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.