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Ancient Radiant System

Am buying an older house in NY state with a 40+ year old radiant system in slab. Cast iron pipes. Boiler was replaced about 8-10 years ago.

System wasn't working for the inspection. Only one of 3 zones would heat the floor and rooms. It's all on one thermostat, but there are 3 labeled valves coming off the boiler.

Owner has made repairs and says everything is A-OK. He says his contractor replaced the outbound circulator pump and the "auto feeder" on the system. My question is does this sound like the right remedy for the problem?

A friend said that the system may have a leak in the slab pipes. Does this repair fix that, cover it up, or maybe my friend is wrong?

I'm probably going to bring in my own pro-contractor to look at the repair, but wanted to get some advice on what to look for, or a heads up from you guys if their trying to pull a fast one on me. I don't want to overlook what could be a major issue.



  • Tom K
    Tom K Member Posts: 26

    What worries me is that the auto feeder went bad. They are pretty simple in design. Usually the get plugged up with debris from adding fresh water to the system. The next time you go visit the house, there is a screen in the bottom of feeder. Pull it out and see if there is dirt on it. If it was just replaced it should be pretty clean. If not you probably have some leaks. Hope this helps.
  • John Felciano
    John Felciano Member Posts: 411

    I would check for leaks on the radiant side of the system.A few of these systems survived from the golden era of radiant,but many were abandoned due to leaks.

    I've been involved in saving a few of them.We've had good results installing water meters on the incoming water to monitor the system.

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  • Dale
    Dale Member Posts: 1,317
    Good deal

    The house is probably priced right for a very good reason, I would get a price to cut and break up the floor, insulate, lay pex and repour and recover before I bought this place. If it turns out the old pipe is holding pressure you win, if it isn't at least you know costs in advance.
  • bluemoon
    bluemoon Member Posts: 38

    I've run into radiant iron pipe systems in New York City..I was told they used an additive to keep the piping from rotting
  • Dave Yates (PAH)
    Dave Yates (PAH) Member Posts: 2,162
    old radiant

    We care for quite a few of the "antique" black iron burried in concrete circa 1940's radiant systems. They survived longer than the copper in concrete systems due to less thermal stress. The BI and concrete share similar expansion properties.

    One of those homes has 100% radiant ceilings. The new owner couldn't find the heat(G). Concealed panels revealed balance valves and 1/4" copper tubing attached to each black iron loop (somewhere above the ceiling) with bleed valves attached. The circulators are Taco and as old as is the system - shaped like bullets.

    You can have your contractor isolate the expansion tank and observe pressure - providing there's no air in the remainder of the system - a leak will be readily apparent. System should be at room temperature or the water cooling will cause the gauge to drop from contracting in volume. Id it looks like there's a leak, each zone should have valves to isolate which one is a problem.

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