Kitchen drainage - how many pipes?

2 sinks, 1 washing machine, 1 dishwasher - all going into a 4-way manifold on the soil stack.

(like this -

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could run 4 separate pipes, or 2 appliances per pipe, or some combination thereof.

I'm inclined to have each sink on a separate pipe, each with either the dishwasher or washing machine upstream of it - on the basis those appliances will sometimes pump out very hot water which will tend to shift any grease deposits in the pipe.

Any thoughts on advantages/disadvantages?

I can't see that building regs has anything to say one way or the other.

Reply to
dom
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snipped-for-privacy@gglz.com coughed up some electrons that declared:

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I've stuck one sink and two wet appliances on a single 50mm pipe running about 3m at a fairly steep gradient (roughly midway between the building regs min and max slopes for a kitchen sink).

Simulated tests with several hoses direct from a 22mm main indicated the system could stand >= 55 litres per minute sustained flow spread over each of the 3 pipes.

I did have to be a little careful with the falls from one pipe to the next as they merged otherwise I got effects like discharging into the middle pipe would back track and gurgle (not overflow) the higher first pipe.

In other words, no problem.

I designed a single 50mm U-trap to be shared between the two wet appliances, built out of solvent weld bends and tees (for clearing). The sink is the

3rd and lowest join without the U trap obviously.

You can of course get sink traps with 2 inlets for machines which is likely to be jointed to a 40mm pipe.

The advantage of sharing the main run is the machines will tend to have a good clearing effect on the pipe as you suggest.

I think your theory of 1 machine and one sink per pipe is perfectly practical.

How long is the run and do you have many corners to go round? I think it was Dave P who suggested I look at 50mm pipe between the stack and the branches and I agree - you can get a hell of a flow down that stuff and it isn't

*much* bigger than 40mm(...)

Try to use smooth bends and not hard elbows - the effect on flow and back pressure is marked (you can tell I had fun in the garden trying this!)

HTH

Tim

Reply to
Tim S

Hi Tim - thanks for the tips.

Run is straight, no bends in the horizontal plane, about 2.3m from the further sink to the stack (so the further appliance may be slightly beyond the 3m building regs maximum) - but I'm limited to 40mm pipework throughout.

Reply to
RubberBiker

RubberBiker coughed up some electrons that declared:

I don't think you'll have any problems with 2 x 40mm as you originally described.

You could either use the sink trap with an appliance spigot or run along from the sink to an open standpipe.

If the latter, I would have an extra steep fall on on the presumably short run from the standpipe to the sink junction to alleviate problems with the sink crud wandering back towards the appliance and depositing crud along the way. That's very dependent on how the tee joint is arranged - I found that under some conditions a tee can take a high flow from one or the other inlets with no back pressure and no back tracking into the other inlet - under other conditions (mostly like there being a bend right after the tee) then sometimes there was enough back pressure to do non ideal things.

Cheers

Tim

Reply to
Tim S

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