Open Forum

Best Water Treatment for Closed Loops

  • 1.  Best Water Treatment for Closed Loops

    Posted 03-23-2017 23:17
    What is the best water treatment for closed loops when using propylene glycol?  Deionized water? Deionized water with anticorrosion additives? 

    I see loop solutions in existing loops that are murky and corrosive to cast iron pump bodies.  Using a 1 micron filter does not take all the murkiness out.  Perhaps I need to research what the hydronics industry does for water treatment.

    Douglas Wall

    Wall Geothermal
    Guthrie OK

  • 2.  RE: Best Water Treatment for Closed Loops

    Posted 03-24-2017 11:18
    The 2016 Design and Installation Standards includes a new section on water quality & treatment.  I highly recommend reading through Section 3 - specifically Sections 3B, 3C and 3D.  

    Ryan Carda
    Geo-Connections, Inc.

  • 3.  RE: Best Water Treatment for Closed Loops

    Posted 03-27-2017 14:44
    Douglas:  As per Ryan the latest IGSHPA standards in section 3 are a great starting point.  An initial water test should be done to identify constituents, pH and if you have any biogenic activity going on (which can also impact corrosivity and pH).  Another thing I like to determine is run the water test report by the antifreeze vendor or manufacturer to make certain there is nothing in the water that can react with the specific propylene glycol composition, which can sometimes be related to temperature and % volume, where precipitates or scaling can form as a result of a miss-match of water and antifreeze chemistry.  It's rare but we have experienced it before on some of our light commercial and 'trophy' home installations.  One of the other things I do when diagnosing a problematic loop fluid situation is ask the PG vendor what to test for, and explain the nature of the system to the water treatment lab so they do not make assumptions on what to test for. Many of these guys have no idea that we do not use a boiler or cooling tower and a loop system is a true closed loop; it can help to educate them what your anticipated EWT range is, as temperature can influence some types of chemical reactions.

    If your system does have 'bugs' (bacteria) digesting the PG and excreting contaminants - the loop water might have a vile, foul sulfurous smell - you will want the water test to focus on bad things resulting from bug growth.  I am no expert but most of the water chemistry gurus I have dealt with typically recommend a nitrite active ingredient inhibitor for corrosion, and a glutaraldehyde microbicide inhibitor for bad bacteria, but there are plenty of other inhibitors to address specific problems.  Concentrations may vary depending on the situation and level of corrosion/bacterial activity.  In extreme cases it may be necessary to shock the system with a stronger dose, or even flush the system to clean it out and start over.

    One other thing to consider is that different metals favor different pH ranges.  What works for steel piping systems may not get along with any aluminum components for example.  So verify your above ground design has compatible metallic items from a pH requirement perspective.. Thankfully HDPE making up a ground loop is pretty much inert to most any antifreeze or inhibitor cocktail.

    [Terry] [Proffer] [Geothermal Manager, CGD]
    [Major Geothermal]
    [Wheat Ridge] [CO]