correct pipes

[MasterPlumbersKeymaster]

I am installing some new pipe in my house and the existing pipe is cpvc in a crawl space is there a problem transferring the cpvc to copper and if so what is it?

[SylvanLMPParticipant]

The problems normally associated with mixing ferrous and non ferrous materials is the coefficient of expansion and contractions are very different.

Plastic piping doesn’t suffer the same effects as copper especially on hot water lines
as excessive water temperature like heating water above 140 degrees Fahrenheit
can accelerate the process of erosion/corrosion. As the temperature
increases, the velocity should be lowered.

At 180 degrees Fahrenheit, the
velocity should be down around 2 – 3 feet per second (fps).(copper)

Plastic piping does not have a problem with erosion BUT it doesn’t take pressure fluctuations as readily and water hammering from a quick closing valve will cause a plastic system to fail

Chlorinated Polyvinyl Chloride has the ability to handle temperatures of 210 degree F
working temperatures.

Under most conditions there should be no adverse mixing the materials as neither one would cause any kind of chemical reaction with the other.
Just make sure you keeping your temperature with in the normal operating range of the copper and the pressure range with in the plastic piping operating designs.

Just think about adding a few 4 fitting swings on the copper for expansion loops.

[bungieParticipant]

Dont get caught and use hemp on the joint between the copper and pvc, sound obvious but when the hemp expandeds it breaks the pvc fitting

[SylvanLMPParticipant]

Excuse me “HEMP” are youttalking about cotton Quick wwick OR lamp wick thread for threaded piping?.
I would suggest either teflon paste or teflon tape.

If someone did use hemp with pipe joint compound like Hercules pro dope or rector seal # 5 the possibility of this stuff expanding is non existent as the water would never come into contact with the internal threads of the fittings.

Teflon tape is much easier to work with and thus would be the choice I would strongly suggest.

[GuestParticipant]

I would suggest just dont use the HEMP prior to commenceing to work

[Author]

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