Waste to which external pipe?

13 Sep 2009
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United Kingdom
I shortly need to plumb in the whole bathroom and kitchen area. Is it ok to send shower/sink waste into soil stack(will be new stack)) and bath waste into normal downpipe (as before)? Similarly the washing machine/kitchen sink waste into soil pipe. Does it really matter which waste goes to which external pipe or can i go for the most convenient and nearest? Also the bathroom sink waste will need to go under the floor boards - is this ok?
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Can go into either pipe providing the pipe discharges into the foul sewer, not a storm drain.

Older properties have a 'combined' system where all water goes into the sewer. Newer buildings are required to have separate systems, rainwater and run off from roofs, paved areas etc goes into storm drain, toilets, sinks etc into the foul sewer.
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House is 1930's so presumably in this instance i can go for either soil pipe or normal down pipe? Just my neighbour said washing machine waste and bath waste should be going to soil pipe although they are closest to normal down pipe..
rather than guess, you ought to open a cover and get someone to run water down first one pipe, then the other.

maybe the rainwater goes to a soakaway or stream, you won't know until you check.

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