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Thread: Phosphonic Acid - does it raise phosphate level?

  1. Back To Top    #1

    Join Date
    Apr 2009
    Burlington, ON, Canada

    Phosphonic Acid - does it raise phosphate level?

    Might be a dumb question, just based on the name, but if one uses a stain and scale treatment that has phosphonic acid in it, will this increase the phosphate level in the pool? I know phosphates don't matter etc. etc., I'm just curious as to where my phosphates came from. I've tested my rain and tap water and the test shows 0 for them.
    16x28 Roman, 55000 litres, salt water, Zodiac Duoclear 130 (mineral cartridge removed!!!), inground, vinyl liner
    Hayward Tri-star 1HP (1.85) pump, Hayward sand filter
    Nine Fafco Sunsaver 4x10 solar panels, Jandy LX 250 natural gas heater
    Jandy Aqualink PDA with Sub Panel Power Centre

  2. Back To Top    #2

    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: Phosphonic Acid - does it raise phosphate level?

    Phosphonic acid is a generic term that can refer either to the inorganic acid that will directly raise phosphate levels or to the organic acids aka phosphonates (such as HEDP) that are typically found in metal sequestrants. These latter compounds will slowly breakdown from chlorine and produce phosphates. This takes longer for HEDP which is one reason why we recommend metal sequestrants that use this compound. There are other phosphonates that break down more quickly and I experienced this myself as I described in this post.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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