Well OK then does anyone have experience of a Turbomax that turns the burner on in the middle of the night when there is no demand for heat but the pump does not appear to run?
Ok, so if there is a block on a single stack serving two different levels BEFORE the manhole junction it will flood the lower of them, if the same block occurs the other stack is unnaffected. That is all i was trying to say.
Well if this is being supervised by Building Control they will ask for a drains test which involves plugging at the manhole and flushing the toilet upstairs, heh presto water all over the downstairs loo floor. The upstairs one should hold the 6 Litres for a period, this will not happen in this case.
According to our local Building Inspector, If the existing stack that serves lower floors you should not join into it but drop a new waste down to the nearest manhole. If you were to have a block between the manhole and lower floor when you flush the upstairs one it will surface in the lower pan...