Plumbing q, washing machine floods the floor when it drains

[MuddyWellyNelly]

Our washing machine and dishwasher are plumbed in side by side in our utility room. No sink. They were re-done by a plumber after we'd had an (unrelated) leak and he changed how they were plumbed, said it had to be this way. It's been fine for a good couple of years until fairly recently. Now, anytime the wm empties, water just shoots onto the floor.

Basically coming in from the waste pipe outside, there is a short length of pipe down to a u-bend, being the lowest point. Then an upstand with one spigot, to which the wm is directly connected with jubilee clip. This is higher than the point at which the waste goes through the wall. The dishwasher hose then just rests into the open end at the top of this pipe. When the washing machine drains, instead of water going down and out the waste pipe, it's going up and pouring out of the open top all over the floor. I doubt anything is going out the drain. We've taken off the U-bend to check it's not blocked. We've rodded the pipe as best we can. We've tried taking the dishwasher hose out, or further up, to ensure it's not creating a blockage. We don't run them both at the same time. Nothing so far has helped. I guess the drain could be blocked further along, but it's an immediate gush of water up the way, not a gradual one. And as far as we can tell it's ok with the dishwasher. The dw probably empties much less water at a time so presume it's a pressure/volume issue? It's just odd that it's suddenly started doing it.

My very basic understanding would be the water will choose the easiest path so finds going up easier than around the u-bend. But again not clear on what could have changed to make this so. Is our set up correct? Why would the top be open (where the dishwasher hose rests). Would it be better being sealed or do you need the air? We may as well just let the hose rest on the floor for all the good the waste pipe is doing! Any suggestions? I'm 30 weeks pregnant so beginning to panic about the amount of washing we are going to need to do. .

as the fault has developed over time, it is not likely to be a design fault.

It is most likely a blockage.

A stand-pipe is supposed to be open at the top.

It is possible that a pipe has slipped out of place if not well-supported.

You could try tipping Washing Soda crystals into the standpipe, followed by just enough hot water to moisten them, then leaving overnight. This will help if it is an accumulation of soap powder sludge, but not if it is shredded sock fluff or a mouse nest.

You could get a plumber's snake to poke down the pipe. It would be useful to poke from the other end as well, after it has gone through the wall.

A photo might give more ideas.

Here's a pic. Best I can do between the two of them! It was a snake we used (sorry that's why I meant when I said we'd rodded it). OH has had pipes off twice now and hasn't found anything. If it's a blockage though, wouldn't the dishwasher back up too?

Very grateful for your help! . We can certainly out the snake down it again. By washing soda do You mean soda crystals?

the standpipe is not as tall as I would like, but looks OK.

If the washing machine is the lower connection, it will allow any water pumped out of the dishwasher to run into the washing machine in the event of a blockage, which might explain why the dishwasher does not visibly overflow. In this case, if you turn the washer drum by hand, you may hear water splashing, or it may steam after you have run the dishwasher. The waste hose from the washer needs to be looped up, with the top of the loop at worktop height.

On the other side of that wall, the white waste pipe probably connects to a grey soil pipe, or into a brown yard gully. Have a look at that. Is there any emulsified grease, or leaves?

I think the dishwasher pipe was looped up, but it's been pulled in and out a few times recently and perhaps wasn't put back. It does sit on an upturned plastic U which maybe doesn't show in the picture that well? Standpipe is as high as it can be due to work top.

Outside, there is an old clay downpipe (black, though painted that colour of course) that disappears straight into the ground. It just drains this waste (ie from the outside it's only a couple of feet tall), nothing else. It has a cap on it so nothing should have fallen into it. On the ground there are a lot of beech nuts around the base of it, but as far as I can tell the pipe is sealed and runs to the "junction box" (for want of a better word) at the back of the house where other soil pipes meet. I can certainly move the tree debris away just in case. There's no gully or trap or opening that I can see though. The rest of our drains are fine so I don't think it's a major blockage. We have a septic tank so always a concern! We could try taking the top off the downpipe to see whether it's clogged with dishwasher debris.

When I put the dishwasher on later I will look out for steam or any indication the water isn't draining away. Sigh, old houses are never without their challenges.

Thanks again for the help. It certainly sounds like there must be a blockage somewhere. I think when OH is back, we will try disconnecting the pipe that leaves the house and put a length of hose down and see if the water drains freely from that point.

Take the dishwasher pipe out and pour water down - it should go down rapidly - it sounds like it isn't draining away fast enough...
I had a similar problem with mine in this house flooding on emptying washing machine (first happened only when I emptied the sink at the same time - they were connected -then got to every time) - WM do suddenly dump a lot of water -so a first indicator of a problem
My problem was the drain pipe outside - 4inch cast iron had furred up and also years worth of grease etc - it was truly vile. The diameter water could get through was less than 30mm (waste pipes are usually 32 or 40mm ) - the rest was nasty black slimy yuk. And I did try and clear the blockage a few times with a snake and it got through relatively easily...
And house was only 40-50 yrs old. I had to have the pipe dug out and replaced with plastic.
But having said that - I did also have a problem a few years later - with the gutter down pipe overflowing - it was a sealed thing (no grid) into clay pipe and it was completely blocked up with 'soil' under ground - it ran into a main drain shared with 4 neighbours which my kitchen/washing machine drain also ran into a little further down.
They found the main shared drain was more or less completely blocked further down ...with pebbles (another neighbour commented how he remembered his son and the boy who used to live in my house used to 'post' pebbles into an inspection grid - ha ....wasn't that funny! ) I think the water from my neighbour and I was backing up - first pipe effected was my kitchen one , then my gutter - only thing that stopped us having a problem sooner was the sheer volume of the shared drains.
I now think the fact the water taking longer to drain out the pipe made it fur up faster...so if that is the case might be worth checking 'further downstream' is also clear...to prevent future problems.

The other thing it could be if it is clay it could have cracked/collapsed a bit or a tree root could have grown through it ...

Well OH took everything apart again yesterday. Absolutely no blockage in any of the white pipe inside the house. Then went outside and took the top off the downpipe (which is of course cast iron, not clay) and couldn't see anything. He got the hose and ran water down the pipe for at least 5 minutes and nothing came back up. He used the snake back in the way (once the internal pipes were re-connected) and it came out the other end clear. So no evidence of blockage or greasing up or dirt at all.

We looked at the setup again and decided that the hose from the wm was actually on an uphill angle. So we've played around with the attachments a little bit, and tilted it so the wm hose now obviously has a downward slant towards the u-bend. Ran the WM tonight and annoyingly fell asleep, but looking around the pipework and floor, can't see any evidence of water, and it's normally saturated.

So time will tell, but this may have solved the problem. Probably too easy to be the solution, but it looks promising. Thanks for advice :)