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Why are hydronic lines darker then DHW in combi boiler

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harry_fine
harry_fine Member Posts: 9
NTI combi boiler. Less than a year old. Runs great. Was wondering why on the closed system for the Carrier furnace heat, both supply and return, look like the water is darker.  Domestic hot water linea, same material, are white.  Do they fill the hydronic side with some sort of additive?

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  • Big Ed_4
    Big Ed_4 Member Posts: 2,785
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    Normally cold water pipes are darker in color ...

    There was an error rendering this rich post.

  • harry_fine
    harry_fine Member Posts: 9
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    So....why are the water lines to the furnace, same outside transucent white cokor pipe, darker in appearance. Is it just water inside?
  • GGross
    GGross Member Posts: 1,050
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    Yes the boiler water is likely very dirty. This can happen from many things, some are bad, some are not a problem at all. Unless a boiler system was recently filled with fresh water it is more than likely at least a little dirty in appearance.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,850
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    On a closed system, when you introduce new water (on first commissioning) that water acts like any water in an open system and starts to eat away at the ferrous metals in the system. As long as you do not replace that water, the agents that will rust and corrode the ferrous metal will eventually run out of the ability to eat away at the metal. Things like oxygen and other trace minerals will do their dirty work in a day or two, and that water is done. It has no more stuff in it that will destroy the metal. As long as you don't change the water, the little bit of discoloration from that initial surge of destruction will not continue and the boiler internal parts will continue to operate and circulate that water within the closed system over and over again without a problem. That water is now a little darker and will place the deposits throughout the system in trace amounts. That is why a semi clear tube will look a little dirty inside.

    On an open system, you are constantly replacing the water with fresh water that has not had the chance to work on the ferrous metals. That is because open systems must have non ferrous metal components. Glass lined tanks or stainless steel heat exchangers along with copper and brass pipes and fittings. And that water is constantly being replaced with fresh new water that hopefully is clean enough to drink.

    So what you're seeing is normal

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    Larry Weingarten
  • harry_fine
    harry_fine Member Posts: 9
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    Great reply. Thank you.