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Thread: Iron radiator piping life span

  1. #1
    DIY Junior Member milesdf's Avatar
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    Default Iron radiator piping life span

    I asked this question in the plumbing forum (as part of a larger question), but I think it might be more appropriate here.

    I am embarking on a full kitchen renovation soon, and will be exposing the piping for at least 2-3 of the 4 upstairs radiators in the house, which is almost 80 years old (1936). The system is currently a hot water system, and it may have always been hot water (2 pipes), perhaps a gravity system (pipes slope down to boiler), perhaps always sealed (no signs of piping in attic). The radiator pipes appear to be original, and iron, with a giant unknown being that the house sat foreclosed for several years, which resulted in the boiler being rusted through, and two downstairs radiators completely bursting from freezing (I replaced them and had the system pressure tested).

    I haven't been able to find any information on how long iron hot water radiator piping is expected to last.

    Can I expect much more life out of the 80 year old hot water radiator supply and return lines? Or should I outright plan on replacing them? What's the expected lifespan on these? Should I worry about replacing these if they show no sign of leakage or corrosion? It is also possible I could replace just one short downstairs feed and inspect the inside of the piping, would the inside of one pipe be indicative of the inside of them all? Would I have to inspect the inside of an elbow?

    I was looking into replacing these with ox barrier pex, but it really feels like a crapshoot as to what would last longer, brand new pex or old iron. Perhaps new black steel or copper? I am capable of replacing this piping, so really the only investment would be materials and time, but perhaps the best move would be to leave it be?

  2. #2
    In the trades Dana's Avatar
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    As long as you don't introduce air into the system on a regular basis iron pipes can last a very long time, but given they are over 75 years old, replacing the stuff you can't easily get to post-rehab is a good idea. (And if it's routed between the studs of an exterior wall, you may want to figure out how to move the pipes fully inside the thermal envelope of the house, even if it means boxing-in a small plumbing chase.)

    Gravity/convection hot water systems all had HUGE pipes, 4"+ for both supply and return. If smaller than that it's more likely to have originally been 2-pipe steam, later reconfigured for pumped hot water.

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    DIY Junior Member milesdf's Avatar
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    Quote Originally Posted by Dana View Post
    As long as you don't introduce air into the system on a regular basis iron pipes can last a very long time, but given they are over 75 years old, replacing the stuff you can't easily get to post-rehab is a good idea. (And if it's routed between the studs of an exterior wall, you may want to figure out how to move the pipes fully inside the thermal envelope of the house, even if it means boxing-in a small plumbing chase.)

    Gravity/convection hot water systems all had HUGE pipes, 4"+ for both supply and return. If smaller than that it's more likely to have originally been 2-pipe steam, later reconfigured for pumped hot water.
    Thanks for the input. There are 3" pipes in the basement, I think that would be another benefit of re-piping, moving away from those (eventually).

    Any preferences on material to replace with? Ox barrier pex appeals the most from an ease of installation perspective, I'm unsure of the longevity of it though. Has anyone ever seen any failures with it plumbed to radiators, 180 degree max temp? Most seem to be warranted for only 10 years? (I understand as DIY, warranties may not apply)

    Pex-al-pex seems like it might be a better material, but the lack of standardization and fittings scares me for fixing down the road. Viega's fostapex seems to be the best quality and perhaps the most supported in the future, but I don't think a 500$ tool investment (1/2 and 3/4 press) is in the cards.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Wirsbo/Uphonor has been in the pex business the longest of any of the remaining pex suppliers. You may be able to buy an expander tool online, and sell it for very small loss, especially if you get a used one, but even with a new one, your overall cost may be small.

    Other than the ox barrier, pex is made in one of three methods, listed as -A, -B, and -C. With type -A as the most flexible (smallest turn radius) and is the only one that can recover from a kink, should you get one, while pulling the stuff during install. The other two require you to cut out the kink and insert a fitting to maintain integrity, so that may be a consideration. Personally, I prefer the natural recovery of the tubing to make the seal verses a crimp that may or may not be either placed properly or crimped properly (both too tight or too loose is an issue). Neither of those issues are there with Uphonor's expansion method, although you still must position the reinforcement collar properly and insert the fitting all the way in for it to make a proper joint. A crimped fitting may end up easier to remove, though - an expanded one generally must be cut off. If you are not careful, though, you can damage the tubing when trying to remove a crimp ring, so you end up with the same issue - cutting it back. Hopefully, you have enough slack.
    Jim DeBruycker
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    In the Trades Tom Sawyer's Avatar
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    Quote Originally Posted by milesdf View Post
    Thanks for the input. There are 3" pipes in the basement, I think that would be another benefit of re-piping, moving away from those (eventually).

