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Old cast iron radiator refurbishment and installation

Hi there,

I had a question a very long time ago regarding thermostatic valves and cast iron radiators. on this forum. I am a private individual, so please bear with me.
I moved into another house a few years ago, so I don't have my old radiators anymore... but I am still in France.
Recently, I got my wife's approval to get old ornate cast iron radiators again on the new (to us) house. It seems that now, we have tons of valves to chose from (in fact, maybe 10 or 20 different models, but named differently at each store). I still have a question regarding these. Most of them are labelled 15x21 (½"), but is this tapered?
And regarding these radiators (I now have 3), some of the caps are 20x27 (¾") threaded, some are 15x21 (½"), and standard bushings seem to screw in easily. So I hope that I would be able to install old looking new valves easily.
I will have to remove the end caps (plugs/bushings, how should I call that?) to remove the inside gunk and remove broken elements. I'm still storing tools up to remove caps and unscrew elements.
I haven't been able for the time being to unscrew the caps, as my spark-plug wrench is not big enough, but it looks like the top caps are 1½" and the bottom caps are 2".

The main problem I see is that some of the caps have big holes (bigger than ¾"), so that I should change them, but I can't seem to find replacement plugs. I can find ornate or plain 1" or 1½" end caps, but can't seem to find reproduction 2" end caps. Do you know if/where I could find some?
If it does not exist, are there somewhere adapters that could fit in the big hole, be flush with the end cap so that I can screw in a valve without the assembly getting too big and bulky?

The other problem I have with these radiators is getting rid of the broken elements.
I found a fantastic assembly toolkit (out of stock), but it won't work for the 2" nipple (if that's the case, I don't know yet their size, but the end plug seems to be that size). I know I could get a steel rod with a piece of steel at the end, but I can't weld unfortunately.
So, do you know any supplier of different sizes of assembly heads like this one:

Thanks a lot.


  • Jamie Hall
    Jamie Hall Member Posts: 17,039
    Slow down! Radiators don't have anything inside to break. Nor do they accumulate much gunk - and what little they do accumulate you can wash out.

    What they do do is sometimes they develop leaks between sections. So... if this is a hot water system that they are going on, you do want to check for leaks: -- figure out a way to fill them with water or air, and see if they hold.

    If they leak between sections -- not all that likely, but it happens -- you will need to disassemble them, but they don't have threaded nipples between sections -- they push together and are held by various clever tension rods (the top radiator has single rods, for instance, top and bottom). Trick there is to loosen those rods and take them out, then very carefully pry apart the offending sections.

    Since you are in France, it's a bit hard to say from this side of the pond what the threads are for the spuds (the pipes which screw into the radiator openings) are, nor can I enlarge that one picture enough to see if the pipe I see is what I would think of as a standard spud -- which is actually half of a union, the other half being on the valve.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Gounthar Frankfurt
  • Thanks Jamie. Yes, this is for a hot water system, and there are leaks, not between sections, but in some broken sections.
    The 3 different sellers told me the radiators were leaking, and you can clearly see it (well, if I gave you the right pictures) where bad welds have not been sufficient to contain the water.
    So I have to get rid of some sections.
    I got low prices on those radiators in order to come back into the game with specific tools, so that I can get more of them for other rooms.
    I'm pretty sure these radiators have threaded nipples, which was pretty common in France, but as long as I don't remove the end caps, well, I'm not able to prove it. :)
  • As for the leaks, here are two examples of leaky/welded/broken sections:

    And an example of a leaky seal:

    Top caps:

    Bottom caps:

    Regarding the rods, I guess that's the way it used to be before the threaded nipples, because the white radiator with rods is way older than the blue one (maybe around 1880, and the blue one is around 1905 I guess).
    I had never encountered one... We'll see what I can do.

  • mattmia2
    mattmia2 Member Posts: 3,949
    They probably froze.
    Gounthar Frankfurt
  • I'm trying to install new valves on the third radiator, which is not broken nor leaking.
    I removed one of the bushings: the inside is 3/4, and the outside is almost 1":

    To avoid using too many adapters, I will get a new end cap

    in a few weeks with a 1/2" threaded hole, but for the time being, I will install the radiator with adapters, as it's starting to get cold.
    By the way: we generally say that if you look at the front of the radiator, the right end cap has a Right Hand thread, and the left one is a Left Hand thread. The problem I have is that the paint is as bad on the two sides, so there is no way to tell which side is the front and which side is the back.
    I'm sure some of you can "read" the threads just looking at them, but not me. Do you have any tips to share?

