2 Responses to “3 Solar Hot Water Tanks Under Construction”


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  1. Chuck

    Dr. Ben,
    Have you seen any of those “COLLAPSIBLE” solar hot water tanks out on the market? What are your thoughts on using these?

    • Dr. Ben


      Those tanks are basically an EPDM plastic pool liner with mechanical support structures to hold them up.

      1. I don’t recommend plastic for any solar tank. It will not take high temps and pressure. Pool liners are rated ~ 180F max, but plastics operated close to their limit with water pressure applied can extrude at the seams and fail rapidly. They might work well with low efficiency systems that don’t get that hot, but they are not good solutions for serious professional systems. They are mainly for do-it-your-selfers. Have you ever seen a plastic water heater?

      2. DIY assembly. Components may consist of a wood frame with insulation wrapped around the outside. Metal sheets are wrapped around the insulation and held on with big bands. The pool liner is installed inside the frame structure. These are definitely not a factory made, quality controlled product.

      The “tank” sits on the floor, so keeping floor area dry is mandatory, or the wood will rot and the heat will be dumped in the floor. These tanks are meant for small systems up to ~ 300 gallons.

      3. You cannot install a commercial heat exchanger in one. Boiler tube and finned coil type exchangers cannot be used with plastic tanks because they cannot be mounted horizontally through the tank face. One company talks about 3/4 in copper coils with capacities of 26,000 Btu/hr and 39,000 Btu/hr capacity. We regularly use 75,000 – 250,000 Btu/hr sizes.

      4. Integration: Pumps, etc. must be site installed and piped and are generally not specified or supplied with the tank. They cannot be factory installed and wired because there is no tank structure to mount on until the pool is constructed.

      I have nothing against DIY systems, but these plastic tanks are not for professional use, and I would never use plastic for any part of a solar system (excluding pool systems which don’t get hot).

      I hope that helps!
      Dr. Ben

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