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I'm having a problem with the waste pipe used by my washing machine. It's a standard plastic vertical pipe going into a U bend and then heading to the main drain. The problem appears to be that the flow rate out of the machine is so high it causes an air bubble to form in the pipe and then the waste water backs up the pipe and spills onto the floor.

I have fully dismantled the pipework and checked for blockages, I have used drain cleaner and I have tried testing the pipework with a hose pipe. I have only had the problem since buying a new washing machine and I think it must have a higher flow rate than the old one.

Is it possible to vent the pipe in some way? How would I do this? Should this really be necessary? Is there a simple solution? Any help really appreciated. Thanks.

pplumb,
There is something wrong with the pipework between the trap and the drain - a partial blockage is most likely. It would be unusual for the 1.5" waste pipe to connect directly with the main drain - you must track the pipework and make sure it is all clear.
Do you by any chance use Calgon in your washing machine?
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Try extending the piece of vertical pipe, and check the falls on the pipe after the trap.

htg

I can't really extend the vertical pipe as it is limited by the length of the flexible hose from the washing machine. After the trap, the pipe goes into what appears to be a width adaptor for a full width sewer pipe and then it all disappears vertically underground. I did wonder whether this sudden change in pipe width is part of the problem. I have no idea who installed it, or whether it is installed in a sensible way.

photos?

Hi Stoneyboy,
No I don't use Calgon. Is it bad stuff? Yes I know the drain system sounds unusual. The plastic pipe after the trap runs for about 6 inches then goes into a large round container which I'm sure is clipped to the top of a black vertical sewer pipe. Im sure it must be a width adaptor, unless you have a different idea? I'm also pretty sure the whole job was done by a cowboy, the same as the rest of the plumbing in the house. I'm tempted to run a new pipe and connect it to the kitchen waste instead. What do you think? Thanks for helping!

pplumb,
From your description of the problem I would say that back pressure is building in the system. If a 1.5" pipe goes into the main soil pipe within 6" and the 1.5" parts are clear I can see no other cause.
If the w/mc hose is long enough to get to the sink waste get a trap with a washing machine spigot and connect to this.
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Mmm. We appear to be assuming that it's a 40mm pipe! What if its 32?

OP - is the W/M pipe pushed right down to the bottom of the trap? If so it's in too far and the outlet/trap combination creating an obstruction and the only route the waste water has to go is upwards.

Cheers

The pipe is definitely 40mm and no, the washing machine hose is not pressed right down the pipe, it sits no more than two inches inside it.

I have now removed all the 40mm plastic pipework and fired a hosepipe directly into what appears to be a width adaptor (40mm to a wide black pipe - maybe 6" or so in diameter?). The problem definitely seems to be air related. While I had it apart, I shoved a 6ft drain snake down it, but there was no sign of a blockage. It all just sort of bubbles up and then disappears again. Think I might try one of the earlier suggestions and completely re-route the pipe to the kitchen waste.

pplumb,
From your latest post I would recommend you lift the inspection chamber (IC) covers around your home and see if you have a blockage.
ICs or an access cover should be fitted at all changes of direction of the underground pipe - don't be surprised if one has been covered.
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