"cuckoo flower" wrote in message
...
On Wed, 23 Jul 2003 07:11:44 +0000 (UTC), "a0000000000"
wrote:

yes, i am using plastic pipes & fittings, and all the pipes are in
black plastic conduit, with black plastic junction boxes (with plywood
lids) where joints and exit points are. All the stuff is Hep20.

will the conduit hold it's shape under the weight of the concrete
(maybe 4 inch thick); not sure about this



The plastic pipes will expand even more than copper so will need some kind
of all round space to allow for movement. If you don't allow for them to
expand and contract then your joints will definitley just fall apart.


If you are using plastic pipes just pour concrete. Although I would put
them on a concrete base first just so they are completely enclosed. What
you have done is the normal way of construction on the continent burying
plastic cables and pipes in a concrete screed. The manufacturer of the
plastic pipes should be able to give you some guidance.

However, as everyone has pointed out do not do this with copper pipes,
they
react with concrete and expand when heated and will fail quickly.