wrote in message ...

Why have running traps? I use a standard washing machine trap and
standpipe,
with a t piece above the trap, and the second input coming in from the
side.
It has successfully worked for 17 years with two washing machines.

I already have one running trap, but the one I would have to buy could be a
w/m trap. Front-to-back space at the back of the cupboard is limited by the
shelf, which might be an issue though ...

You /are/ using 40mm pipe?

Yes, same size as original sink and w/m waste fittings ...