How much space needed behind dishwaser/washing machine....

Thanks a lot guys for the info.

So if I used one of those I would need a trap? Looks useful but maybe more so for existing installations than brand new ones?

Not sure if this "diagram" is clear - if not I'll post up a proper one.



        <No stack behind this wall>
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PipePipePipePipePipePipePipePipePipe
| Cabinet : WashingMashing : Sink :  Dishwasher
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So did I understand that ideally each appliance would have its own pipe to the stack. Since that would be hard, would I gain anything by having standpipes behind sink (for dishwasher) and washingmachine (for itself)  rather than going in at the trap under the sink ?