Washing Machine & Dishwasher under-sink connection

[ookoro]

Hi

Hoping someone could help. I disconnected my dishwasher as it's being replaced. There is a washing machine also connected under the sink. I ran the washing machine without the dishwasher connected and the kitchen flooded. It also flooded when the sink was being used. I'm guessing I should have capped the spigot so this didn't happen.

My question is when the new dishwasher is reconnected, with the water from the sink and the washing machine back up into the dishwasher?

I have attached a photo which may help explain.

Thanks in advance for your help.

The new machine will or at least should stop water getting into itself.

I can't see the picture clearly enough, but the key question is where the flooding was from. Was it from the filling or the draining?

I've just looked at the photo and can see that you can't read the red writing.

The top red writing says "where washing machine waste is connected".

The bottom red writing says "Dishwasher waste hose goes here. Water currently comes out of here when washing machine is emptying or sink is in use".

Thanks

Draining of dishwashers usually involves the water being pumped out, and the water should not drain back.

The filling is shared with tap and washing machine, so, yes, it is the same water going into all three, but it's clean water.

Hi

It's from the draining.

Actually, I am a bit surprised that that doesn't have a u bend going up, that's what I have for washing machine and dishwasher waste.

Oh, how does yours look @Laira?

@outabout - So when the washing machine empties once this dishwasher is connected, the washing machine waste water won't go in the dishwasher? If the dishwasher isn't on, how does it automatically pump the water out?

a bit like this

(waste pipe goes at the top)

This isn't mine, btw, but this shows it much more clearly than the mess under my sink.

this is a clearer schematic

@laira do you have 2 sinks?

On the basis your old machine drained fine the new one should although as pointed out all machines and the sink should be going through the U trap, it appears your machine connection that joins the slanting black pipe won't have the benefit of the U trap. I suspect most machines actually have a non return valve inside or have a version of a trap built in to combat these issues.

Yes, but the pics I showed you are for one sink and one dishwasher/washing machine.

the waste hose from both appliances should curve upwards, right up to the underside of the worktop. That means water will not drain into it unless it is at such pressure that it can rise up into the sink. So turn the spigots to face upwards, and use something like a cable tie and a screw-in cup hook to support the top of the curve. This also prevents tea leaves and bacon fat fro the sink running into your washer.

You can get a stop end for your existing waste at a very modest price. It will attach with a large plastic nut. The spigots are usually delivered closed at the ends, you have to remove the bung or cut the end off before use.
www.screwfix.com/p/mcalpine-appliance-trap-white-40mm/95241

Piglet John killed the conversation
My input would be for temporary just put some plastic bag over the spigot anda couple of elastic bands, it'll do until the new machine is added.

I wonder if a prosecco cork would be large enough? This IS MN after all!
Getting the outflow pipes of machines up to the underside of the worktop is of course the obvious reason water won't backflow.

Thanks for your help everyone. I've reconnected a new dishwasher. So far so good. I'll take a picture and update.

Thanks again x

If the outlet pipe is fitted and tied up 'high' as Piglet said you will be fine.
Just tried squinting even harder at your original picture. If the dishwasher is connected to the tapered ridged bit of pipe that is facing 'backwards' and is the same height as the top of where the black pipe joins the U bend assembly then it is perfectly correct anyway so just clip the dishwasher outlet pipe up as high as it can go.
The grey pipe joining the black one part way down seems to be a red herring.