I'm about to move a utility room sink and washing machine. The
existing drain for both goes into a downpipe from an upstairs toilet.
I can either extand the drains to run into the same place or use an
alternative, this raises a couple of questions:-

How can one tell where an outside drain grid goes to? Our kitchen
sink currently empties into one of these though I can't be
absolutely sure this is legitimate/allowed. If I could use a
similar one for the moved sink and washing machine it would make
for much simpler routing of the wast pipe[s].

If the above is 'not allowed' then what is the recommended minimum
slope for a sink waste? It will need to run about 3 metres
horizontally and will have a short 'zig-zag' to go around a
projection in the wall it would need to run along.

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Chris Green
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