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Which indirect water heater is better? Alliance 35SL versus Heat-Flo 40

Hi all,

We are adding an indirect water heater in our two-story home to try to save some oil and have more hot water than what the boiler's coil can produce by itself.

We have two bids with very similar pricing. One contractor recommended to install the Alliance 35SL water heater whereas the second one recommended the Heat-Flo 40. I am listing their respective data sheets: The Alliance one comes with a 10-year full warranty whereas the Heat-Flo comes with a lifetime limited warranty.

Which one would you recommend? Is one objectively better than the other?


  • Fred
    Fred Member Posts: 8,542
    It looks like there is a Lifetime Warranty option available for the Alliance, also.
    bob eck
    EBEBRATT-Ed Member Posts: 15,616
    I have herd that the Heat-Flow is a good unit
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
    I've had excellent results with Heat-Flo
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • hot_rod
    hot_rod Member Posts: 22,256
    I have a dual coil HeatFlo on my solar thermal system, a great performer.

    I like the large smooth coil in the HeatFlo about 1/2 the pressure drop of the Alliance. Nice company, HeatFlo.

    On the Alliance, the removable coil is nice as they do lime up. Cement lined tanks can last 30 years, and they hold heat a long time.

    A toss up.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Solid_Fuel_Manbob eck