Stand Pipe Overflowing

[charles.smithe]

Hi

I have a dishwasher which puts it's waste out into an open stand pipe.

This stand pipe then connects to the sink waste and flows down a long

40mm pipe across under my kitchen floor (concrete and tiled) and to an outside drain.

I have a problem in that when soapy water is drained down the sink, i can see bubbles and a small amount of water flowing out of the top of the stand pipe. I have made the stand pipe as high as possible, but the problem still happens.

I've checked for any blockages, and tried clearing the pipe just to be sure with Caustic soda etc.

I'm pretty sure that because the fall of the waste pipe isn't that big, water is favouring the easiest route and partially going out of the stand pipe.

Is there any way that I can seal the top of the stand pipe that the dishwasher outputs into, or does anyone else have a suggestion that will save me having to dig up the concreted kitchen floor! Many thanks

Charles

[Ric]

How close is the sink to the dishwasher? You can get traps that have a spurr coming off them for attaching washing machines/dishwashers. If the waste pipe from the dishwasher will reach then this would be one solution - you could do away with the standpipe altogether then.

[Lobster]

Well years ago I once had a similar problem (nasty niffs emanating from the standpipe notwithstanding a trap), and solved it as follows; however I'm not convinced it's necessarily 'correct' and someone else here may tell you valid reasons why not to do it (eg messing up the washing machine?) - if so I'm not arguing! Anyway...

I introduced an in-line air-admittance valve into the rubber waste hose (you can easily get these from B&Q etc), close to the top of the loop, ie just before the waste pipe entered the top of the standpipe. These gizmos let air in (to prevent vaccuums in the waste pipe) but don't allow water or air out. I then just bound up the top of the standpipe and rubber waste pipe with loads of duck tape, sealing the gap. Worked fine for me as it was just gas, not liquid, coming out. Not pretty, but hey...

The valve certainly worked, as you could hear it wheezing when the machine emptied.

David

[Set Square]

At what level does the standpipe connect into the sink waste? Is it at trap level?

If so, you need to change the pipework so that the sink and standpipe outlets are tee'd together (preferably with a Y-type connection) as close to the floor as you can get.

*Don't* seal the washing machine to standpipe joint - it needs to be vented.

[Dave Liquorice]

It will until you get the top of the stand pipe above the water level in the sink...

However it shouldn't do this, and indicates a restriction in the pipework somewhere. That long length of 40mm is the most likely place, we have a similar bit of pipe that is prone to becoming restricted along it's entire length.

What else drains down this pipe? Hopefully never any fat. Clothes washing powder is 90% "filler" to bulk it up, this stuff has a nasty habbit of forming a white crumbly gunk inside long waste pipes. Mechanical removal is the only real solution, but start from the bottom not the top as bits will break off an block the pipe further down if you do.

[The Natural Philosopher]

Thats a neat trick which I may copy. I ahev a simialar situation in the utility room, where a sink waste and standpipe come together.

[charles.smithe]

Thanks for your reply - it makes sense all of a sudden.

Thanks for the tip - I'll go out tomorrow to my local plumbing merchant and buy one of these.

Charles

[charles.smithe]

Hi

I thought the same too, but after rodding (using the small flexible metal pipes from b&q for unblocking drains), and caustic soda'ing 3 times, and then using one shot drain cleaner, I am pretty sure that it's not blocked.

Only thing I can think of is that the 40mm pipe could be partially crushed under the concrete somewhere. The flow coming out of the drain end, isn't bad at all, and if I flush just water down the sink, it's ok (doesnt come up the stand pipe). It's only when bubbles are in it - ie after washing up, that the bubbles rush out of the stand pipe.

I am going to try this:

should do the trick. Fingers crossed- thanks for your advice tho.

Charles