Soil fall angle

[Mark Begbie]

I will be moving various bits of soil piping around and have drawn a blank on fall rates. From a look, old cast iron pipes look to have a generally steeper fall than modern (smooth) plastic piping [which makes sense]. Also, soil piping seems to come with either 2.5 degree or 22.5 degree branch adaptors. What are the regs / practice? Is it

2.5 degrees for plastic and 22.5 for iron?

Thanks,

Mark

[in2minds]

I looked this up the other day and found reference to it being from 1:40 to 1:80

LJ

[Jonathan Pearson]

The figures 18 - 90mm fall per metre run come to mind - going down to 9mm if you have more than 1 bog connected?, which going back to the original question means that 22.5 deg is too steep

Jon

[John Rumm]

IIRC building regs say the fall should be between 18 and 90mm per meter.

Have a look at approved document H:

[Set Square]

That's between 1 and 5 degrees in real money!

[Rick Dipper]

Thats is, if its too steep the water runs away, and the solids have no water to travel with.

1 in 0 (vertical) is also allowed.

Rick

[The Natural Philosopher]

I had 1:60 to 1:110 s being in te range for outside work.

I'd say that 1:60 lies within all our estimates,so should be adopted.

[The Natural Philosopher]

or 1:11 to 1:50 in ratios

[Nigel M]

All "90 degree" fittings are 87.5 degrees to allow for a fall. The required fall depends on a lot of things (content, number of inlets etc)

Have a look at the Osma/Wavin site, in particular: