if It's water from the sink you don't need a one way valve, just raise the water outlet pipe so it is higher than the waste on the sink. simples !!
mr. fixit, April 2010
either filling from trap under sink if water is cloudy or e/valve is passing and will be required to be replaced.
john, February 2007
I'm no expert but a friend of mine had the same problem and it was the water from the sink going up the washing machine's expeler pipe... to fix it she had to put a one way valve on the explerer pipe and then this stopped...
