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Water chemistry and indirect tanks

dave123 Member Posts: 55
I'm looking at a particular SS indirect tank, that lists just two water requirements: pH 6.0-8.0, and chloride < 80 ppm. Doesn't mention water hardness. My city's water analysis lists pH 8.5 though, along with chloride 18 ppm and total hardness 99 ppm (4.6 gr/gal).

So overall, my city water is pretty good on hardness and chloride, but high in pH. I'm guessing that makes it prone to scaling, leading to the manufacturer's restriction?

I realize probably no one outside this site pays attention to these little things, but I believe in prevention of problems whenever possible. Is this the sort of thing to lead to early failure of the tank? And I assume it would void the warranty?


  • Larry Weingarten
    Larry Weingarten Member Posts: 2,295
    Hi,It couldn’t hurt much to call the manufacturer and ask about the pH and warranty. Seems to me that it would not damage the tank like salt or low pH would. Higher pH would actually benefit a glass lined tank.

    Yours, Larry
  • dave123
    dave123 Member Posts: 55
    I can't imagine though they'd ever say it was okay to not conform to their own install instructions. Seems like if a pH of 8.5 were really okay, the manual would say that.

    Though how one can make their tap water more acidic, I'm not sure. Doesn't sound easy.
  • mattmia2
    mattmia2 Member Posts: 4,017
    It is a combination as well. Soft water that is more basic has less mineral to precipitate. Water with a high sodium content is a lot more of a problem at 160 degrees than at 120 degrees. When you specify a single number you don't account for the fact that it is a system where all the pieces of the chemistry and the operating conditions interact. You can shop around for different manufacturers that use different alloys and are willing to tolerate different levels of risk on their warranty that might meet your conditions.
  • hot_rod
    hot_rod Member Posts: 15,070
    Since the Flint debacle, there seems to be a movement towards elevated Ph in public water supplies. Here is an example from Denver water.

    I understand the motive to protect piping from leaching, but coating heat exchangers like tanks, indirects, plate and tube and shell Hxers needs to be monitored also.

    Artificially adjusting the ph may not be the same as high mineral content causing the elevated ph? A bit above my water knowledge. pool water ph is easily adjusted up and down with common treatments, soda ash or acid.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Jamie Hall
    Jamie Hall Member Posts: 17,190
    As @mattmia2 said, it's the combination of parameters. I'm not going to second guess the manufacturer, but... that said, what you are quoting is pretty good quality water. With stainless steel, the number one villain is chlorides -- and you are nicely low on that. The combination of pH and hardness is what is related to scaling, particularly at higher temperatures (like an indirect!). Would you have a problem? Don't know, nor what the time scale would be.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • dave123
    dave123 Member Posts: 55
    There's a few other SS tanks listing the same pH 6-8 requirement. Guess I'll look at other alternatives.