Minimum vertical clearance for waste plumbing under sink?

10 Feb 2007
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United Kingdom
Summary: What's the minimum vertical clearance I need (from the bottom of the main sink bowl on a 1.5 bowl sink) to accommodate waste plumbing? Washing machine and dishwasher may be connected in to sink waste.

More: Building an extension to kitchen. 1.5 bowl sink to go by window in new external wall, inset into standard 720mm height cabinet. Washing machine and dishwasher to go next to sink (one left one right, or maybe dishwasher on left and washing machine further along on same side). I want to fit a pull-out waste-separating bin in the sink cabinet which is quite high (362mm). But this would seem to leave me with only 220mm vertical clearance between bottom of main sink bowl and top of bin cover. Question: is this enough to fit a sensible waste plumbing arrangement? Current sink has washing machine and dishwasher waste plumbed into sink waste (directly underneath sink bowl) and U-bend extends to about 275mm below bottom of sink bowl. Is shortening to 220mm possible? Would plumbing in w/machine and dishwasher waste separately help, and if so what's the best arrangement? Layout of outlet pipes is relatively flexible (wall not built yet!); waste gully is around 1000mm sideways of sink on outside of wall.

Any advice will be gratefully received. I apologize if this is a very elementary question or if I've overlooked a previous forum post that answers it.
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kevplumb said:
how big is the largest clearance ?????

kevplumb, many thanks for the lightning reply. Vertical clearance with planned sink and bin is 220mm between bottom of large bowl and top of bin cover, 285mm between bottom of small bowl and top of bin cover. Hope I've understood your question. Thanks again.
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TicklyT said:
There are wastes available that connect multiple outlets to a 'manifold' mounted flat at the back of a cupboard via offset pipes from the sink outlets. They can accomodate up to five outlets (say up to 3 sinks + 2 appliances) and they need minimal clearance below the sink outlet.
TicklyT - Many thanks, that looks very useful. Incidentally, after a bit more forum reading I see that HepvO valves are often recommended where there's little space - if anybody has thoughts on whether they'd be useful here (and in what arrangement) I'd be very interested.
Thanks again.

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