"Commander Kinsey" wrote in message
newsp.0jb9g7qbwdg98l@glass...
On Sun, 19 Apr 2020 21:20:36 +0100, Rod Speed
wrote:



"Commander Kinsey" wrote in message
newsp.0jb5akq6wdg98l@glass...
On Sun, 19 Apr 2020 19:55:15 +0100, NY wrote:

"Commander Kinsey" wrote in message
newsp.0jb2xvjcwdg98l@glass...
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

It might have been to avoid sewer gases from flowing up the drain pipes
from
sinks if the water in the U trap got blown/sucked out. I'm not sure why
it
was fairly common (or even universal) for older plumbing but is very
rare
on
modern plumbing, even on houses with external drain pipes.

Perhaps the venting wasn't so good in those days? Although I don't see
why, the vent pipe sticking up to roof height has always been pretty
much
the same.

I will make a confession. When I was very little (maybe around 5 years
old)
I used to have an infatuation with plumbing, and knew various houses on
my
walk between home and school not by who lived there but by the pattern
that
the pipes made on the wall. Embarrassing to admit such nerdy behaviour!

Sounds sensible to me. When the mind is doing nothing during your walk,
it's going to think about something.

There were some houses that had steeply-sloping pipes from sink/bath
directly into the vertical soil pipe, but which had a second pipe that
branched off the sloping pipe and entered the soil pipe higher up. That
always intrigued me. I wonder if it was a way of avoiding the U-trap
water
from being sucked out.

That makes sense, a smaller version of the big pipe that's usually
placed
just after a toilet. When the sink finished emptying, the water flowing
through that steep pipe and filling it's whole diameter, would suck the
air behind it. But the extra pipe allowed air in from higher up instead
of pulling on the u-bend water.

It was even done for rainwater pipes:
https://goo.gl/maps/6zvySgaiNRRny41w5
shows the pipes from three gutters draining into a common pipe, with
two
of
them going into a hopper and another going into a side branch of the
down
pipe.

I don't see the point in that. If the downpipe became blocked, all that
does is make loads of water pour out of the box instead of just spilling
from the gutters over a wider area. I'd say it makes the problem worse.

Not really because the overflow happens in one place and can
be organised so that is never a problem. With it overflowing
the gutter wherever the gutter happens to be lower, you don't
have any real control over what it overflows onto and the lowest
point in the gutter will change over time. It wont with the box.

My gutter pours onto the postman waiting at the door.

So the box approach that doesn't get that result is better.