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1920's Cast Iron system

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peterb01
peterb01 Member Posts: 15
edited September 2019 in THE MAIN WALL
Hi All,

I've been inspecting our 1920's cast iron radiator hot water system which uses 1 1/4 and 1" galvanized piping. The system was refurbished around 5 years ago, with new vents and a new on-demand boiler but the original piping is almost entirely untouched.

Several of the radiator valves are leaking or broken and I started a discussion on potential replacement of those here:

https://forum.heatinghelp.com/discussion/170978/radiatior-valve-replacement-1920s-cast-iron#latest

While inspecting the system over the weekend I found several other areas with occasional drips from corroded joints and this has me concerned about the piping that I can't see. If I close the makeup water valve for the system then the boiler will shut down with a low pressure warning within a few days (going from ~12psi to under 7).

The house is 1920's with decorative plater/lath ceilings on the main level (which I don't want to touch) and a finished but very old basement which is going to get renovated at some point. Total sq ft on the main floors is ~2000, with around 11 radiators in all.

We love the radiators and heat and I'm wondering how other folks have dealt with this scenario. At one extreme I can continue to repair leaks as and when I find them - at the other extreme I've seen all of the piping replaced with a manifold and PEX piping.

PS. My local Ontario plumbing/heating firm quoted $ CDN for replacement of the valves and $ to replace a small section of corroded pipe (which I ended up doing myself - and yes, 400l took a long time to drain and refill!).

Thanks,
Peter

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,283
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    Galvanized pipe does, unfortunately, have a way of developing leaks over time. It also has a way of building up a lot of rust on the inside, which restricts flow.

    Therefore...

    I have used PEX to replace both hot and cold galvanized water lines in some properties I care for. For heating, you would need to use PEX-AL-PEX, to prevent oxygen getting into the water. For heating, you would need to check the maximum temperature the pipe you choose is rated for. I have found that it can usually be routed through the existing chases or what have you that have the galvanized in them -- if the galvanized is removed first, which is much easier to say than to do sometimes.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,520
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    @peterb01

    This is what you should do. On a closed loop hot water system the piping should last almost forever. When the water is heated the oxygen is driven out of the water and vented...no oxygen...no corrosion. So the first question is how does the piping that was removed look? It should look as good as brand new pipe on the inside.

    Now, if the system has been allowed to leak over the years ....then all bets are off.

    That being said a 90 year old system will develop a leak here and there from expansion and contraction which can cause a threaded joint to weep and turn into a leak and some valve packing leaks are normal from time to time.

    but the condition of the pipe tells the story.
  • Ironman
    Ironman Member Posts: 7,376
    edited September 2019
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    I'd fix the valves/pipes that are leaking and see if it then holds pressure. If so, and if as Ed recommends about examining the interior of the piping that's removed, then I wouldn't worry about it.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • woobagooba
    woobagooba Member Posts: 186
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    I’m in a similar situation. Reno about to start on multi-level 3k sq ft (total) w full basement. Basement ceiling piping likely to be impacted. I’m tempted to re-route basement ceiling piping as PAP. So I end up w/ mixture of PAP in basement and old piping running up to 1st and second floors.

    Question, will mixture of PAP and old pipe accelerate corrosion of existing pipe? Or is PAP oxygen barrier adequate?
  • Ironman
    Ironman Member Posts: 7,376
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    woobagooba said:

    I’m in a similar situation. Reno about to start on multi-level 3k sq ft (total) w full basement. Basement ceiling piping likely to be impacted. I’m tempted to re-route basement ceiling piping as PAP. So I end up w/ mixture of PAP in basement and old piping running up to 1st and second floors.

    Question, will mixture of PAP and old pipe accelerate corrosion of existing pipe? Or is PAP oxygen barrier adequate?

    You don't wanna do that unless you pump the old and new separately. Water takes the path of least resistance. Given the option of going through a 1 1/2" pipe or a 1/2", which way do you think it will take?

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • woobagooba
    woobagooba Member Posts: 186
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    Ironman said:

    woobagooba said:

    I’m in a similar situation. Reno about to start on multi-level 3k sq ft (total) w full basement. Basement ceiling piping likely to be impacted. I’m tempted to re-route basement ceiling piping as PAP. So I end up w/ mixture of PAP in basement and old piping running up to 1st and second floors.

    Question, will mixture of PAP and old pipe accelerate corrosion of existing pipe? Or is PAP oxygen barrier adequate?

    You don't wanna do that unless you pump the old and new separately. Water takes the path of least resistance. Given the option of going through a 1 1/2" pipe or a 1/2", which way do you think it will take?

    Apologies I should have been more clear. Assuming no issues with matching pipe size. The reno will be disruptive enough in the basement such that we are considering re-piping the ENTIRE basement ceiling supply/return system to the point of connection with the old pipe running to the emitters on 1 and 2 (to remain untouched). Is PAP oxygen barrier good enough such that we won't have an issue with oxygen induced corrosion of the older pipe?

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