I'm hoping some one can help with my question regarding Pex plumbing (AKA Zurn Pex).

I have recently run Zurn Pex throughout my renovated home for use in baseboard heating. The pex is used for supply and return and traditional copper baseboard will be installed as the heating element. The plan is to run the Pex up to where the baseboard is to be installed and then connect it to a piece of 3/4 copper (approx 6" long) using a Pex to copper fitting. This process would be repeated wherever a stub-out is needed. These small intermediary pieces of copper would run up through the floor and eventually connect to a 90 degree elbo which would be sweated onto the heating element. So far all my sweating is done prior to connecting to the Pex. My question is, now that the Pex is connected and is in some cases within 6" of where I am sweating my elbos, will the Pex melt from the heat? If so, does anyone have any ideas on how to prevent this, essentially how to keep the copper near the Pex cool?

You can find a variety of cooling materials at your local plumbing wholesaler.

Six inches is pushing it, but as Darrel suggested, there are a number of products available at your local plumbing supply house.

If you strike out there, you can also wrap the pex with a wet rag -- A *VERY* wet rag.

I do PEX to copper transitions all the time, but I try to have all of my copper joints soldered before making the PEX connection.

If you run into trouble with this, you can also cut the PEX back and then add a pex coupling.

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Originally Posted by darrel1953

You can find a variety of cooling materials at your local plumbing wholesaler.

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Darrel1953, thanks for your help - can you tell me what I am asking for, e.g. cooling material for soldering? Are there name brands or and industry phrase I should be using?

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Originally Posted by iamgrowler

Six inches is pushing it, but as Darrel suggested, there are a number of products available at your local plumbing supply house.

If you strike out there, you can also wrap the pex with a wet rag -- A *VERY* wet rag.

I do PEX to copper transitions all the time, but I try to have all of my copper joints soldered before making the PEX connection.

If you run into trouble with this, you can also cut the PEX back and then add a pex coupling.

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iamgrowler - thanks for your help, as I asked darrel1953 are there any name brand products I should be asking for or an industry phrse I should be using?

Also, when you mention the pex coupling, I am assuming you are talking about removing the pex if it becomes damaged in the process, correct?

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Originally Posted by jdesotle

iamgrowler - thanks for your help, as I asked darrel1953 are there any name brand products I should be asking for or an industry phrse I should be using?

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I've seen them on the shelves at the supply houses, but I cannot remember any specific brand or trade name.

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Also, when you mention the pex coupling, I am assuming you are talking about removing the pex if it becomes damaged in the process, correct?

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I am.

PEX is a great product, as is copper, but mating the two requires that the copper portion of the assembly be done first.

Sweating copper pipe and fittings causes convective currents, which are drawn deep into the copper tube, and 6 inches of copper, no matter what the size, isn't much of a margin.

OTOH, one of the benefits of PEX tubing is it's remarkable memory, which allows it to return to it's original form when heated, the drawback to this memory/heat ratio is that too much heat causes the PEX molecules to dissipate, leaving you with a weakened product.

If this were a project I inherited after the fact, I would cut a portion of the PEX out before sweating the copper joints, and then couple PEX back in after the soldered joints had cooled.

What size pex tube should I run to replace a 3/4" copper pipe