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Thread: Iron Stain / Ascorbic Acid Frequency

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    hoskim's Avatar
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    Iron Stain / Ascorbic Acid Frequency

    Applied / spread ascorbic acid once first two months (of opening). Since then AA treatment almost every week due to brown / iron staining, and wondering what's going on as nothing significantly changed. I even took the pool light out, cleaned out the niche (was pretty dirty and this may be causing some mustard algae which is another story - if you are going to remove your light, please have your vacuum ready-to-go before dead / live algae spreads), and currently soaking screws in vinegar / AA to remove any rust.

    FC 1.0 (will increase / go through SLAM then Mustard Algae treatment)
    pH 7.0 (had to lower TA and aerating a bit)
    TA 75
    CH 50 (but vinyl pool)
    CYA 70
    Borate 40

    Not sure why iron staining is occurring so frequently...went through 10lb of AA this season already and looks like another 10lb until closing (mid-Sept??).
    I did read on a TFP board that I should not increase FC dramatically once I go through AA treatment so I did so..in fact, was going through the process of slowly increasing FC but this occurred again.


    Any insights? (oh...have Culator and poured in 2 qt of Jack's Magic Purple 2 weeks ago)
    25,000 Gal, in-ground w/ vinyl liner
    Hayward SP2303VSP (1.5 HP) / DE filter (4820)
    Aqua Rite SWG / T-CELL-9 (v1.5)
    Polaris 380, PB4-60 Booster Pump (post-2012) / Aqua Heat Pump (S95)
    TF-100 Test Kit with Speedstir

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    Re: Iron Stain / Ascorbic Acid Frequency

    Are you refilling from a well? If so, that is the source of continuing additions of iron.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Iron Stain / Ascorbic Acid Frequency

    Thanks for the feedback. No refilling at all and actually drained a bit after some rain. We have no access to well.
    25,000 Gal, in-ground w/ vinyl liner
    Hayward SP2303VSP (1.5 HP) / DE filter (4820)
    Aqua Rite SWG / T-CELL-9 (v1.5)
    Polaris 380, PB4-60 Booster Pump (post-2012) / Aqua Heat Pump (S95)
    TF-100 Test Kit with Speedstir

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    Re: Iron Stain / Ascorbic Acid Frequency

    What do you think is the source of iron?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    hoskim's Avatar
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    Re: Iron Stain / Ascorbic Acid Frequency

    I have no clue...not sure whether pH, TA (had high TA of 110) and/or Borate (added 1 month a go) cause this...
    25,000 Gal, in-ground w/ vinyl liner
    Hayward SP2303VSP (1.5 HP) / DE filter (4820)
    Aqua Rite SWG / T-CELL-9 (v1.5)
    Polaris 380, PB4-60 Booster Pump (post-2012) / Aqua Heat Pump (S95)
    TF-100 Test Kit with Speedstir

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    Re: Iron Stain / Ascorbic Acid Frequency

    pH, TA can cause the iron to precipitate but to solve your problem you need to find the source of the iron. I think you can get a water report from you city supplier or maybe even ask them for an iron test at your location.

    Do you have a whole house softener?
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    hoskim's Avatar
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    Re: Iron Stain / Ascorbic Acid Frequency

    I do not have filter / water softener system in my house.....the only suspect is somewhat of high TA (of 110)....dumping AA more often (1-2 lb a week)...
    25,000 Gal, in-ground w/ vinyl liner
    Hayward SP2303VSP (1.5 HP) / DE filter (4820)
    Aqua Rite SWG / T-CELL-9 (v1.5)
    Polaris 380, PB4-60 Booster Pump (post-2012) / Aqua Heat Pump (S95)
    TF-100 Test Kit with Speedstir

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    Swampwoman's Avatar
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    Re: Iron Stain / Ascorbic Acid Frequency

    Hoskim, what sequestrant are you using when you perform the AA treatments?

    I ask because some metal sequestrants don't work well in the "high TDS" environment of swg. For this reason, those on swg should use jacks magic purple, which is specifically formulated to work in a salt pool. Give that a try and be sure you're adding a full start up dose, not a maintenance dose, after your AA treatment.

    With respect to the origin of the iron, it is possible that trace amounts are coming from the salt itself...if there are trace amounts from the salt and trace amounts from municipal water, plus the electrolysis process of swg, you have a formula for frequent staining. It will help to control your ph (eg if possible, keep it low ish - eg 7.2-7.4) or at very least not let it get past 7.6.

