How to fix dishwasher standing water issues?

Question

Hoping for some assistance, I've been having ongoing issues with standing water returning to dishwasher (have fairly recently moved into house). It has no problem draining the sump, however after regular usage of the sink, water begins to accumulate in the bottom of dishwasher and smell.

On the dishwasher I've ensured the drainage works properly, replaced the non return valve on the dishwasher, isolated the water inlet to check for leakage and installed a high loop on the hose.

For the sink, it drains properly/quickly, I've ran a drain auger through the wall drain and no issues.

I'm thinking it could be the design of the plumbing and the fact that the wall drain outlet is positioned fairly high (higher than the dishwasher drain spigot) that is potentially creating issues and causing backflow into the dishwasher.

Any tips/guidance would be great as I'm trying to avoid a plumber/technician unless absolutely necessary.

Thanks!

TedBear · Answer

Hi @ct94, I think Dave's suggested test using a bucket to isolate the dishwasher from the sink outlet is a great idea to start with. The other test you could do to check if the water is coming from the sink or not, would be to put some water into the sink and add some coloured cordial to the water. Then let it out to see if it is definitely following back into the dishwasher. The question of "why" will still remain though. Your idea that the water has a better path back down into the dishwasher than into the drain, where it should go, sounds likely.

One problem I had was caused by some thin string getting into the impeller and preventing it from turning. This meant that the pump couldn't throw all the water up and out of the pipe, so it then siphoned back into the dishwasher sump. To clear it meant (with power off) removing the first filter, then undoing a plastic clip that held the impeller filter in place so I could reach in and get the string out with tweezers. A messy process, but it fixed the problem. I used my phone's camera to see what I was working on at times.

Dave-1 · Answer

Good Morning @ct94

Mmmm the only dishwasher I have is "me" :) And as @JacobZ has said you have stepped through the most obvious checks.

Maybe you could have a look online at any FAQ's about your model of dishwasher or general discussions?

You could always run the dishwasher through its cycle and then disconnect the hose and put it into a bucket of water with the level clearly marked. keep the bucket at the same height as your sink and see if there is any drawback into the dishwasher at the start of a cycle? try a few different scenarios to see if you can replicate the issue without being connected to the waste pipe.

Dave

JacobZ · Answer

Hi @ct94,

Welcome to the Bunnings Workshop community, it is wonderful to have you with us.

It seems like you've already worked through most of the things I would normally suggest checking yourself. The only other thing I can think to check before contacting a plumber or technician is the filters in your dishwasher if it has any.

If you've cleaned the filters and accessible areas, checked the drain hose for kinks or obvious blockages and confirmed the sink itself is draining freely, there unfortunately isn't a great deal more I can recommend investigating yourself.

At that point, the issue could be with the plumbing connection or waste pipe, or alternatively something within the dishwasher itself such as the drain pump. If the water appears to be backing up from the sink waste into the dishwasher, I'd start with a licensed plumber. If the plumbing is confirmed to be clear and correctly configured, then it would be worth contacting the dishwasher manufacturer or an appliance repair technician.

It sounds like you've done a pretty thorough job of eliminating the straightforward causes already, so I think getting someone out to inspect it would be the sensible next step.

Allow me to tag some helpful members for their thoughts - @Noyade, @Dave-1, @TedBear.

Jacob