Cast Iron Radiators: Breaking Up is Hard to Do

Scott Gibson

I'm renovating an old house that has a number of cast iron radiators. The largest is 54 inches long and 36 inches high. I can't move these monsters in their assembled state, but I'm reluctant to break them up because they are pretty, ornate, and probably worth something to the right party. If I can get them apart, I can move them in sections. They're held together with a rod and what appears to be a square nut on the end. What are the proper tools for disassembly?

Cast iron radiators were manufactured in sections and assembled into the bohemoths you have in your house with connecting pieces called nipples. Reducing a radiator into manageable pieces amounts to loosening those connections and prying the cast sections apart.

I've never had the pleasure of disassembling a radiator. But my hunch is it's one of those things that could go quickly and easily, or turn into an old-house nightmare.

I say this because of a recent query I had from a man in Philadelphia who was trying to take apart an old radiator so he could replace a broken section. He had tried just about everything to loosen a nut on one end of the radiator, including a four-foot breaker bar. But nothing budged and he was still trying to figure out how the thing was held together. Plumbers he called in for help were stumped.

So be prepared for a setback or two.

The best explanation I found of how radiators are assembled comes from Dan Holohan, a writer with an unusual interest in steam heating systems. He and his wife maintain a website ( with all kinds of information on the subject, plus a lot of other interesting stuff. Dan also has written a book on the topic.

Dan says there are two types of nipples that join radiator sections. One has right-handed threads on one end and left-handed threads on the other. When the manufacturer turned the nipple, it would draw two radiator sections tightly together.

While ingenius, this design had a serious flaw. After a few years of use, the nipples corroded into an immovable blob of metal that you can't take apart. Further, no one makes replacement nipples of this type. If you were lucky enough to get sections apart, you would never be able to get them back together.

The other type of nipple has no threads. These are tapered connections that form a tight seal as forced is applied with a threaded rod and a nut. Logically enough, they're called push nipples and, because your radiators are held togehter with a rod and nut, that's what you're dealing with.

Theoretically, you should be able to loosen the big nut on the end and then force the sections apart with a pry bar or some wooden wedges. Applying heat or a penetrating thread lubricant would probably help, and you might indeed need a breaker bar to loosen the nut.

I admire your interest in saving these relics. For an estimate of their value, try sending a few photos to companies that specialize in restoring and reselling old radiators. That might provide an incentive for wrestling them apart, or good reason to get them out of the house any way you can.


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