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Will there be scaling in 53 year old hot water radiator?

I am planning to purchase a house built in 1949 with hot water heat. The pipes are iron or steel - not copper. The pipes and radiators are original (53 years old) but the furnace itself is only 10 years old.

What is the likely hood that 53 year old pipes and radiators will have problems with lime/mineral deposits and scaling? The radiators feel hot, so does that mean there is no scaling? Is there a good way to check for lime buildup? If lime buildup was a problem, is there any chemical you can add that will remove the mineral deposits without also eating up the pipe?

Also, I have a book written by a home inspector who says that galvanized steel pipes can rust from the inside. What is the likelihood that rust will be a problem?

I was told that even if non-distilled water was used with antifreeze, there shouldn't be any problem, since antifreeze has additives that inhibit rust and mineral deposition. Is that true?


  • Mark Eatherton1
    Mark Eatherton1 Member Posts: 2,542
    As with any hydronic question, the one correct answer is...

    "It depends..."
    In my 30 years of mucking around systems, I have seen some fairly good accumulations of rust in the lower portions of the lowest radiators of gravity systems, but the rust is evidently conductive and doesn't impede the transfer of heat to the point that it is noticeable.

    The amount of rust is dependent upon how much oxygen the system has seen. Oxygen content of the system depends on wether it is a closed loop system or open loop (expansion tank), and how much fresh water induction it has seen.

    Lime scale generally accumulates where the heat is being introduced, not where its being extracted. I seriously doubt that you have a lime scale condition on the inside of the radiators. The boiler, possibly, but the radiators, no.

    There are other water conditioning products that can be used short of using antifreeze. Antifreeze is a major ongoing maintenance headache, that in most cases is not necessary. If you maintain a high pH (above 8) the chances of oxidation causing major problems in your system are held to a minimum.

    As for the galvanized nipple, they generally do get rusty on the inside, but only when there's plenty of oxygen available. In a good closed loop heating system, high quantities of oxygen are not usually present.

    If you can feel good heat coming from your radiators, I seriously doubt that you have a scale accumulation problem. Don't lose any sleep over it. The Dead Men used to say about heating system water, "The blacker, the BETTER" They referred to it as Black Gold.


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