Radiator Pipes - Replace Cast Iron w/Copper?

David_18

Hi all:

So my wife's not giving me a second change on the black pipe install (had a few leaks at joints). Per previous post, I had to re-run black pipe (used it because that's what the used before) to the radiator in the bathroom after sistering joists, etc. There is about 12 linear feet of pipe with many unions. Had to use many unions due to installing between existing joists.

So, question is, since my wife has called a plumber, is it better to have them continue with black pipe, or have them switch to copper? If they want to switch to copper, dialectric unions or no? I've read good and bad.

Any advice to help me ensure the job gets done right would be appreciated.

Best Regards,


David

michael_15

I'd say no to copper

I'm not a pro (I'm a chemist by trade) but I'd say no for two reasons, one being the expansion of copper with temperature considerably greater than that of iron (bad given the temperature fluctuations that always happen) and the other being that, well, it's not black pipe, so you have cross-metal corrosion issues without some kind of sacrificial anode or other protection at the joints (which may be what your "dielectric unions" are).

In any case, I figured that if I replied, it would send your question back to the top of the list, where a real pro can probably answer your question!

jim murtaugh

pipes

is this h20 or steam

J Persons

Replacing black iron with copper

Good to hear you are thinking. Hydronic systems traditionally were piped with black iron for cost and availability reasons. If the fluid is self contained and lacks a source of oxygen to help induce corrosion, the piping will not show deterioration even if copper is used. The dielectric unions you suspect are needed are primarily to meet plumbing code requirements on domestic drinking water / water heaters where highly conductive mineralized water enhances the galvanic cell generated between iron and copper piping. (FYI in my area dielectric unions are a bit of a joke and usually become the sacrifical anode and begin to leak at about the same time the waterheater is about to blow.) I cannot recall ever seeing a dielectric on a boiler. Boiler water should be at equilibrium with the metals in the system and therefore not require any form of dielectic isolation. From personal experience I've had great success using the Rigid Pro-Press system for speedy repipe applications. You may not find many wet-heads using this method yet but it certainly is a great time saver and connections on copper are rated for 600 psi. You mentioned running lines through sistered floor joists---Ever consider using PEX tube with crimp connections to make the piping run without the need for unions? This is another technique I use for difficult access applications. We run up to One inch size PEX which handles most any radiator made for residential applications.