dishwasher and washing machine common pipework

[sparkspark]

Hi, a conundrum for you.

Currently I have a washing machine which drains into a high level standpipe and trap, 32mm which goes about 2metres to an outside drain. Now, I want to add a dishwasher to this arrangement. Uprating the diameter of the pipework is the first obvious point. But can I get away with using another standpipe for the dishwasher, or could I use a spigot? There is no air break with a spigot plumbed direct in to pipework, like with the normal undersink arrangement.

On the one hand I don't want to overload the pipework if both appliances drain at once, but on the other hand, using spigots introduces the risk of potential siphoning. Would a non return flap valve in the spigot be adequate protection? And/ or an anti syphon device, ball bearing type? Any advice gratefully received.

 

[solutions]

I would use one of these as it maintains an air gap but uses your existing standpipe to connect both appliances.
Mcalpine v33wm twin discharge standpipe connector http://www.plumbcenter.co.uk/wcssto...roof-pdp-w/std.lang.all/23/05/F42305_wpdp.jpg

 

[kris]

Washing machine should be min 40 mm pipework as stated in part H building regs so to have the 2 into it I'd defo increase pipe size .

 

[Reg Man]

Best way is to run them separate. 1 1/2" waste for each. Of course you can use all those tapping's into the waste system, but they generally cause nothing but long term problems.