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Hot Water Radiator (Cast Iron) Disassembly


I'm taking apart a 100 year old cast iron radiator from a hot water gravity feed system. The radiator is an American Radiator Company brand.

I need to take it apart in order to remove a cracked segment. This is an under window (low) and 14 segment wide unit (42" W x 20" H x 13" D) which is approximately 500 lbs and very rare model. This is my motivation for repair over replacement.

I was able to get the end caps off and see inside. The sections are connected together with straight nipples which have two little nubs on the inside.

On Ask This Old House I saw Rich Trethewey replace a hand valve with a thermostatically controlled unit. He took the valve fitting off of the hot water radiator using a special tool. It was long, step-tapered, round on the tapers, square on the wider end, and had grooves that fit the nubs inside the fitting. He inserted it inside the fitting and then used a pipe wrench to turn this tool. It was step-tapered in order to be used on many different ID size fittings.

When I search the videos on this site, that particular ATOH job seems to be missing. :confused:

I have three questions:

1. What is this tool called?

2. Where can I purchase one?

3. If I have to break out one or two of these straight nipples, is there anyplace where I can find new ones?

Thank-you very much for any help!


I originally remembered Rich calling it a spud wrench. Despite the term "spud wrench" apparently having a more popular meaning for a tool that looks like a pipe wrench, I found out that this is called a "Radiator Spud Wrench". Now any advice regarding where to find the special nipples would still be appreciated.


Re: Hot Water Radiator (Cast Iron) Disassembly

Here is what I ended up doing...

I used a reciprocating saw, an angle grinder, and a sledge hammer to remove the cracked section. This revealed the nipples that hold each section to the next. They are standard nipples about 1 inch long, right-hand threaded on one end and left-hand threaded on the other. The lower nipples are 2" NPT and the uppers are 1-1/2" NPT.

I had to make special long spud key tools for each from scratch.

Reassembly was a simple matter of making new gaskets and cleaning up all the threads. With both halves on the floor, start the nipple in each hole and then carefully line up the adjoining section. Insert the long spud key into the radiator and engage the nipples. Turning one direction pulls the two half together since the nipples have opposite threads on opposite ends.

See this instruction sheet for more info...


Those are new radiators from the UK but the design and assembly is exactly the same as these 100 year old American Radiator Company units.

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