Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit

Saltwater Pool heat exchanger fittings

SpeyFitter Member Posts: 422
edited April 2020 in THE MAIN WALL
Hello Ladies & Gentlemen,

Been a while - got a titanium pool heat exchanger Ill be likely installing in the somewhat near future on a wall mount boiler to heat a saltwater pool. Its an all metal fully welded titanium exchanger. I know the exchanger is the critical part in the grand scheme, however my concern is the fittings on the saltwater pool side that connect it to the plastic. For those not aware my experience is based on conversations with technical people at IPEX and some experience as a result of those conversations in that connecting metal to PVC/plastic via a threaded connection is always best done with a male metal pipe MIP nipple/thread and a female pre-stressed plastic FIP adapter (with the metal ring). This is over screwing a plastic MIP into a metal FIP which can suffer overtime due to the differing expansion rates of the metal vs plastic overtime (never mind screwing a metal MIP into a plastic FIP without any metal reinforcement ring or pre stressing of the plastic). This is also beneficial for sensor wells on pool piping where you have a male/MIP well thread and when you use the pre-stressed plastic FIP's with the metal ring it reduces the likelihood overtime of leaks/issues/cracks. My principal concern is since the Titanium pool HE has female fittings on the pool side, while I know stainless pipe nipples will likely hold up a good while against the saltwater (and I know the importance of introducing saltwater downstream of the HE where possible), I was wondering if anyone had any luck sourcing either Titanium or Cupronickel Pipe nipples which I am told and from research will stand up better to salt water than stainless. I recognize they may be more expensive, especially in 1 1/2" size but it's only two nipples so.......or should I just use stainless nipples?
Class 'A' Gas Fitter - Certified Hydronic Systems Designer - Journeyman Plumber


    EBEBRATT-Ed Member Posts: 10,328
    I have no experience on salt water. The best way to connect plastic to metal is with flanges but you method also works
  • pecmsg
    pecmsg Member Posts: 2,340
    Plastic to anything........pipe dope, NO Teflon.

    I also prefer Flanges.
  • hot_rod
    hot_rod Member Posts: 15,040
    Maybe source some 316TI nipples the titanium alloy looks like the best SS grade. Then Fernco from that nipple to Sch 80 to plastic to avoid any other threaded connections.

    If you have access to PP fusing equipment, maybe that is the best plastic option? AquaTherm or others.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • PerryHolzman
    PerryHolzman Member Posts: 234
    The issue you need to be aware of is galvanic corrosion of the fittings that screw onto the Titanium.

    None of the 300 or 400 series SS are recommended for direct contact with the Titanium because they have both an "Active" and "Passive" phase, which are far enough apart that under the right situation these metals can galvanically corrode within themselves (different metal grains become Active and other grains become Passive - not real common; but, I've seen it and its in the literature).

    You cannot normally control if say a 304 or a 316 SS will be in its active or passive stage, and the metal grains can switch while in service if certain things are spilled on them.

    Here is a good galvanic reference chart:

    I once spent in the range of $20,000+ while working at a nuclear power plant to perform specific galvanic testing of various materials to figure out how to build heat exchanges without galvanic problems with highly Nobal materials that were close to titanium on the galvanic charts after our plant had a series of HXs with massive galvanic corrosion issues after being retubed with "SeaCure" tubing.

    2205 Duplex SS was the intermediate material that worked; and that is what you should be looking for. It also appears that Alloy 20 SS is also available and suitable as well.

    Both materials are regularly available in plates, pipes, pipe fittings and flanges, and tubes. I am sure there are tube fittings that match (although they might be a slightly different alloy as they would need to be harder than the tube).

    If you are having difficulty finding tube fittings for your application. Put a 2205 Duplex SS or Ally 20 SS pipe fitting (coupling, bushing, nipple, etc.) between the Titanium and a 316 SS fitting.

    I wish you well with this,