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Community and Q&A

Lime in hydronic system

charlie_sullivan | Posted in Mechanicals on

Our low-temperature 9-year-old hydronic heating system, which uses city water in a closed loop with panel radiators, has been accumulating some kind of minerals in a sand-like form. They particularly collect inside the mini flow-meters built into a recently-installed Viega manifold, sometimes clogging them. Possible solutions I’ve considered include:

1. Flushing the system thoroughly.

2. Using some of the magic chemicals sold for hydronic systems, including cleaning solutions and lime-scale/corrosion prevention solutions.

3. Adding a dirt trap before the manifold to collect the debris without clogging the meters.

4. Refilling the system after flushing with trucked-in conditioned water instead of city water.

Does anyone have suggestions as to which of those are the best options, or which brand of chemical treatments is trustworthy? I’m guessing flushing plus chemicals is probably adequate, but I’m not sure how to tell the snake oil apart from the effective treatments. And I might want to install a dirt trap while the system is drained just to be sure.

It’s a water-water ground-coupled heat pump system, and the water exiting the heat pump is usually 100 F or lower, so it shouldn’t be a worst case scenario for lime deposition. It might be adequate to just flush it, but I don’t want to get into a cycle of flushing it, refilling it with fresh city water, and then having all the minerals in that water collect in those meters, prompting a need to flush it again. In retrospect, having the flow meters sticking up off the manifold rather than down would have been better, but that’s hard to change that now.

Thanks for any advice even though this isn’t really a green building question per se. My plumbers and my local water testing company had no suggestions to offer.

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  1. Anon3 | | #1

    No experience, but try Watts's ScaleNet, apprarently it can descale.

  2. DIYJester | | #2

    I generally deal with much larger scale systems, but I would think there would be a citric acid based cleaner that at the correct PH might, might, be acceptable for the system, which I'm guessing is PEX.

    You could also add strainers, a small RO or other systems to help keep the water cleaner. The solids generally tend to precipitate on the hotter areas such as the boiler or coils, so it may just be breaking free. The other possibility is that there is just a generally high amount of TDS, total dissolved solids in the system precipitating and concentrating out in the hydronic system.

  3. DIYJester | | #3

    I personally would always tend to stray electronic "chemical" treatment systems. I have personally dealt with one installed in my house prior to I moved in and also in a few different hospitals that destroy their condensate, DA tanks, and sometimes boilers. The one in my house did nothing in my experience. A water softener did wonders compared to the magnetic system that was installed. I still left the magnet in place, just in case the ions made a difference ;)

  4. Jon_R | | #4

    Just filtering it out make sense to me.

  5. user-2890856 | | #5

    Charlie, As far as cleaners and system conditioners go look at Fernox . Possibly install a TF1 filter (magnetic) while performing the cleaning . Just click on the product tab and continue .

    Attempt to locate someone who can supply or treat new water dependent on the route you take . Our systems as we have continued to learn all get filled with DM ( demineralized ) water now . Check out this publication , .

    Have that water tested to see what it contains , this is one of the biggest reasons besides lack of knowledge and / or believing you know The Laws for system and component failures .

  6. charlie_sullivan | | #6

    Thanks to Mike, Jon, Rich and Anon3 for the helpful input. Rich, I like the way you refer to lack of knowledge and believing you know as two sides of the same coin. I'll definitely read the Caleffi book: subtitle is "Water Quality in Hydronic Systems" for anyone else reading this. And I'll also look at Fernox products.

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