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Thread: Question about the need for calcium in vinyl pools

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    stev32k's Avatar
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    Question about the need for calcium in vinyl pools

    I'm wondering why calcium is needed in a vinyl lined pool. I can understand why it's needed in a plaster, concrete, or tile lined pool, but don't understand the need when the pool is vinyl lined.
    20' x 40' IG with vinyl liner volume approx. 35,000 gal.1.5 H.P. main pump, Polaris 280 cleaner W/ 3/4 H.P. booster pump
    Hayward sand filter, 3.14 sq ft, 62 gpm. Stenner 45 MPH10 chlorine feed pump. 1 micron final filter bags (home made and very effective)

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    JasonLion's Avatar
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    Re: Question about the need for calcium in vinyl pools

    Calcium isn't really required in a vinyl pool. We set the recommended minimum level at 50 for vinyl pools because we don't have enough experience at levels below 50 to be sure that it is completely trouble free. But as far as I know you don't actually need any calcium at all.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Question about the need for calcium in vinyl pools

    Its recomended to have some calcium in a vinyl pool for a couple reasons. Water that is too soft can be corrosive to metal. This could have an adverse effect on metal that comes into contact with the pool water such as ladders, rails, and most importantly heat exchangers in pool heaters. Most manufacturers have a hardness requirement for the warrenty.

    Now, all that being said, I've worked on copper piping in 40+ yo houses where I know the water was pretty soft (< 50 ppm) and I've yet to see real problems with corrosion that I would have attributed to soft water. I've also heard that elements that make up the vinyl could start to leach out if the hardness level was too low. But, I have seen no real proof or study that this is true, so take that with a grain of salt.
    Bottom line if you have a heater, run 100 ppm or so. I keep mine around 100 ppm. Thats enough, IMO, to negate any negative effects on my heat exchanger, but low enough not to worry about scaling and coating my SWG with calcium. Even if I did not have a heater, I would still keep ~100 ppm.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    spishex's Avatar
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    Re: Question about the need for calcium in vinyl pools

    If you want some good reading regarding metal corrosion, here's a brief discussion and here's a longer, more contentious one.

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    Re: Question about the need for calcium in vinyl pools

    Quote Originally Posted by spishex
    If you want some good reading regarding metal corrosion, here's a brief discussion and here's a longer, more contentious one.

    Ok, that made my head hurt! All i know is a lot of heaters have a warrenty based on having some hardness in the water. So, if you have a heater, put some in
    I didn trealize this was so controversial!
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    stev32k's Avatar
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    Re: Question about the need for calcium in vinyl pools

    I don't have a heater and (I think - but not positive) the only metal in contact with the pool water is the ladder at the deep end, the underwater light fixture, and the screws holding the returns in place and all those are 316 stainless. The pump casing and impellers are plastic and all the piping and valves are PVC. I'm not sure about the filter internals. The distribution laterals may be some sort of stainless (hope they are not carbon steel).

    I keep the the TA between 90 - 120 and the pH has been very stable between 7.4 - 7.6 (since I quit using the cheap Wal-Mart bleach). The reason I asked the question is that the CH has dropped to 30 as a result of heavy rains and I was trying to decide if it is worth the cost of the chemical to bring it back to the 50 - 80 ppm range.
    20' x 40' IG with vinyl liner volume approx. 35,000 gal.1.5 H.P. main pump, Polaris 280 cleaner W/ 3/4 H.P. booster pump
    Hayward sand filter, 3.14 sq ft, 62 gpm. Stenner 45 MPH10 chlorine feed pump. 1 micron final filter bags (home made and very effective)

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    JasonLion's Avatar
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    Re: Question about the need for calcium in vinyl pools

    Calcium, or lack of calcium, has no meaningful impact on metal corrosion in swimming pools. The kinds of metals used in pool construction are all safe at any calcium level. Metals are far more sensitive to the PH and FC levels. If PH is way too low or FC is way too high you are very likely to see metal corrosion, regardless of the calcium level.

    One issue with extremely low calcium levels is foaming. Calcium levels at 100 or higher will suppress most foaming. Still, foaming is quite rare even at very low calcium levels unless you have hot tub style air jets or accidentally get some soap in the pool. If you have a connected spa with air jets, or experience foaming from a waterfall or other water feature, you should keep the calcium level above 100.

    Heater warranties are an issue. The heater it's self doesn't care how low the calcium level is, but you don't want to give them an excuse to not honor the warranty. If you have a fairly new heater you should check the manual to see what calcium levels they call for.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Question about the need for calcium in vinyl pools

    I have never added calcium to my liner pool. I don't think the previous owner did either. The liner lasted 12 years. My heater, a Hayward H300E is 10. My rail, ladder and dive stand are all rust free.

    I do add it in F/G and plastered pools.

    I don't add it in painted pools.

    Scott
    Owner of - PoolGuyNJ LLC
    Expert Pool and Spa Repairs, Renovations, and Augmentation. Helping people decide what is the right gear for meeting their needs. Expectations Set, Expectations Met, No Surprises.

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    Re: Question about the need for calcium in vinyl pools

    An inexpensive way to raise the calcium level is to use Cal Hypo as a chlorine source for a few weeks. Cal Hypo is a very cost effective source of chlorine. With a liner pool, there should be no problem in taking a few weeks to raise the calcium level. This is what I do.

    Standard warnings about dissolving Cal Hypo apply. Monitor the calcium level twice a week and switch back to liquid chlorine or SWG when the calcium level is where you want it.
    11x27 in ground, vinyl pool
    ~12,500 gal
    PAC FAB (Pentair) Pinnacle 3/4 hp pump
    Pentair 24 sq ft DE filter
    One skimmer, one return (no main drain)

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    Re: Question about the need for calcium in vinyl pools

    Be careful about adding Cal-Hypo to a vinyl pool. It doesn't dissolve that well so you need to be particularly careful to brush the area where you add it to ensure thorough mixing. Pre-dissolving it in a bucket of water can help as well. You don't want chlorine settling and bleaching out a part of the liner.
    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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