Water backing up in dishwasher

[aroominyork]

Earlier this year we changed our dishwasher. During the days after the old one had been taken out and before the new one was installed, the loose water pipe was dripping so I put a bucket under it which I emptied each day. The new dishwasher runs fine, but about a day after running it water starts collecting in the unit in the photo and over the next day or two it rises and a pool of water starts building up in the dishwasher's base. I also notice that when the dishwasher starts running, water sometimes starts coming out of the adjacent kitchen sink plughole.

I had a plumber in the house today for a different job and asked him what it might be. He was not sure what might be causing the problem, but suggested having a separate trap not connected to the sink . He suggested getting a dishwasher engineer to look at it, but I am convinced (based on no specialist knowledge at all!) that it is a plumbing issue and not a dishwasher fault.

Can someone please advise me on this? Thanks.

 

[snowhead]

I'd guess there's a partcial blockage in the waste pipe or trap from the sink to outside or wherever it goes.

 

[aroominyork]

So if the plumber pulls out the dishwasher should he be able to trace and fix it? And is a separate trap/outlet for the dishwasher, separate from the sink, a good idea?

 

[nicam49]

Does the kitchen sink, when full of water, and you pull the plug out to empty it, does it drain away nice and fast or sluggish? If sluggish then maybe the drain pipework needs dismantling and cleaning out.

 

[aroominyork]

It drains pretty well.

So where are we with this please? What else might cause water to back up into the dishwasher other than a blockage? Creating a separate outlet for the dishwasher would, I think, mean bashing a hole into the outside wal (which it is sat against) and that sounds quite a big job as an experimental solution.

Should a competent plumber be able to diagnose the fault? I was surprised he suggested getting a dishwasher expert down without looking at potential plumbing problems first.

 

[nicam49]

Sounds like the plumber had something else on his mind. I take it you had no problems with the old dishwasher draining. Perhaps the drain hose from dishwasher is kinked meaning the pump struggles to empty the machine as there's too much back pressure. The other issue of water coming up thro ' the sink is a side issue and maybe not linked to the main problem.

 

[king of pipes]

From what you've described it sounds like a partial blockage I would get some washing soda put it in your machine in a bowl , and run the hottest program through it to clean everything out before pull everything apart. Kop

 

[aroominyork]

So just sit some soda (how much?) in an upright bowl and run it, yes?

 

[king of pipes]

Yes mate a breakfast bowl size 3/4 full 👍

 

[aroominyork]

That didn't work. I ran it and afterwards poured in a little water to give it a head start and see if the level rose, which it did - there is a pool slowly forming. Next steps please...?

 

[gpbeck]

Dismantle all the drain pipes under the sink and clean them. If you get wet, the drain is blocked further along. If they're clear, warranty call for Dishwasher.

 

[aroominyork]

Does the fact that a pipe was dripping when there was no dishwasher in place suggest it is a pipe and not a dishwasher fault?

 

[king of pipes]

So let me get this right the dishwasher is filling slowly when it's in standby mode ? Is that correct ?

Does the fact that a pipe was dripping when there was no dishwasher in place suggest it is a pipe and not a dishwasher fault?

That only means the isolation valve doesn't close off totally it will not cause the issue you have as the valve would normally be open when connected

It could be the inlet valve which is opened and closed via a solenoid your plumber may have been correct in the need for a service call . Kop

 

[aroominyork]

So let me get this right the dishwasher is filling slowly when it's in standby mode ? Is that correct ?

Yes - water slowly comes up through the (trap?) shown in the photo when the dishwasher is switched off between cycles. The water collects (and starts to smell after a few days) in the base of the machine.

 

[Basher]

As per KOP post #13
Your dishwasher has a solenoid valve inside it, whose job it is to let water in when it's needed, as demanded by the timer/program, and shut it off the rest of the time.
It seems it's leaking. This is a job for a Dishwasher repair person, who would likely change the valve.
The part can cost between £10 to £50, depending on the brand. The labour charge would likely be the main cost!

Sorry, I just re-read your original post. It seems the dishwasher is pretty new. This should be a warranty repair!

You could absolutely prove it's the solenoid valve by removing the dishwasher waste pipe from the drain, and tie it up somehow (so water doesn't come out of it). If water continues to appear in the bottom of the dishwasher, it cannot be coming from the drain!! On the other hand, if it doesn't, it's a drain issue 😀

 

[steadyon]

Another possibility to consider is mains pressure. Most appliances are designed for a maximum continuous pressure of 5 bar, usually with a short period at up to 10 bar. IF this were the problem, then:
1. Excess pressure might account for:
1a. A new machine slowly filling when turned off if water is forcing its way past the solenoid valve.
1b. The old shut off valve leaking slightly when the old machine was disconnected.

To determine the incoming mains pressure it would need to be tested with a gauge, something like Screwfix 82412. This would attach to the shut off valve which was leaking with no machine connected.

If your incoming mains pressure is greater than 3 bar you could have a pressure reducing valve fitted (e.g. Screwfix 7978J) to reduce the pressure on the house side to 3 bar.

Pressure can vary during the day, depending on demand from other people. Peak pressure is likely to be in the early hours of the morning which would be the best time to measure, but if infeasible, try late evening.