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want to install a domestic hot water system in a kitchen\laundry can't decide how to do it 4 on demand water heaters would do the job with a 119 gal storage tank water is very corrosive can't help but think that neither is going to last the way that you have to recirculate through the on demand water heaters and the tank will last for about 3 to 4 years also have 2 unit heaters in there  36000 btu each


  • SWEISWEI Member Posts: 7,356
    very corrosive

    is going to be a problem no matter what.  Do you have a water test?
  • smklinsmklin Member Posts: 46
    High TDS

    Yes the water is like high in sodium my tds reads in the high 3500 range
  • SWEISWEI Member Posts: 7,356
    mitigate that

    using RO or use an appropriate HX (titanium or a specialized stainless alloy.)

    I assume all the downstream plumbing is either polymer or stainless?

    What are the demand numbers?
  • GordanGordan Member Posts: 891

    Stainless might not like chlorides, either... pitting corrosion will occur.

    On a different but related topic, a neighbor just asked me to look at a problem he has with his Burnham Alliance A 40 indirect. The handhole cover and the mating portion of the tank, which are both fairly heavy gauge 304 (I think?) stainless, are exhibiting severe but localized pitting-type corrosion; a small section of the flange on the handhole cover simply crumbled off. He has well water which he says is acidic - his copper plumbing developed pinholes and he replaced it with PEX. I'm scratching my head trying to imagine why there would be such severe corrosion in a few spots, while the majority of the surface of the tank looks relatively pristine. I was suspecting stray currents but it seems unlikely that any electrical potential could exist between the tank and the cover, as they're connected by the clamp that seals the cover to the tank. Any ideas or suggestions as to the type of indirect that would be most resistant to this kind of corrosion, would be most welcome and appreciated.
  • Larry WeingartenLarry Weingarten Member Posts: 1,173
    Sounds like crevice corrosion

    Have a look here for a description.  Fixing it is a whole nuther  problem, though knowing what it is should help in finding an answer.

    Yours,  Larry
  • smklinsmklin Member Posts: 46
    edited November 2012
    Indirect or on demand

    Demand is about 150 gal per hour is that a decent choice or would a indirict be more the way to go don't know how long the on demand will last navien
  • SWEISWEI Member Posts: 7,356
    150 GPH

    At what temperature rise?  Is that the continuous demand?  What about first hour? 
  • SWEISWEI Member Posts: 7,356
    call GEA

    And ask them to spec you a brazed flat plate HX for this application.  I'm thinking their MPN series should work, since it's used for marine applications.  2.5 GPM at a 70F rise is only 87,500 BTU/hr so it won't be all that large.
  • ChrisChris Member Posts: 3,056

    Is not just chlorides. It is a mixture of calcium, phosphates, nitrates, sodium, potassium as well as chlorides. Need to take a water sample to a lab and have it tested specifically for chloride and hardness level.

    I wouldn't do on demand heaters. Condensing boiler and an Indirect and my choice would be dependent on the test results of that water..
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • GordanGordan Member Posts: 891
    Yes, after doing some research I had come up with the same conclusion

    Fixing it, it seems, would involve going back in time and showing that wiki to the product designer...
  • SWEISWEI Member Posts: 7,356
    Triangle Tube

    Just got an email from them confirming availability.  Drop me a line and I'll put you in touch with the PM.
  • Alley_SmithAlley_Smith Member Posts: 1

    yes it is somewhat difficult to apply but the plumbers can easily help you to install as small fault can lead to damage of the water damage system.
  • icesailoricesailor Member Posts: 7,265
    edited January 2013
    Corrosive water/location:

    Where is this well located? On or next to a farm that is close to the ocean?

    It sounds like a well with either salt water intrusion close to the ocean or a location next to a farm with prevailing winds off the ocean, covering the grounds with sodium chlorides. Or road salt run off.

    What is the depth to water from the top of the well head? What is the elevation above MSL (Mean Sea Level)? It should be on a septic plan. What is the depth of water to the bottom of the well casing? Is it a submersible pump? Does it have 20' of water above the screen?
  • smklinsmklin Member Posts: 46
    IN MT

    Located in north centreal Montana. It is a well 500' deep it is not just that well the geo maps for the area show the same type of water .I put in a TT with the 14 gal inderect tank in there was not quit enough so i put in navien before it to boost the temp.
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