Dishwasher and Washing Machine on same tap and same outflow

[Dave]

Hi;

I've presently got my washing machine attached to a water supply in my washroom. It outflows into a down pipe which, for reasons that are beyond me, starts about three feet above floor level.

I've just picked up a countertop dishwasher whoch I'm going to stand on top of the washing machine.

I want both machines to run off the same (cold) water supply, and both to output to the same outflow. They both use standard in and out hoses. Can anyone advise me what I should be asking for?

Thanks

Dave

[BigWallop]

Hi Dave,

When you drop the waste outlet from the washing machine below a certain level the water will actually siphon out of the machine. That's why an outlet must be set at the height the manufacturer states for their machines, but a rule of thumb for plumbers is to keep the top of the soil pipe at a height of 600 mm to 700 mm above floor level. The same thing will happen with your dishwasher, so you'll need to extend the soil pipe up the wall to about a level usually half way up the height of the dishwasher.

If you have a horizontal section on the main soil pipe, then it will be possible to TEE into it and take another piece of pipe up the wall to another machine trap. But this can cause problems if the soil pipe gets a bit choked, as the water from the dishwasher will blow back with some force up the washing machine trap. So make sure you keep the pipe clean and clear, and that there is a good running angle on it. Other than that, it is OK for you to do the job the way you suggest.

[Paul C. Dickie]

In article , Dave writes

Trouble.

HTH.

[Dave]

Thanks, BW - definitely some food for thought there. But as far as counter-top dishwashers were concerned, I thought they were designed to stand on a surface, with the outflow pipe stuck down a sink; i.e. at a lower level than the washer itself; so I didn't think syphoning would be a problem. I'll see what the manufacturer has to say (it's one of those el-cheapo jobs from Safeway, made by NAIKO)

Dave

[Benjamin Aldred]

Hee Hee !!! Yeah Right. :-))

[Dave Plowman]

There is no valve or whatever connected to the waste on a washing machine, so the outlet has to be above the level of water inside it when it's in operation. A simple pump overcomes this 'head' when emptying. The reason for this simple arrangement is that if you have any sort of failure the machine may be emptied by simply lowering the pipe below the water level into a suitable container.