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Reactivating an old radiant heating system

aschwa Member Posts: 24
Hi all-

I moved into a home in the San Francisco Bay Area last year. It was built in 1964 and renovated in the late 90s.

The home is a two-story home.

I recently discovered that the previous owners who did the remodel in the late 90s disconnected the original hydronic radiant floor heating system because they were concerned about leaks (they apparently had a leak and decided that they wanted to disconnect the whole system instead of dealing with it). They put in a forced air system in its place.

Underneath the carpet on the second floor, I've discovered the pipes for one of the two floors coming up where the previous remodel cut them off. I suspect that it won't be too hard to find the pipes for the first floor.

The pipes themselves are copper (not galvanized steel fortunately). I think that they are embedded in concrete (I don't think gypcrete was used in the 60s).

Here's my question: is it worth trying to reactivate this 50-year-old radiant floor heating system that was drained 16 years ago? Or is it likely to be more trouble than it's worth? We're about to start a remodeling project of our own, so now would be a good time to do it. Will copper pipes degrade because they were dry for 15 years? Are copper pipes that were embedded in a concrete slab 50 years ago likely to have much life left in them? Is this a bad idea for any other reason?

I suspect that some of the pipes may have been cut during the previous remodel to open up a foyer area, but I suspect that that will only affect a small portion of the system and can presumably be identified by a leak detection.



  • SWEI
    SWEI Member Posts: 7,356
    Pressure test the pipes with air (no more than 15 PSI to start.) See how long that holds.
  • aschwa
    aschwa Member Posts: 24
    SWEI said:

    Pressure test the pipes with air (no more than 15 PSI to start.) See how long that holds.

    The pipes have been cut off. Is there a DIY way to pressure test cut off pipes, or do I need to call in someone like American Leak Detection?
  • SWEI
    SWEI Member Posts: 7,356
    Any competent plumber can handle it -- no need for fancy leak detection until you know at least what parts have leaks.

    SharkBite fittings work well for this. You'll need one plug and one male adapter to test a loop, along with an air test gauge. If the pipes are 3/4" copper, you could start with one each of these:


    You'll also need a bit of Teflon tape or pipe dope and an air compressor (or a decent bicycle pump.)
  • aschwa
    aschwa Member Posts: 24
    If the pipes can hold pressure, would you recommend that I reactivate the system despite its age?
  • Rich_49
    Rich_49 Member Posts: 2,721
    I don't know swei . They may hold pressure now but in a few years ? Lotsa lime in that there old cementitious detail . Ever see those copper pipes after 1/2 a century in concrete / cement ? It can be quite ugly .
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • Paul48
    Paul48 Member Posts: 4,469
    My two cents..........I wouldn't do it. There was and is, no way to deal with it if it has begun to fail. It's like only replacing a rotted out muffler on your car. It will just leak elsewhere. I don't care for the previous owners choice of heating systems, but agree that it should have been abandoned.
  • Paul Pollets
    Paul Pollets Member Posts: 3,617
    Levitt systems have a 50 year life expectancy. Not worth the investment to fix the old. The Bay area has a housing market that should accept a hydronic renovation without loss of property value.
  • SWEI
    SWEI Member Posts: 7,356
    Generally agreed, but most of us have come across at least one of those old systems that still held pressure. My take is that it's worth testing.

    For the record, I would never connect one to an autofeeder. Something akin to ME's PIG (or just an oversized expansion tank) would be in order. This requires a competent hydronic pro -- check references well!
  • RobG
    RobG Member Posts: 1,850
    Isn't Allen Forbes in SF?
  • SWEI
    SWEI Member Posts: 7,356
    East Bay, I think - pretty sure he's on the road at the moment. Eichler country for sure.
  • aschwa
    aschwa Member Posts: 24
    Is there a way to install a new radiant floor heating system without raising the floors? Would this involve demolishing a few inches of the existing concrete on the first and second floor? Or is this impossible, because it would damage the foundation?
  • SWEI
    SWEI Member Posts: 7,356
    Radiant ceilings and walls work at least as well as radiant floors do. Lacking sub-slab insulation, they will work far better (and likely save 20-30% on fuel depending on wall/attic insulation values.)
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    My house was built in 1950 and the downstairs is radiant slab at grade. Heat there is mostly 1/2 inch copper tubing. If I turn the makeup water off, it will hold pressure until I get tired of looking at the pressure gauge. Several days. So I suppose it is not leaking.

    Maybe they used heavy wall copper tubing. Maybe the concrete mix contained less harmful stuff (fly ash?). Anyhow, it still works. The house across the street still works too. We have both replaced the boilers. Mine is now a gas fired mod-con. I think the guy across the street still uses oil.
  • hot_rod
    hot_rod Member Posts: 19,273
    What I have found with tube in concrete is that it will last IF it is encased completely and remains dry.

    If the tube touches moist fill below, or the slab has moisture, then corrosion is possible.

    Tough to know that, so it becomes a roll of the dice, with metallic tube in, or partial in concrete slabs.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • 4Johnpipe
    4Johnpipe Member Posts: 479
    Copper in concrete I would say professionally no. They obviously had a leak and decommissioned the system for a reason. I have seen what used to be tubing as just holes or channels in the cement. No copper visible. Once a leak starts Lyme gets introduced into the system. This could happen for months even years before the leak shows itself. Meanwhile the owner can't understand why they suddenly need so many parts changed near the boiler. Finally it's a leak and it's done.
    Research other means of hydronic heat but do not put a penny into the system you discovered.
    Considerate People, Considerate Service, Consider It Done!
    email: [email protected]