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Temporarily Removing Hot Water Radiators

pjorg Member Posts: 3
Hello All,

I am looking for some advice around how to best remove a couple of cast iron radiators in my dining room in order to refurbish the walls behind them.

They are attached to a gas-fired hot water heating system. There are, as I understand it, two zones: one zone goes off and feeds the various cast-iron radiators throughout the house, and one zone that loops through a hot water tank that is our source of domestic hot water. So, even in the warm season, the system is running to some extent to provide domestic hot water.

My wife and I have long-term plans to refurbish each room one at a time, and each room has at least one radiator that will need to be pulled from the wall to allow access. We also will likely have the rads sandblasted and powdercoated while they are disconnected—so it's not going to be a quick disconnect/reconnect.

That said, as far as I can tell most of the rads have only a single shutoff valve, and some of them have none at all. So I'm not precisely clear on what will need to be done to remove these, even temporarily.

It seems like, to the extent that the supply and return lines to the rads in question can be isolated from the rest of the system, that should be done, but then after that, I'm just going to have to drain there rest of the rads on that segment, as well. Is that right?

To the extent that it's true that I'll have to leave significant portions of the system drained for the duration of the work (probably weeks, best case), how concerned about the inside of the dry sections corroding should I be? What, if any, steps should I be taking to mitigate that?

Finally, when refilling, should I be using specially treated water (perhaps distilled) or is water straight from the tap acceptable?


  • Jamie Hall
    Jamie Hall Member Posts: 23,635
    What you can do, and how you can do it, depends almost entirely on how the system is piped. There are three fundamental ways to pipe (and, fortunately, if there are valves on the radiators, even one, you at least don't have the hardest to do!).

    The hardest to handle for what you want to do is one where the radiators are piped in series -- that is the water goes into one, leaves, goes to the next and so on until it finally gets back to the boiler. There is a way to manage that without knocking out the whole system, but it involves a fair amount of nuisance work. Then there is one in which the radiators are fed through specialized Ts off a main, with a bypass between the Ts. And the easiest to cope with it one where each radiator feeds individually off a main, and returns individually to a return.

    So -- the first thing you need to do is to figure out which of the three you have. If you have either of the latter two, you will make life much easier for yourself (albeit at some additional nuisance in the beginning) by draining the system down and then installing a new valve -- I'd suggest a ball valve --on each of the returns. Then as you proceed from room to room all you will need to do is to close both valves to the affected radiators, remove them, do your work, and reinstall them and bleed them. The rest of the system will just continue to perc. along quite happily, and you will only have to drain and refill the system once.

    As to what to refill with, that depends on your water quality. Unless your water is significantly hard, tap water is fine although you may want to add a corrosion inhibitor. Distilled or deionized water is sometimes suggested, and probably better if you have hard water -- but you will want to add a corrosion inhibitor if you use that, as both distilled and deionized are remarkably corrosive. What you DON"T want to use is softened water.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,166
    Another option might be to install a bypass pipe. I'm thinking you may have cast iron radiators or convectors that are connected with a supply pipe in and a return pipe out of the bottom of each radiator. To keep the system operational during the work on each room, you would need to drain the system and remove the radiators in question. Remove the connecting unions from the radiators (or the pipes coming through the floor or wall) and put a connecting pipe from the supply to the return. fill the system with water and recommission the boiler. Upon completion of the renovation work, you drain the system again to reinstall the radiators, fill the system and recommission the boiler.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?