On 27 Apr, 08:18, "Jim Alexander" wrote:
"sm_jamieson" wrote in message

...



I have fitted 450mm inspection chamber (had to be changed from 300mm
after correspondence with BCO (grrrrr).
I know about bedding the drainage runs in pea gravel etc. But what
about the chambers themselves ? A couple of related questions.

1. The plastic chamber has a hollow base formed by the underside of
the moulding, and little legs around the edge. I've left a good space
8" or so underneath to put concrete to give it a good foundation. It
is currently supported where the concrete will be, by bricks. How far
do you usually put in the concrete - just supporting the little legs,
or right up under the moulding so the whole thing is supported
underneath ?

2. How do you backfill around the chamber ? With pea gravel, or with
soil. Note that eventually a recess cover filled with paving will be
placed on top, and this will need to be supported by a good ring of
concrete around the chamber, and I can't see how this concrete can be
supported on pea gravel around the chamber.

manufacturer's installation instructions eghttp://pdf.hunterplastics.co.uk/pdf/underground/ugt7.pdfwill answer your
questions.

Jim A

Well, the floplast site (screwfix stuff) says very little. I've also
looked at marley and hunter. The approaches I have seen are backfilled
with granular fill as around the pipes, and the frame and lid
supported on concrete which in some diagrams extends enough to ensure
the
frame/lid is supported on surrounding ground rather than the backfill,
sometimes not !
Or, the whole thing incased in concrete, bottom, sides and frame/lid.
In no case have I seen what http://www.pavingexpert.com suggest, which
is a solid concrete slab underneath, and text suggesting that this is
supporting any weight on the lid transferred via the risers.
So I guess a commonsense engineering approach is required. Which
probably involves lots of concrete !

What I was really hoping was, how do folks usually do this ? Any
comments from experience ?

Simon.