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Hard or soft: what water to feed into Hydronic heating system

smihailasmihaila Member Posts: 93

I'm currently installing a simple hydronic system at my house, using steel panel rads, Lochinvar WHN055 gas boiler, Grundfos Alpha 15-55 ECM pump, and copper piping. Using a direct feed (no hydraulic separation). No indirect DHW tank (since I have a separate Rinai RC98i tankless solely for that purpose).

My water is quite hard in my area (24 grains) and I have a brand new water softener delivering water for washing and the tankless water heater.

I also have a separate water line for drinking water, which is connected to an activated carbon filter device (backwashable, warrantied for 5 years) - to filter out the chloramine.

We haven't installed yet the water feed line for the Lochinvar.

Now, I have a big dilemma: which is the least worse water line to connect:

(1) Un-softened, with high limestone content, but not salty and without chloramine.

(2) Or softened water, but potentially a bit salty due to water softener's principle of operation (resin bed propagating a bit of salt in the water).

With option #2, I'm basically concerned that some salt concentration in the water may shorten the life of the steel panel radiators, rusting them on inside?

So, the dilemma is: limestone precipitates inside the hydraulic circuit, gaskets and thermostatic valves vs. salt in rads?

Thank you.


  • ZmanZman Member Posts: 3,476
    Truck it

    Lochinvar should have a water hardness number in the manual.

    Depending on the size your system, I think it would make sense to truck in a few 5 gallon buckets for the original fill.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • smihailasmihaila Member Posts: 93
    Do you mean

    that I should buy drinking water from a water store?

    Lochinvar max accepted figures for water hardness - can't recall them right now, but I know they are lower than what I have in my area.

    For any make-up water, would soft water be ok or it's still dangerous to use?

    Thank you for replying.
  • ZmanZman Member Posts: 3,476
    Tech Support

    I would check with tech support to get the definitive.The salt can be worse on the stainless than hard water.

    In the past we have just filled buckets with treated city water. I guess you could buy drinking water also

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Jamie HallJamie Hall Member Posts: 6,653
    I would go with

    purchased water.  Shouldn't take all that much, and in most places you can go down to the supermarket and buy bottled water in 5 gallon jugs for very little (you don't need Perrier, after all).

    The high TDS in the softened water will cause corrosion in your system, no question.  The high hardness in the raw water might cause scaling and reduced efficiency in the boiler.  I am puzzled, though, about the need to eliminate chloramines -- they may be present in low levels (quite harmless) in city drinking water which has been chlorinated, but they should not be present in a private water supply unless you have to chlorinate your private water for some reason.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • ChrisChris Member Posts: 3,056
    Add A Cuno/AquaPure

    AP430 at the cold water feed. Most cost effective way and simple..
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
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