    If you are using and maintaining the right kind of sequestrant, and controlling your ph and still get staining weekly then you'll need to dig a little deeper and get both pool and source water tested for iron, inspect the pool for any corrosion, and consider additional plans such as prefiltering your source water and possibly adding an inline zinc anode if there's corrosion.

    But first, lets make sure you're coming out of the AA treatment correctly with sequestrant, and that you're adding maintenance doses and controlling ph.
    In ground extended Grecian, 22,000 gal, Hayward 220t sand filter, vinyl liner, dolphin m4 supreme.
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    Re: Iron Stain / Ascorbic Acid Frequency

    Thanks and that's very insightful. I will try to keep the Ph low. The funny thing is I only used the Purple Stuff and I thought that may be the reason Being frustrated with the frequency, I recently added a bottle of Kem Tek (still have 1 1/2 bottles of Purple Stuff as well) which seemed to help but not much. In any case, your last sentence of "But first, lets make sure you're coming out of the AA treatment correctly with sequestrant, and that you're adding maintenance doses and controlling ph." makes perfect sense - unfortunately (or fortunately?? ) we will likely close our pool within next 2-3 weeks.
    25,000 Gal, in-ground w/ vinyl liner
    Hayward SP2303VSP (1.5 HP) / DE filter (4820)
    Aqua Rite SWG / T-CELL-9 (v1.5)
    Polaris 380, PB4-60 Booster Pump (post-2012) / Aqua Heat Pump (S95)
    TF-100 Test Kit with Speedstir

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    Re: Iron Stain / Ascorbic Acid Frequency

    Silly question but what color is the dirt around the pool? Also, do you know what the heat exchanger is made of in your heat pump?
    Bob - Palm Beach by San Juan Pools. approx 5000 gals., Pentair 320 cartridge filter (all new guts installed by me), Goldline SWG, 'New to me' Kreepy Krauly Sand Shark, Intermec 104 Timer Test kit: TF-100 w/Speed Stir

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    hoskim's Avatar
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    Re: Iron Stain / Ascorbic Acid Frequency

    Brown..they are iron stains as they disappear immediately after applying AA. Dont know about the heat exchanger as i dont use it but will look. The funny thing is that this happened recently. Nothing in june and july
    25,000 Gal, in-ground w/ vinyl liner
    Hayward SP2303VSP (1.5 HP) / DE filter (4820)
    Aqua Rite SWG / T-CELL-9 (v1.5)
    Polaris 380, PB4-60 Booster Pump (post-2012) / Aqua Heat Pump (S95)
    TF-100 Test Kit with Speedstir

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    Re: Iron Stain / Ascorbic Acid Frequency

    The reason I ask about the dirt, is I recently found out that in places where the dirt/clay is red, it's usually from iron in the ground. But since you are brown dirt, that's not it.
    My exchanger was made of iron and it was rusted. I didn't know that and when I tried to get it going I dumped a couple of pounds of rust into the pool. I cleaned it all out, but the damage was done.
    Bob - Palm Beach by San Juan Pools. approx 5000 gals., Pentair 320 cartridge filter (all new guts installed by me), Goldline SWG, 'New to me' Kreepy Krauly Sand Shark, Intermec 104 Timer Test kit: TF-100 w/Speed Stir

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    Re: Iron Stain / Ascorbic Acid Frequency

    The funny thing is that this happened recently. Nothing in june and july
    Have you had your lawn fertilized recently? Fertilizers also contain trace amounts of iron, just so you know. Also, you might want to take a peek inside your heat pump to see if any corrosion has developed...even if its turned off, if there's water running through it and any iron parts it could in theory become a source, in which case an inline zinc anode might help.
    In ground extended Grecian, 22,000 gal, Hayward 220t sand filter, vinyl liner, dolphin m4 supreme.
    If TFP has helped you, please click to SUPPORT TFP!
    Helpful Links:
    GET A TEST KIT Chlorine/CYA Chart How to SLAM About Metals & Stains

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    hoskim's Avatar
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    Re: Iron Stain / Ascorbic Acid Frequency

    A great point. Fertilizer yes and will take a look at the exchanger.
    25,000 Gal, in-ground w/ vinyl liner
    Hayward SP2303VSP (1.5 HP) / DE filter (4820)
    Aqua Rite SWG / T-CELL-9 (v1.5)
    Polaris 380, PB4-60 Booster Pump (post-2012) / Aqua Heat Pump (S95)
    TF-100 Test Kit with Speedstir

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