Home>Discussions>INSULATION & HVAC>Adventures in Radiator Restoration
4 posts / 0 new
Last post
Adventures in Radiator Restoration


I have a home in central NJ built around 1950, with cast iron hot water radiators. I've gotten myself into a quandry with one of them. Here's the story.

A few years ago I noticed the radiator in an upstairs bedroom only got lukewarm. I had a contractor look at it while he was there to fix the boiler, and he observed that it was WAY to big for the room, and if he made it work right I'd get roasted like a Thanksgiving turkey. Since the room got warm enough as long as I left the hall door open during the day, so I took his advice and left it alone.

Now I'm remodeling the room, and the radiator had to come out, so I wanted one the proper size. At first I thought I would have to replace mine with a restored, used unit of the proper size. But info I found on the web suggested I could shorten and refurbish the one I had. It's a five-column, 33 inch high unit which had 20 sections. Someone did a heat loss calculation for me and determined I only needed 9 of those sections. I unbolted it split it apart using some wedges I cut from 2x4s. It came apart with little drama. I removed the extra 11 sections from the middle, and took to two ends, now with 4 and 5 sections, to a restoration shop.

Here's where things got a bit off track. On the web I found radiator specialist companies (located nowhere near me) that said they could shorten or lenghten their radiators as needed. I managed to find one shop that restores radiators about an hour and a half away, so off I went. Turns out, this particular shop restores lots of radiators but doesn't resize them, and nobody there had ever put one back together. (This was a communication failure on my part.) So now I have two freshly restored radiator halves that need to be re-united. I haven't called my heating guy yet, but I don't know if he's ever delt with a situation like this.

An older gent I met at the shop said I need to put a sealer on the joint. I'm not sure what to use. I still have the surplus sections behind the house. The sections have male and female fittings, and the male portion appears to be cast or welded to the section. I don't see any evidence of sealent. When I fit two sections together they slide in with only about about 1/16 inch left to go. I'm thinking (hoping) tightening the nuts on the threaded rods will pull it the rest of the way together.

So what should I do next? Does a sealer need to be used, and if so, what type? Should I call my heating contractor and ask him to put it together? (I'll need him to rough in the new copper lines too.) Would the average heating guy think this is no sweat, or will he look at me like the Buick parts counter guy when you ask for a taillight for a '72 Opel Manta? Your advice is much appreciated.


Re: Adventures in Radiator Restoration

I believe I read someplace that they are press fit. It sort of makes sense because a sealant wouldn't hold up over time against hot water and steam.

Re: Adventures in Radiator Restoration

Yes, the radiator you describe DOES need to be press fit together (the fact that you were able to separate it with wood wedges verifies this).

There is a press tool that is used for this purpose, but only the older heating contractors may be the only ones that provide this service; check the Yellow Pages under "Heating Contractors" & call a few; also check "Plumbing Supplies-Used", "Salvage Yards", etc.

I would contact the heating contractor you mentioned to see if he/she does it; the job is easily done, but you want some guarantee against a leak once the radiator is back in service.

One way to press the sections together is to remove the nuts on either side of the rad (apply penetrating oil the nite before), & slip a piece of 1 1/2" black pipe (steel pipe) that has been threaded on either side all the way thru the 2 sections.

Large washers & bolts are then attached & slowly tightened until the sections are pressed together.

The same has to be done to the bottom part of the rad; the 2 long, thin thru-bolts & nuts you removed that hold the rad sections together, have to be re-installed, using 2 shortened versions to account for the rad's shortened length.

There is a high heat caulking compound available at plumbing/heating supply stores for $10/tube, but I don't think it's necessary.

It's a good idea to pre-test the rad with 20 psi of air before reconnecting to the heating system.

One bottom side of the rad is sealed with a screw-in plug & the open side is fitted with a schrader valve (regular auto tire air valve); a bike pump is used to pump air in; apply soapy water or bubble-making solution to all the rad seams; if there is no audible leak, or nothing shows on the bubble solution for 20 minutes, the rad is ok; the tiny valve inside the tire valve can be screwed out to let out the air.

It should be noted that you can put any type of hot water convector in the space from which you removed the rad; high output, double ganged baseboard, for example, steel panel radiators, hot water convectors, etc.

Browse the Beacon-Morris site below for ideas; click onto products -> residential -> convectors, etc.

The btu/hr needs of the bedroom can be calculated (assuming 8' ceilings) by assigning 30 btu/hr per sq.ft.; thus a bedroom 15 X 15 = 225 sq.ft. X 30 = 6750 btu/hr to heat this room.

Baseboard supplies 600 btu/ft; high output 800 btu/ft; convectors, steel panel rads & cast iron rads vary.

There is no guarantee whatever convector you put in there will heat up; it could be a blockage (often air) in the supply piping leading to the bedroom, or improperly installed piping (risers).

It's a good idea to open up the other 2nd floor bleed valves & inject some air with the bike pump into the bedroom risers before re-installing the rad (do not use a compressor-compressed air for this); this is often enough to clear any blockage.

Post back; let up know how you make out.


Re: Adventures in Radiator Restoration

Jacktheshack and I both mentioned pressing the sections but forgot to mention "DO NOT USE THE THREADED RODS TO PULL THE SECTIONS TOGETHER" it will put to much pressure on a small area of the cast iron and may cause it to break.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.