    Regarding the hole in the cap, is the 1" hole tapered or not? I have to find a way to better clean the threads, but for the time being, I can't screw the existing adapter its whole length in.
    What kind of keywords should I use to find the right adapter? 1" to 1/2" coupler adaptor?
    On this side of the pond, it looks like it's easier to find brass adapters instead of cast iron adapters, we'll see if I can find one the right size.
  • Tonight, I screwed a 3/4"-1/2" adapter I had in the end cap holes, and it does not got to the end. I guess the hole is tapered and the adapter is not.
    I know nothing about BSPP and BSPT, but I guess radiator end caps are tapered, as radiator valve coupler adaptors... and maybe not regular plumbing adaptors.
  • retiredguy
    retiredguy Member Posts: 487
    edited September 2019
    Radiators with rods used to hold the radiator together are of push nipple construction. If they do not have rods, then they are probably screw nipple construction. American Radiators, Corto and Peerless are screw nipple construction. The Corto and the Peerless were made by American Radiator. Corto radiators were designed by Louis Courtot, a French engineer, affiliated with American radiator. I did very little work with screw nipple radiators. National and Arco radiators are of push nipple construction. To separate a push nipple radiator I used to take out the rod and nut, and use wooden wedges and a 4# hammer to separate the sections. Radiators can be lenghtened or shortened. If an end section is broken or cracked you need to find another end section of the same size radiator. You can clean the mating pieces with a fine steel wool and not with sandpaper, When reassembling the radiators I used an RTV silicone found at an auto parts store as a lube and a sealer. If you have any 1/2 unions to remove (spuds), they will come out but you need to be careful. I used a "spud wrench" on the inside and a small pipe wrench on the outside with 2 guys turning the same way at the same time. Pipe threads can be chased with a pipe tap. (I had 1/8" through 4" in my service van) 1 last thing, if you can not get the plugs and/or bushings out an experienced pipe guy can cut them out for you. You have a great project ahead of you..... good luck
    ethicalpaulGounthar Frankfurt
  • ethicalpaul
    ethicalpaul Member Posts: 3,122

    Tonight, I screwed a 3/4"-1/2" adapter I had in the end cap holes, and it does not got to the end. I guess the hole is tapered and the adapter is not.
    I know nothing about BSPP and BSPT, but I guess radiator end caps are tapered, as radiator valve coupler adaptors... and maybe not regular plumbing adaptors.

    Can you post a picture of it with the adapter in?
    1 pipe Peerless 63-03L in Cedar Grove, NJ, coal > oil > NG
    Gounthar Frankfurt

  • Gounthar Frankfurt
    Gounthar Frankfurt Member Posts: 25
    The radiator has now been painted (not the final paint, just so we know what it will look like):

    I found an almost correct looking valve:

    whose radiator coupler is unfortunately 1/2 BSPT (and the bush end hole is 3/4 BSPT). I can find the adapter

    online for a fair price but they won't sell to France...
    I'm kind of stuck for the time being. If one of you is living in the
    UK, your help will be really appreciated.
  • ethicalpaul
    ethicalpaul Member Posts: 3,122
    All very fancy! Did you put any pipe dope or teflon tape on that bushing?
    1 pipe Peerless 63-03L in Cedar Grove, NJ, coal > oil > NG
  • Gounthar Frankfurt
    Gounthar Frankfurt Member Posts: 25
    Nevermind, the adapter fits only the valve in the previous picture, and not the one that I bought.
    I will then use a standard radiator brass reducing bush from 3/4 to 1/2 (not tapered), or reuse the old steel reducing bush which may be tapered.
    It looks like the new valve couplers are not tapered either...
    I guess we'll see how all that connects.
  • Gounthar Frankfurt
    Gounthar Frankfurt Member Posts: 25
    edited October 2019

    @ethicalpaul : I don't know yet if I have BSPT or BSP threads, so I will go with tow and grease.
    Wish me luck!
  • JakeCK
    JakeCK Member Posts: 382
    Ooooo pretty.
    Gounthar Frankfurt
  • Gounthar Frankfurt
    Gounthar Frankfurt Member Posts: 25
    I tested the watertightness of the radiator last week-end (better late than never).
    It did not leak. :)
    I use several adapters to connect valves, and unfortunately, one of the adapters is stuck. There is one hexagonal hole, but it got rounded at first try. :'(

    It was bound to happen, as I think the thread of the cast iron end cap is 3/4 BSPT and the thread of the brass adapter is 3/4 BSP.

    So, I now need something to get rid of this adapter (and not a saw, because I'm afraid of damaging the cast iron threads).
    I thought of getting a stud and screw extractor set, but I should maybe get for BSP and not NPT (or it does not matter?).
    Then I thought of getting a straight flute screw extractor, but I don't know if this would work.

    I also thought of brazing a 1/2 plug in it, and try to unscrew both of them.

    Any other idea?

  • mattmia2
    mattmia2 Member Posts: 3,949
    edited October 2019
    You need to find an extractor that has an OD the same as the ID of the stuck adapter, what it is called ,if it is NPT or BPT or and english or metric pitch and size doesn't matter. Be careful because the outward pressure from the taper of the extractor screwing in to the fitting can put enough outward pressure on the CI to crack it.

    You can also cut a little wedge or 2 out with a small hacksaw or thin sawzwall blade to free it.
    Gounthar Frankfurt