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Connections on tankless coil

zepfan Member Posts: 398
I was looking for recommendations on the preferred fittings to use on a tankless coil that is installed in a weil mclain oil fired boiler. The home that has the coil, and boiler is on a well so I don't know if the well water is contributing to the corrosion that is building up on the outer surface of the coil. From what I can tell the FPT connections on the coil have a copper lining, or they are entirely copper. Currently there are stainless nipples directly installed on the heater's outlet, and then switches over to copper piping. I didn't know if it was better to use brass fitting in a different type of sealer, such as leak lock or expando. It seems the stainless steel is having a hard time sealing, or the FPT fittings on the heater's outlet have an issue with the threads. Any suggestions would be much appreciated. Thanks to all


  • MikeAmann
    MikeAmann Member Posts: 998
    edited February 2023
    Dielectric nipples will interrupt the electrical path and help prevent corrosion.
    The stainless fittings have very rough threads when new.
    No matter the type, I always clean the newly cut threads with a wire wheel.
    Use teflon tape AND thread sealant. I like Rectorseal #5.
  • kcopp
    kcopp Member Posts: 4,448
    I think brass will have less issues than stainless. Also some of the imported nipples tolerances are a bit off and will develop issues over time.
    An ideal set up IMO would be male x sweat unions.