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Flexible connections for cast iron hydronic baseboard install

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JimP
JimP Member Posts: 87
in Radiant Heating
Hello. I’m considering the use of flexible stainless steel connectors for a hydronic cast iron baseboard installation. I’m concerned about the rubber seals and how they will hold up over time with the very hot water. Does anyone have experience with these connectors in a hydronic system. Should I be concerned that the rubber seals may start leaking? Here’s the product that I thought I might use:

https://www.siouxchief.com/products/supply/specialized-supply/sweat/water-heater-connectors/fip-swivel-straight-flex/stainless-steel

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  • STEAM DOCTOR
    STEAM DOCTOR Member Posts: 1,968
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    What are temp ratings? Would never consider using and certainly not behind a wall or a ceiling. Even on water heaters, they only need to last as long as the water heater. You don't want to replace them every 10-15 years. You need "forever" piping. Not a good idea iny opinion
    Mark @ Radiant Works Inc
  • ScottSecor
    ScottSecor Member Posts: 855
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    We've never used this type of flexible connector for anything besides commercial pumps, but they did hold up well for years. I've seen many of them on commercial jobs and do not recall one that failed. https://www.hosecraftusa.com/accessory/TT?gclid=CjwKCAiAsNKQBhAPEiwAB-I5zQsjpcnWnUq24eKQFFcZNH0_3AOzClejaGoihlyfjZ2giNYdABG3ZRoCxw8QAvD_BwE

  • psb75
    psb75 Member Posts: 833
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    You definitely need to check the mfg. spec sheet for the temperature ratings on this specific item.
    Hydronic heat is often hotter than domestic hot water. Then...there is the potential issue of glycol as well.
  • Ironman
    Ironman Member Posts: 7,376
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    Burnham offers CSST connectors for Baseray that have no rubber seals. You should use those, not ones that are made for water heaters.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    Rich_49
  • hot_rod
    hot_rod Member Posts: 22,143
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    We have been using corrugated stainless tube for solar thermal piping. The evac tube systems can go well over 400F. Some are compression style, some use fiber washer connectors. About the same fitting as you use with CSST gas piping.
    I have used CSST gas piping on a few home hydronic projects, pressure and temperature rating should be fine, plenty of fitting options.

    There are companies that will build special size rubber like they use in hydronic coil kits. Metraflex will build stainless braided connectors.

    Copper water heater flexes should work, maybe get some peroxide cured EPDM gaskets for them. I think McMasters has high temperature gasket, or someone online.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • JimP
    JimP Member Posts: 87
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    Thank you all for the comments and advice. Although these connections will be exposed I’m not going to use them. They’ll be a maintenance problem for sure!

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