On Sun, 19 Apr 2020 21:23:47 +0100, Jim GM4DHJ ... wrote:

On 19/04/2020 21:18, Commander Kinsey wrote:
On Sun, 19 Apr 2020 20:54:44 +0100, Jim GM4DHJ ...
wrote:

On 19/04/2020 20:31, Commander Kinsey wrote:
On Sun, 19 Apr 2020 20:29:37 +0100, Jim GM4DHJ ...
wrote:

On 19/04/2020 20:20, Commander Kinsey wrote:
On Sun, 19 Apr 2020 20:12:10 +0100, Jim GM4DHJ ...
wrote:

On 19/04/2020 19:28, Commander Kinsey wrote:
Why did drainpipes used to have a box on the wall, some sort of
overflow
if blocked? See link below for an example photo.
https://www.dropbox.com/s/1jry8zas14bmivc/box.jpg?dl=0
yip hopper heads were for that function and others....usually in the
days of three pipe systems foul waste and rainwater....then again
cast
iron rainwater downpipes weren't usually cocked if they were for
rainwater only and if the drain blocked the water ****ed out of the
first joint above ground......

What's the advantage of your waste spilling all over the garden
instead
of just not leaving the bath?
what ? ...

If the pipe is blocked and you empty your bath, then if you have a box,
the water goes everywhere outside. If you have no box, the bath just
stays full and you call a plumber. The second one is preferable
obviously.

In a one pipe combined drainage system where there is no storm water
sewer and if the drain blocks underground and it is raining the water
will back up and will come up the lowest appliance the bath if the
rainwater is into the top of the SVP ....you will have a flood in the
house big time... would like to see you bailing out the bath quicker
than the water backs up into it .......the best way is to take the
rainwater down in its own downpipe to ground level and trap it off into
the combined drain with a vented trap ...then if the underground drain
blocks the rainwater will come out the trap at ground level..... two
pipe systems don't have a vented rainwater trap and the rainwater
downpipe joints are not usually cocked......to be honest hoppers were
just convenient ways of taking pipes from various beaks in the roof to
one downpipe...preferably NOT the SVP for the above reason....sorry I
didn't understand your question ...still don't but HTH ....

Good point, I hadn't thought of roof water going into the sinks and baths.
that's OK .....nobody does we always tried to discourage builders from
sticking rainwater into the top of an SVP but couldn't stop them doing
it ... we could where it was a two pipe system though.....

When did two pipe systems start being used? Because I was surprised to see sinks sharing a pipe with rainwater on a building which I don't think is all that old. Hopefully it goes into the sewer and not the rainwater drain.