any ideas what might? Curtain wire springs to mind as a possibility

Also, once I sort this I'm tempted to stick an antivac trap on the sink to
stop the gurgling once and for all. Good idea or asking for more hassle?

Gah. I hate plumbing

Cheers,

Darren