Replacing copper with PEX

[Greg Gorman]

I have a split level ranch with cast iron baseboard heat. I am replacing the original copper pipes because when home was built in 1957 the copper was hanging to low in the garage for some reason.
Can I just replace all of the copper pipes with PEX and place T's and follow the same exact route of the original copper supply?
Thanks

 

[Gary Swart]

PEX has a place in plumbing, but to replace copper is not one of them. If there are some pipes that need to be relocated, just move them. Copper is still the best pipe.

 

[Sponsor]

 

[hj]

You can do it anyway you want to.

 

[Greg Gorman]

You can do it anyway you want to.

Someone said the flow to radiators would be affected by the T connections. Is this true?

 

[Houptee]

The PEX should be oxygen barrier made for radiant heating because dissolved oxygen can pass thru regular PEX and over time damage the cast iron in the system. Also if there are Tees in your system now they are most likely Monoflo/Venturi Tees on the inlet side for each radiator, they have an internal diverter scoop inside, so you need to keep them in the same locations. You could solder PEX male adapters onto them and reuse them since they are kinda pricey.

 

[Greg Gorman]

The PEX should be oxygen barrier made for radiant heating because dissolved oxygen can pass thru regular PEX and over time damage the cast iron in the system. Also if there are Tees in your system now they are most likely Monoflo/Venturi Tees on the inlet side for each radiator, they have an internal diverter scoop inside, so you need to keep them in the same locations. You could solder PEX male adapters onto them and reuse them since they are kinda pricey.

All of the copper has already been removed. Can the scoops you are referring to be taken off the copper and reused? If not what is the best way to do it?
Thanks

 

[Houptee]

Maybe you didn't have any monoflo tees in old layout but you have to look at the ones you removed see if internally they have a scoop. If you saved the original Tees just sweat pex male adapters onto the old monoflo tees basically making them pex tees. On most main loop piping systems each rad has one monoflo tee on the inlet side then the outlet that ties it back into the main loop is a regular Tee. They are designed to divert some of the hot water into the rad then continue to next rad to keep the water temp similar for each rad on the loop. The other idea you could do is use a Pex radiant manifold and run 1/2" pex supply and return tubing for each rad from the supply and return manifold. This gives you the ability to balance each rad and also turn off each rad independently if there was a leak and still have heat working in the house to the other rads.

 

[hj]

When you said you were replacing the copper piping, you did not specify it was for the heating system. The flow to the radiators will be affected by the smaller i.d. of the PEX, and the restriction from the insert fittings. Is this a system with a main and branches to the radiators or one with a loop from one radiator to the next? You CANNOT just "place tees" where the original ones were unless they are the same kind of tees.

 

[BMWpowere36m3]

I'm remodeling my house and totally changed the layout... thus all the water, hydronic and DWV pipes had to go. It wasn't worth trying modify the existing system (house built in 50s). The whole system was copper, even had 3" vent stacks. I cut it all out and scrapped the copper, got about $1000 for it. Granted there is still a little bit of copper left (near water meter and around boiler).

I decided to redo the system in PEX. The advantage to PEX is when you install it "home-run" style, ideally you only need 2 connections. PEX is pretty flexible and thus reduces the number of connections needed. I crimped my connections (copper rings). I spent more time planning the system, then actually installing it.

I plan on installing baseboard or panel heaters throughout the house and will use 3/4" oxygen barrier PEX for each loop/room.

You *can* replicate the copper layout, however remember that PEX has a smaller ID than copper of the same "size". As such, the same system in PEX (identical layout and pipe size) will have higher flow losses, which will either need a larger circulator (to overcome those losses) or have reduced heat output (BTU/hr).