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Discuss Water backing up in dishwasher in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

king of pipes

Esteemed
Plumber
Gas Engineer
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5,153
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
 
Messages
7
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.
 
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169
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 😀
 
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929
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.
 

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