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boiler fluid quality testing and strainer recommendations

schreibschreib Member Posts: 110
edited October 14 in Radiant Heating
I built my house 4 yrs ago and my plumbing contractor convinced me to allow him NOT to install a strainer in the hydronic system. His explanation at the time was they just cause unnecessary calls due to plugging. . . Based on the idea that he MAY be right being he does this all the time, I went with his suggestion. Just the same, it makes little sense to me being that contaminants can concentration and cause pumping problems, even with centrifugal pumps. Regardless, it is what it is.

I sampled the fluid, about 100 ml and found the Ph is about 8.1, but there is some sediment, whitish on the bottom. I found it took about 20 or 30 minutes for the entrained bubbles to bubble off. Figured I got this from the high pressure spurt from the system entraining air into my sample. sample color is light pink and at 50% concentration. I tested with my own refractometer. This is what it was originally, too.

I was looking for other experts point of view and what YOU do as normal in the installation and service of strainers in hydronic systems.

System: Wall hanging 55K Btu/Hr hot water boiler with a side arm hot water heater. 3 pumps: One for main water circulation in the secondary loop, one for primary loop(about 10 ft long to heat fluid in secondary directly) and one for the hot water loop.

Thanks for your assistance!


  • ZmanZman Member Posts: 6,002
    I am not convinced a strainer is needed on a properly constructed and cleaned new system.
    I like to also take small samples from boiler drains and other slow moving low points in the system just to see what kinds of things are settling out. If you are seeing significant debris in these places, it might make sense to install a strainer.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • EdTheHeaterManEdTheHeaterMan Member Posts: 798
    edited October 14
    Consider a strainer with a Magnet to remove iron oxides from circulating.
    I think Caleffi has one. Look up DirtMagPlus
  • schreibschreib Member Posts: 110
    hmmmm. I was not able to find a Caleffi video where the sound works but got the general idea. My impression is it is made for large residential systems, older design systems, systems with ferrous metals in them etc.

    I like the design with the two shutoffs and ability to clean off line though.

    My sample showed about 1/8" layer thickness of white particles(calcium?) that dropped to the bottom of my vial. My system is all PEX, copper, and the Lochinvar boiler is stainless. I am not expecting ferrous metal corrosion to any extent.

    Other suggestions?
  • hot_rodhot_rod Member Posts: 13,833
    For the cost, I would have both a high efficiency air sep, a microbubble type, and a dirtmag type. If you have an expansion tank, you have ferrous, so a dirt sep that can take small particles as well as any magnetite would be a good idea also

    ALL pex allows O2 into the system, how much depends on the quality of the pex and operating temperature. So at the end of the day all systems have the potential to have ongoing corrosion.
    Another option is to use a hydronic conditioner it protects the metals and buffers Ph. It will need an occasional boost as the O2 inhibitors will be depleted depending on how much O2 is entering.
    In reality system without any pex also get some O2 on and ongoing basis, around valve packings, pump or valve seals, nearly impossible to have an O2 free system.

    A combination DiscalDirtMag would give you the 3 critical functions in one component.

    Dirt, air and magnetite all contribute to lack of efficiency in boilers and heat emitters and constant wear on any moving part. It's easy enough to eliminate those unwanted variables.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • schreibschreib Member Posts: 110
    edited October 17
    I appreciate your input and if things get worse I will follow it. In the meantime. . .

    I brought in a local Plumbing company after turning away their 1st technician who had no clue about servicing boilers. . . Then they brought in the "pro" who was quite knowledgeable and agrees with Zman's suggestion that it is likely not necessary.
    When he sampled he got a Ph of 7.7, not as good as mine but still OK. Also, he got very little sediment as compared to mine. He pointed out that I failed to purge the sample point 1st of accumulation in that low area and he took it from higher up on the wall. He did not believe it necessary that after as clean as that sample was after 4 yrs I needed a strainer. So, for now, I won't be doing so.

    There is almost no Ferrous metal source either. The expansion tank is tiny, about a cubic foot or so Amtrol. I understand from the "pro" that you can now buy the same tank as non-ferrous plastic lined. He recommended to just keep up the maintenance of fluid at 7+ Ph and watch for pinholes in the exp. tank, replace with a newer, lined tank. At that point I would have virtually NO source of ferrous metal in the system. The stainless in the manifolds and fire tube is not likely to shed iron to any degree either.

    If I ever do become marginal on water quality the "pro" also suggested I look to a product called Fernox. Installed simply in a pressurized container it can be injected and work for years as an inhibitor to buffer the Ph if the built in glycol inhibitors have been exhausted to some extent.

    Finally, I already have a Spirovent, ,air only separator / remover. I notice like Caleffi, they also offer the 3 way(dirt, air, magnetic) separators.

    He also suggested I clean the fire tube a lot less often than I had been doing -- once / yr per Lochinvar. Now will move that out to once / 3 or even 5 yrs, but inspect through the window and condenser drain port each yr.

    Thanks for your suggestion; it is nice to have alternatives.
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