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Problem With Dishwasher and Washing Machine Connected to the Same Waste Pipe

Postby pasiak16 » Sun May 05, 2019 10:39 am

Hello everyone,

I'll send links to pictures of my plumbing under the sink as pics are too big to upload here. Hope that's okay.

I have connected both dishawasher and washing machine to the same waste nozzle on the undersink trap. There's only one there and I couldn't find any proper divider hence I divided it in a different way. I know it looks ridiculous but I'm not a plumber and was trying to do the job at lowest cost possible...

Basically, my issue is that dishwasher constantly pumps waste water into the washing machine instead of straight into the drain pipe. It doesn't make any sense to me as everything is perfectly fine in the other way, meaning that washing machine pumps out the waste water under quite proper pressure straight into drainage, nothing seems to be going to the dishwasher. When WM pumps out the waste water I can clearly hear sound of water coming out of sink (sound) but when DW pumps water out then it's quiet as everything goes to the WM... That's really weird as both waste pipes from DW and WM come from the top so my guess would be that gravity itself should prevent situations like that! Why would water choose to go vertically upwards rather than horizontally?!
Waste pipes from both appliances are connected to that Y shaped divider which goes further to a flexible/collapsible pipe which then goes straight to the waste nozzle on the trap.
In my humble opinion considering the gravity ascpects and the fact that the collapsible pipe lies a bit above the sink's nozzle then everything should be fine! But it's not...

Funny thing is that I recently exchanged a DW and that's when it started, the previous one wasn't pumping water into WM, and everything was connected in pretty much the same way...

Please, can you advise something ?
Either how to set it up or maybe what elements to buy to divide the waste nozzle in some better way? I couldn't find anything sensible online...

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Simply Build It

Postby collectors » Mon May 06, 2019 9:41 am

You need a different trap like this one [url][/url]
You can get them where the trap is on a telescopic pipe that makes fitting a lot quicker as its very flexible when replacing an old one, but couldn't find it.
Should only take 1 hour max for a DIY'er.
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