Dishwasher suddenly not draining past the u-bend

[Fullpint]

Hi - First time poster, hope you can help.

My dishwasher has been in place for about two years and has not had a problem until a few days ago, when I found the dishes in the cupboard full of water.

I emptied the cupboard and turned the dishwasher on, expecting a leak in the hose or the drain pipe. But no - water was gushing out of the grey polypipe and shooting up past the inserted hose.

I checked the u-bend and it's clear. I put a drain snake down and got about 4m in, all ok.

If I take the U-bend off (all the white stuff in the image) and put the dishwasher drain in the end of the grey pipe, it all works fine.

As soon as I put the u-bend back on, water gushes up again. It's like the pump is pumping too hard and the water hits the u-bend too fast and shoots back up.

The pipe is definitely clear as I have poured water in and it never backs up. Not sure what to do now. Thanks for any help.

Image:
Imgur

https://*********/a/0sTaR72 Imgur

 

[rpm]

Edited.

 

[rpm]

Surprised that has worked tbh. Something has changed if you say it worked ok for two years so put thinking cap on.

 

[Fullpint]

Surprised that has worked tbh. Something has changed if you say it worked ok for two years so put thinking cap on.

It's actually worked for 7 years. New dishwasher 2 years ago. What is surprising about that set up? It was like that when I moved in.

 

[rpm]

It's actually worked for 7 years. New dishwasher 2 years ago. What is surprising about that set up? It was like that when I moved in.

https://www.googleadservices.com/pa...hUKEwirl6fOif_dAhUJCcAKHYvdBxIQ9aACCEE&adurl=
Spot the difference?

 

[Fullpint]

https://www.googleadservices.com/pa...hUKEwirl6fOif_dAhUJCcAKHYvdBxIQ9aACCEE&adurl=
Spot the difference?

Not really no, as it's worked for 5 years and then 2 years.

 

[rpm]

Not really no, as it's worked for 5 years and then 2 years.

Have you taken all the White stuff (your words) apart?

 

[Fullpint]

Have you taken all the White stuff (your words) apart?

Yep, and it is totally clear.

 

[Sharp Point]

There could be a few reasons why it’s not working.

The drainage pipe from the washer could be full of gunk round the inside of the pipe, this could cause the velocity of the water to speed up and hit the bottom of the u bend and bounce out. The trap could be on a run that has a air admittance valve and that’s stuck and causing a pressure build up in the waste pipes and not allowing the water to flow. The pump could on its way out and for some unknown reason running to fast. There’s still a blockage in the main pipe, yes you said you put a snake down.... but it could’ve slipped down through the 15mm orifice that’s left through it, from hard baked fat/ grease/ soap build up.

Take your pick, it’s one of those

 

[rpm]

Yep, and it is totally clear.

Good, do you know what a manhole looks like? On the understanding that even if you don`t St. Google will show you I suggest you go and lift yours. 😉

 

[rpm]

There could be a few reasons why it’s not working.

The drainage pipe from the washer could be full of gunk round the inside of the pipe, this could cause the velocity of the water to speed up and hit the bottom of the u bend and bounce out. The trap could be on a run that has a air admittance valve and that’s stuck and causing a pressure build up in the waste pipes and not allowing the water to flow. The pump could on its way out and for some unknown reason running to fast. There’s still a blockage in the main pipe, yes you said you put a snake down.. but it could’ve slipped down through the 15mm orifice that’s left through it, from hard baked fat/ grease/ soap build up.

Take your pick, it’s one of those

Pump running too fast ? Don`t think they are variable speed. 😉

 

[Fullpint]

There could be a few reasons why it’s not working.

The drainage pipe from the washer could be full of gunk round the inside of the pipe, this could cause the velocity of the water to speed up and hit the bottom of the u bend and bounce out. The trap could be on a run that has a air admittance valve and that’s stuck and causing a pressure build up in the waste pipes and not allowing the water to flow. The pump could on its way out and for some unknown reason running to fast. There’s still a blockage in the main pipe, yes you said you put a snake down.. but it could’ve slipped down through the 15mm orifice that’s left through it, from hard baked fat/ grease/ soap build up.

Take your pick, it’s one of those

Thanks, yeah I know you're right. It's got to be one of those.

The weird thing is it all works fine if I remove the u-bend and hold the washer drain pipe in the grey down pipe.

Would you recommend putting the snake into the washer drain pipe?!

 

[Sharp Point]

Pump running too fast ? Don`t think they are variable speed. 😉

If they’re a lower voltage than 240 and the board is failing, there is a possibility of them running faster due to over voltage

 

[Fullpint]

Good, do you know what a manhole looks like? On the understanding that even if you don`t St. Google will show you I suggest you go and lift yours. 😉

I'm on the 7th floor, so if my manhole was blocked there would be bigger problems!

 

[Sharp Point]

How old is the building

 

[Fullpint]

How old is the building

25 years or so

 

[Sharp Point]

Is the main stack( about 4” in diameter) plastic or cast iron?

 

[rpm]

If they’re a lower voltage than 240 and the board is failing, there is a possibility of them running faster due to over voltage

You sure about that?

 

[Fullpint]

Is the main stack( about 4” in diameter) plastic or cast iron?

Iron

 

[Sharp Point]

You sure about that?

No, not at all.