hi charl this is a well known fault with washers that drain into the sink u bend
what happens is the u bend gets slightly blocked so when you put water etc down the sink it runs into the washer because the sink cant get rid of it quick enough
try plug hole unblocker or even better take the u bend off
anymore problems
Here are two very helpful web sites http://www.freewebs.com/msdapudsey1
http://www.freewebs.com/cbrsleeds
phil grimshaw
August 2007