flexible pipe under subfloor

Pronouncedeyen · Oct 2, 2009

I have a 1/2" flexible copper pipe (type L) coming out of a chunk of concrete and the top of that pipe is about 1/16" above where a plywood subfloor will be laid and meet the concrete.

Is it OK if the floor rests on the pipe? Or will it cause problems to have half of the pipe embedded in concrete and the other half weighted down by concrete/backerboard/tile because of the difference in expansion between wood and concrete?

hj · Oct 2, 2009

copper

The copper should NOT be "weighted down" by ANYTHING. There should be a space between it and the wood, AND the concrete. The different expansion rates may cause problems but it will not be with the copper tubing.

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Pronouncedeyen · Oct 2, 2009

hj: the pipes (supply & drain) were buried in 4" of concrete when the previous owners did the bathroom in the 1950s. I guess I'll try to bend the pipe down so it doesn't hit the subfloor.

Jimbo · Oct 2, 2009

Copper should never be in direct contact with concrete'

Pronouncedeyen · Oct 2, 2009

jimbo: really? Gheez. The people who did this bathroom back in the 1950s buried copper pipes, both supply and drain, in 4" of concrete! Not only that they buried a ton of knob and tube wiring in it as well.

Shacko · Oct 2, 2009

pronouncedeyen said:
jimbo: really? Gheez. The people who did this bathroom back in the 1950s buried copper pipes, both supply and drain, in 4" of concrete! Not only that they buried a ton of knob and tube wiring in it as well.

If that is not a joke about the knob and tube you have a major safety problem if that is still active!!

Gary Swart · Oct 2, 2009

There are frequent posts regarding leaks in slabs where copper water lines have been buried in concrete. The problem is concrete attacks the copper. It is stupid to encase copper in concrete, but it has been common practice in slab built homes for years.

Pronouncedeyen · Oct 5, 2009

shacko said:
If that is not a joke about the knob and tube you have a major safety problem if that is still active!!

shacko: Are you saying the existence of knob and tube is a safety hazard or that it was buried in concrete?

Frenchie · Oct 5, 2009

K&T is supposed to be open air, so it can keep cool... bury it, it can heat up & start a fire. Often a concern when retrofitting insulation in old houses.

Concrete doesn't corrode copper, but it might as well - the difference in expansion rates abrades the pipe. Eventually it will leak.

hj · Oct 6, 2009

concrete

I cannot imagine ANY sane person direct burying ANY wiring under a concrete slab. Concrete does not "abrade" tubing passing through it because it is held rigidly and cannot move. Expansion/contraction WILL abrade tubing which has a rock pressed against it under the concrete, however. Trying to bend a short section of copper tubing will almost ALWAYS kink it.

flexible pipe under subfloor

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