So, for the last couple of weeks, the dishwasher has been collecting water in the bottom of it – I know this as it isn’t being used for washing anything, but is being used to dry dishes.

Anyway, the bottom of the dishwasher has a lot of water in it – more than just the drips from the dishes. I’m guessing there is a valve of some sort between dishwasher and rest of the plumbing as it seems to fill after the sink is drained.

In the same vein as How long is a piece of string, my question is – having absolutely no knowledge of plumbing – is this valve-thing going to be rather obvious?

I’m guessing I might need to replace it, but before I do that I’m wondering if I can get it removed so I can see if the valve is broken or just needing reset.

Is it throwing up any error code when it’s doing this? Our last 2 have always thrown up an error if they don’t drain.

Last time I had this it was a small shard of glass was blocking the drain hole in the bottom, was dead simple to fix once I’d found a Youtube showing me how. Will be different for each dishwasher though so perhaps get on Youtube and search for some videos for your particular make and see what comes up. I just searched for “Miele dishwasher not draining” and there was multiple videos saying this was a common fix.

No codes as there isn’t a display and the lights that are showing haven’t changed.

We don’t use the dishwasher due to the lack of water drainage…I suspect there is a valve of some sort that isn’t closing so when the sink is filled with water and drains, it drains down the pipework but also then drains into the dishwasher. This makes me think there is an issue with the drain from dishwasher to the rest of the drainage pipework.

Another shard of glass here too!

What concerns me here is that you think the dishwasher is filling when the sink is drained. Can’t picture how this would happen.

Disconnect and check the drainage filters and the pipe if accessible. As Doug says, plenty of vids on YT for most makes.

IANAP, but what does your dishwasher empty into? We’ve had problems because ours, and our washing machine, connects into the thing under our sink that works like a U-bend. Or water trap, or whatever it’s called. So if we let too much food waste go down the sink, or if too much fluff comes out of the washing machine, the trap gets bunged up and I have to clear it out or the dishwasher and washing machine don’t empty properly.

BUT a further problem is beyond the trap. Where the pipe exits our house, it joins other waste pipes from other flats in the block. And, somewhere outside our property, if that pipe gets bunged up (if our upstairs neighbour empties their fat fryer down their kitchen sink and causes another “fatberg”!), our water can’t drain. Or, worse still, their water backs up up our kitchen waste pipe and we get their washing machine waste water flowing up into our sink!

So I’ve fitted a non-return valve in the pipe just before it leaves our property, like this:

…which means waste water can flow _out_ of our place, but not back into it.

I think washing machine and dishwasher do go in to the u-bend thing from the kitchen sink – clearly would have helped if I’d explained that the dishwasher, kitchen sink and washing machine all sit next to each other.

Might be the filler float valve, they get gunked up. I have fixed these issues by running a mega hot full intensity wash, empty, with a special dishwasher cleaning tablet.

Doesn’t sound like anything to do with the dishwasher if it is filling when you empty the sink. Assume it empties normally when the dishwasher runs a cycle (assuming you don’t empty the sink)?

I suspect they aren’t designed to stop water coming back in the inlet as there should never be any water coming that way. Pump empties the dishwasher and water runs away through gravity.

Your problem is more likely with the pipework under sink – pipework or trap probably partially blocked. Water backs up when sink is draining and spills over into the dishwasher drain?

I run the anti cal cleaning thingy on hot wash every 3 months. Starts to get a bit wiffy before, cleans trap too.

Try cleaning filters and checking obstruction.

Problem I find is continued eco washing builds up grease and grime.

There is something badly wrong with your waste water plumbing if you are getting a reverse flow from sink to dishwasher as the setup should make this impossible.

Twin appliance trap is the thingy underneath the sink.
2 spigots off the U bend that the grey waste pipe connects to.
Should be plumbed in such a way that the grey water wont run into the dw.Try mr muscles foaming drain clean solution, or just buy a new trap
Take decent photos into screw fix and buy the mcalpine one.

Checked the pipes under the sink…as said, I can’t see how the water can get up a near vertical flexible pipe into the dishwasher…will try the pipe cleaning stuff and see if that helps.
I’ll also give the pipe a bit of a wiggle and squeeze to see if I can feel any blockages.

Bet there is a blockage or restriction and the washing machine discharge is finding its way to the DW..
If you dont use it blank it off. Screw fix sell a spigot with a bung for like £2.50.
48625 is the sku

There is something badly wrong with your waste water plumbing if you are getting a reverse flow from sink to dishwasher as the setup should make this impossible.

Unless you have an anti-syphon loop that goes higher than the sink overflow then all it takes is a blocked outlet and the non-return valve in the dishwasher to pass slightly (which it will).

First thing, put a cup of caustic soda into a sink of cold water and then let that drain. That will break down anything in the waste pipe.

You can do the same in the dishwasher, as long as there are no aluminum components (there shouldn’t be, but this is why overpriced dishwasher cleaning products exist).

If cleaning it doesn’t solve the issue, then at least you’ll have clean pipes when you disassemble it.

I’d bet on the impeller of the dishwasher pump having a bit of glass or a lemon pip stopping it turning. Pull the machine out, put the outlet hose in a big bucket and run it. If it pumps out successfully into the bucket it’s not the dishwasher it’s a blocked drain.

Are you sure it’s waste water coming in?
Maybe the inlet hose is somehow leaking water into the machine even though you haven’t switched it on?

Had this and it was a small stone blocking the impeller that was stopping the water draining away.
Search for a YouTube video on how to sort this!

Most recent ‘fun’ dishwasher problem was the heat pump failing, man that was not an easy part to replace!

Another vote for the impeller – had this twice with different models/brands. Each time it was a small piece of glass, and easily fixed with a YouTube tutorial