Washing machine draining into dishwasher

[Heyyouitsme]

Hey guys, dont flame a newbie if this has been asked before, i didn look through about 15 pages and found nothing.

Right when i moved into my house i had a waste connector under my sink for a washing machine, i unscrewed this and put on a 'Y' piece to allow for my dishwasher waste to be connected also, anyway whenever i use my washing machine some of the waste makes its way into the dishwasher, and im guessing the same happens when i use the dishwasher, ie some of the waste gets into the washing machine. I tried putitng the original single waste connector and using the sink overflow as the other waste point, so there was a gap between the 2 waste pipes, but water still managed to get into either appliance.
I think ultimatly my problme lies with the fact i dont have a massive fall on the sink waste pupe after the 'u' bend (the section that exits out of the wall) but by the looks of it this is due to there beig limited space, thus not allowing any greater fall.
Is it possible to get a non return valve that can be fitted to each waste line to stop this, and if so what is it called. or is there another solution

sorry for the huge post, )

 

[Sleepyhead]

Run the drain hoses from each appliance so that they go as high as the underside of the sink drainer then back down to the spigots. It won't backfill this way.

 

[Heyyouitsme]

didnt even think of that, how simple, so fix to the underside of the worksurface.

thanks mate

 

[Heyyouitsme]

doh, tried this and still backfills slightly, both waste pipes are now as high as i can possibly have them. ANyone with any other suggestions?

 

[Sleepyhead]

If it's still backfilling then you must have a partial blockage in your drains or your drainage system is poorly designed.

 

[Heyyouitsme]

the fall from the pipe that goes thru my kitchen wall from the u bend is not that great, but that said when i empty the sink it empties quick enough. i take it there is no such thing as a non return valve then?

 

[Heyyouitsme]

guess not then, thanks guys lol

 

[JohnD]

there is an alternative method of fitting the wastes from appliances using a stand pipe and trap. I don't think I can explain it clearly though if you haven't seen what I mean.

Can you post a pic of the waste pipes that you have got? What will be handy is a horizontal run after the sink trap and before it goes out through the wall or into the soil stack.


EDITED:
I bet the Plumbers know how to do it. Put a question in the "Plumbing & Central Heating" section (they don't often come in here )

Give it a "subject" title like "undersink waste backflow" so they don't think you're asking about appliances.

 

[sime10]

Bad idea to run both wastes into one I would never do it

Take a new waste to outside from the dishwasher with standpipe trap as suggested above.

 

[Heyyouitsme]

cheers for the input guys, only reason i did it that way was it was that way when i moved in. time to knock a brick out lol