    Any preferences on material to replace with? Ox barrier pex appeals the most from an ease of installation perspective, I'm unsure of the longevity of it though. Has anyone ever seen any failures with it plumbed to radiators, 180 degree max temp? Most seem to be warranted for only 10 years? (I understand as DIY, warranties may not apply)

    Pex-al-pex seems like it might be a better material, but the lack of standardization and fittings scares me for fixing down the road. Viega's fostapex seems to be the best quality and perhaps the most supported in the future, but I don't think a 500$ tool investment (1/2 and 3/4 press) is in the cards.
    I have a customer that still has the original gravity hot water system. The boiler, valves, piping and controls were installed in the early 1920's. Only the burner (originally coal fired) was upgraded to power gas sometime in the 40's. Although grossly inefficient and marginally dangerous ( very few safeties and line voltage thermostat ) everything works just fine thank you and he has no plans or desires to change anything. Believe me, I have tried. Lol
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  6. #6
    DIY Junior Member milesdf's Avatar
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    Quote Originally Posted by jadnashua View Post
    Wirsbo/Uphonor has been in the pex business the longest of any of the remaining pex suppliers. You may be able to buy an expander tool online, and sell it for very small loss, especially if you get a used one, but even with a new one, your overall cost may be small.

    Other than the ox barrier, pex is made in one of three methods, listed as -A, -B, and -C. With type -A as the most flexible (smallest turn radius) and is the only one that can recover from a kink, should you get one, while pulling the stuff during install. The other two require you to cut out the kink and insert a fitting to maintain integrity, so that may be a consideration. Personally, I prefer the natural recovery of the tubing to make the seal verses a crimp that may or may not be either placed properly or crimped properly (both too tight or too loose is an issue). Neither of those issues are there with Uphonor's expansion method, although you still must position the reinforcement collar properly and insert the fitting all the way in for it to make a proper joint. A crimped fitting may end up easier to remove, though - an expanded one generally must be cut off. If you are not careful, though, you can damage the tubing when trying to remove a crimp ring, so you end up with the same issue - cutting it back. Hopefully, you have enough slack.
    I'm not terribly concerned with the termination method for the ox barrier pex, I was leaning towards a type A with stainless steel clamps, but regardless, all of the connections should end up exposed, and with the ox-barrier pex which all seems to be the standard size, which I'm assuming will be serviceable in the future.

    I'm more concerned with pex-al-pex, none of it appears to be standardized, making me think the fittings aren't going to be available in the future.

    No support for replacing with black iron or copper?

    Leaving the old is obviously an attractive option. I do have to replace the radiator valves at least, so I should be able to inspect the inside of a little bit of the piping. Is there any sort of test that can be performed on the pipe to determine if it's corroding from the inside? Maybe hitting it with a hammer?

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    DIY Senior Member houptee's Avatar
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    I replaced all my iron hot water heat pipes a few years ago in my crawlspace. The outside of the pipes were badly rusted but when sawzalled out, the inside was like brand new, super clean. I was amazed since they were probably as old as yours. I estimate late 1930's or 40's. I replaced them with 1/2" Oxy Pex with copper crimp rings but I home runned each rad to a supply and return manifold with valves to enable me to isolate each circuit in case of a leak and supply same temperature water to each rad.

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    DIY Junior Member milesdf's Avatar
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    Quote Originally Posted by houptee View Post
    I replaced all my iron hot water heat pipes a few years ago in my crawlspace. The outside of the pipes were badly rusted but when sawzalled out, the inside was like brand new, super clean. I was amazed since they were probably as old as yours. I estimate late 1930's or 40's. I replaced them with 1/2" Oxy Pex with copper crimp rings but I home runned each rad to a supply and return manifold with valves to enable me to isolate each circuit in case of a leak and supply same temperature water to each rad.
    How big are your rads/rooms? My bathroom is small and the radiator is small, so I'm assuming the 1/2" oxy pex would work well for that, there are two small bedrooms, roughly 10x11 each, with larger radiators, I'm not sure if 1/2" will work or if I should use 3/4". Have you had any issues with noise, leaks, or expansion/contraction with the oxy pex? The manifold also sounds very attractive.

  9. #9
    DIY Senior Member houptee's Avatar
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    The rads are all various sizes and rooms about the same size as yours. The old iron pipe system was a 1" main loop with 1/2" tees to each rad. the 1/2" branches even went up to 2nd floor rads also. I had no problems at all after the entire system was changed to all 1/2" oxy pex but like i said i home runned every rad with its own supply and return pipe. It does make a little expansion noise as it heats up but i went back and put foam pipe insulation on those noisy areas since the noise was where tubing rubbed on wood joists. Also make holes large enough to allow room for expansion of pex.

  10. #10
    In the trades Dana's Avatar
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    With only 3" piping I'm thinking the original system was most likely 2-pipe steam, not a thermosiphon/gravity system, but it doesn't really matter. If it's in an exterior wall, rip it out and bring the new pipes indoors where they belong.

    Wirsbo has an ongoing experiment running PEX at ~200F (20F above the operational service rating of the stuff) and it's been working fine for about 3 decades now.

    But if you're concerned, most people can handle sweat-copper plumbing competently with a minimum of practice.

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