wrote:
I've got a washing maching machine connected to a waste pipe via a
standpipe and p-trap.

Do you mean like this? http://www.wickes.co.uk/invt/431915

I've now purchased a dishwasher and would like to connect the waste
from the dishwasher to the existing arrangement by replacing the
p-trap with an appliance nozzle trap.

The appliance trap is really designed to replace the trap under the kitchen
sink, never heard of them being used to replace the trap on a washing
machine trap.

You can get a double appliance trap.


--
Dave
The Medway Handyman
www.medwayhandyman.co.uk
01634 717930
07850 597257