Washer water pouring into Dishwasher. What part do I need? Non return valve?

lancslass2008

Hi all

In our house I keep finding all the waste water from the Washing Machine in the bottom of the Dishwasher. On inspection I can see the problem is that the waste hose for the washer is joined to the Big thick sink waste pipe (the one that has a 'U' bend at the bottom of it) above the join where the dishwasher waste comes in. Obviously, common sense tells me the problem is caused when the washer empties, that waste water from the washing machine enters the sink waste pipe (under the sink) but then flows down the pipe that attaches to the dishwasher. There is enough room to swap the pipes around, Ie. Put the dishwasher waste higher up and the washer below that, but surely then because the dishwasher waste comes in above the washer waste I will just get the same problem, but in reverse??

So I trotted on down to the local plumbers merchants and he told me

"You need a non-return valve fitting to your sink waste pipe where the dishwasher waste joins your sink waste, but we don't do that on its own. You have to buy the full waste kit, which includes your sink waste and 'U' bend. This has 2 waste inlets built in for your washing machine & your dishwasher".

Ok, so I agreed to that. However, on showing me the kit I told him it was not the same as the existing setup. This is because We have a sink and one of them tiny sinks next to it. Sorry, I don't know what this sink is called, but I just looked on Google and I think they are called 1.5 Bowl sink with drainer, like this style.

https://www.lowcostbathrooms.com/kitchen-sinks-228614207/carron-phoenix-sinks-228614459/carron-phoenix-stainless-228614461/carron-phoenix-stainless-kitchen-11295.htm

Now he says "We don't do sink waste kits for that type sink that also have 2 waste inlets"

So, I spoke to a friend and he says he'll have a look for me later in the week, but he's sure there's a dedicated valve/part that you can buy.

Any help please?

absent_dad

I would go with your first thoughts first, as this is free

Swap over the pipes so the dishwasher is on top. There is nowhere near the same amount of water in a dishwasher as a wahingmachine. The force of the pump from the washing machine is so strong that the water isnt clearing fast enough so finding its way into the dishwasher, if the dishwasher was above the water would have to be forced up agains gravity, if this happens you may have a partial blockage in your u-bend or further down, is the sink slow to empty?

Anyway, do what is free first.

Hope this helps

ormus

you should not need any one way valves.
make sure both flexible pipes are high up before entering the pvc waste pipes.
the machines manuals should tell you what the correct minimum height is.
but generally, as high as underneath the work surface top.

otherwise use a completely seperate waste outlet for either machine.
usually the WM.

ic

Have you checked that the u-bend isn't partially blocked? It might be draining slowly which is causing it to fill - it should never really fill above the height of the bend.

lancslass2008

Hi all

Thanks for the advice. No, I have not checked the 'U' bend to see if it is Blocked. I will check this when I get home.

Thanks all