"Peter" wrote in message
...
I want to place the soil pipe from the back of a WC pan within the
70mm gap in a stud wall.

Is anyone aware of a manufacturer that makes a suitable pipe which
will be equivalent to a 10cm regular pipe but of an elliptical or
rectangular cross section?


In the UK the Building Regulations require that branch pipework for WC's
should be a minimum diameter of 100mm if the WC outlet is greater than 80mm
diameter, or 75.3mm if the WC outlet is less than 80mm diameter.

In reality, the smallest pipework available in the UK for WC branches is
82mm diameter. 82mm soil pipe and fittings are stocked at some plumbers'
merchants.

The reasoning behind these branch pipe dimensions it to ensure that pipes
are of an adequate size to take the discharge from the WC without blocking.
The Building Regulations Approved Document H - Drainage & Waste Disposal can
be found he -

http://tinyurl.com/2eaf5

The only real alternative to standard sized soil pipe is to use a
macerator/pump, from which the discharge pipe can be considerably smaller
(down to 22mm in some cases), however it is probably worth reading up on
others experiences with these devices. One such is here.: -

http://www.diyfaq.org.uk/humour.html

The Hepworth Plumbing Products Team
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Tel: +44 (0)1709 856 300 |Hepworth Plumbing Products
Fax: +44 (0)1709 856 301 |Edlington Lane, Edlington
Email: |Doncaster, UK
http://www.hepworthplumbing.co.uk |DN12 1BY