TheScullster
wibbled on Wednesday 30 June 2010 12:27

Hi all

Two questions on 40mm washing m/c waste..

Does it matter how high the elbow is that takes the pipe through the wall
(or conversely how long the vertical leg is, if I raise the position of
the elbow).

Not really, with one proviso: if the elbow is too close to the top of a
standpipe, teh force of the machine emptying can cause "gurgle-back" ie
flooding out the top. Swept bends rather than elbow/knuckle bends help. I
have 12" from top of 40mm pipe to bottom of swept bend, through the wall
then another swept bend and it works fine.

With a sharp knuckle bend I'm fairly sure it would not work.


Is it usual to put a trap of some sort at the bottom of this (my current
install doesn't have one and I don't remember bad smells as a result)?

If it is plumbed into a closed sewer branch, you absolutely *must* have a
trap.

If it goes into a gulley or hopper, you'd survive without but the trap would
help reduce cold draughts in winter.

--
Tim Watts

Managers, politicians and environmentalists: Nature's carbon buffer.