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Fc And Cya Levels


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#1 Anka

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Posted 05 June 2006 - 09:39 AM

We have a 12,000 gal a-g pool which uses 3" trichlor tabs through an inline feeder. The feeder is set to 1/2. I test the water daily with AquaCheck strips and a 4-in-1 reagent kit.

I had some trouble at the beginning of the season with low pH readings, 6.8, but after slowly adding pHPlus I'm now at 7.4 pretty much. It reads 7.2 with the strip and 7.6 with the kit. Total alkalinity is between 80 - 100, depending on which test I use (strip or kit).

My problem is the FC and CYA. The trichlor, from what I understand, has the stabilizer in it and the feeder says on its lid to use only trichlor. The water is clear and feels smooth and silky, no problem there. Chlorine smell is minimal to none. My skin does not feel dry although my eyes burn a little.

The FC reading is 0 - .5 with the strip and 1.0 with the reagent kit. The 'standards' given by the test docs say I should have 1.5 to 3.0 free chlorine. The CYA reading is 0 on both tests.

I don't really understand why I can't get the FC/CYA readings to anything near 'normal' and yet the water is clean. Should I shock the pool to bring the Cl level up? Or should I just not mess with it on the premise that it ain't broke? smile.gif

We're new to pool ownership and maintenance and want to do it right because it's a pretty expensive toy.

Thanks for your input,
Anka
12,000 AGP, Pentair 2-speed pump, Hayward sand filter
Useful links: Pool Calculator AGP Issues

#2 waterbear

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Posted 05 June 2006 - 05:00 PM

Have you added any CYA to the pool. If you have not it will take a while for it to build up to about 30 ppm when your FC will begin to hold. You have 2 options:
1. suppliment your chlorine with liquid chlorine a few times a week until the CYA level is high enough and the FC is not getting burned off by the UV rays in the sun.
2. Add some CYA now to bring up the level...but this will bring you closer to a too high CYA level. When this happend you can drain and refill or stop using the puck and only use non stabilzied chlorine (liquid or cal hypo powder). When the CYA levels are very high you need to run your FC higher to compensate for the amount of CYA in the water 'stabilizing' your FC so there is enough to act as residual sanitizer.
If you are using a cartridge filter CYA levels can rise pretty fast. If you are using sand or DE the backwashing is always causing a bit of dilution so you can use the trichlor pucks for a longer time before trouble starts.
BTW, don't rely on the strips for more than a quick check to make sure your parameters are in line. If they are not the liquid reagent tests have a lot more precision which is needed when trying to balance the water. For example, most strips will tell you that you pH is somewhere between 7.2 and 7.8, but where? A good drop based kit ususally has the precision of .2 when testing pH.

I've tested more water than I ever care to think about!
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#3 Anka

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Posted 07 June 2006 - 05:14 AM

Thank you, Waterbear.

No, we haven't added any CYA and are really hesitant to do so. From what I've read on this forum, reducing an overload requires partial drainage and refilling. $$$$ sad.gif

I didn't know about adding liquid chlorine. Like Chlorox, you mean?


12,000 AGP, Pentair 2-speed pump, Hayward sand filter
Useful links: Pool Calculator AGP Issues

#4 waterbear

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Posted 07 June 2006 - 03:12 PM

QUOTE(Anka @ Jun 7 2006, 09:14 AM) View Post
Thank you, Waterbear.

No, we haven't added any CYA and are really hesitant to do so. From what I've read on this forum, reducing an overload requires partial drainage and refilling. $$$$ sad.gif

I didn't know about adding liquid chlorine. Like Chlorox, you mean?

Chlorox is not the best choice because they put some other stuff in it and it is not plain bleach. If you can find the Professional Ultra Clorox that is fine, that is the only one that the Chorox company recommends for swimming pool disinfection on their website but you will probably have to get it from a janitorial supply. Or get ultra bleach from walmart or some place like that. The cheapie ultra bleaches don't have the additive that is supposed to keep dirt from depositing back on your clothes in the washer. Ultra bleach is 6%, regular bleach is 5.25%, and pool store liquid chlorine is either 6%, 10% or 12.5%. If you use bleach you just have to adjust your dosage. They are ALL sodium hypochlorite!
I've tested more water than I ever care to think about!
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#5 Brulan1

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Posted 29 June 2006 - 11:59 AM

QUOTE(waterbear @ Jun 7 2006, 07:12 PM) View Post

Chlorox is not the best choice because they put some other stuff in it and it is not plain bleach. If you can find the Professional Ultra Clorox that is fine, that is the only one that the Chorox company recommends for swimming pool disinfection on their website but you will probably have to get it from a janitorial supply. Or get ultra bleach from walmart or some place like that. The cheapie ultra bleaches don't have the additive that is supposed to keep dirt from depositing back on your clothes in the washer. Ultra bleach is 6%, regular bleach is 5.25%, and pool store liquid chlorine is either 6%, 10% or 12.5%. If you use bleach you just have to adjust your dosage. They are ALL sodium hypochlorite!

Clorox is like 2 -4 percent and liquid pool shock sold is 12.5-14percent. Just use pool shock and the chances that it has any detergent is 100percent. Do not use any detergent algacide even though the algacide might be in-expensive. Spend the couple extra bucks and do it right.

#6 waterbear

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Posted 29 June 2006 - 08:36 PM

QUOTE(Brulan1 @ Jun 29 2006, 03:59 PM) View Post

Clorox is like 2 -4 percent and liquid pool shock sold is 12.5-14percent. Just use pool shock and the chances that it has any detergent is 100percent. Do not use any detergent algacide even though the algacide might be in-expensive. Spend the couple extra bucks and do it right.

BOGUS INFORMATION!!!!!
Regular bleach is 5.25% sodium hypochlorite. Ultra bleach is 6 % sodium hypochlorite. Liquid chlorine is either 6% (SAME as ultra bleach) or 10% or 12.5% (usually sold as liquid shock). The higher the concentration the faster it loses strength so that 12.5 jug might only be around 8% by the time it goes into your pool after sitting for a week, while the 6% stuff will still most likely be 6% a month or so later! The only difference between any of them is the amount you need to add to get a given ppm of Free Chlorine. Rule of Thumb for dosing...1 gallon will raise 10000 gallons of water approx. the percentage of chlorine in the sodium hypochlorite. Thus 1 gallon of 6% will raise 10000 gallons about 6 ppm and 1 gallon of 10% will raise 10000 gallons about 10 ppm, etc.

There is no such thing as 'detergent algecide'. There are linear quats which foam (perhaps this is what you mean), polyquat which, IMHO, is the only algecide you should ever use, copper and silver based algecides which WILL cause staining if you have enough metal in the water to kill the algae, sodium bromide which will convert your chlorine pool to a bromine pool even if you add more chlorine (this effect is temporary), and inorganic ammonia compounds which form monochoramines to kill the algae. The last two types require the addtion of a lot of chlorine repeatedly for them to be effective and tend to create a lot of problems such as a hugh chlorine demand in the pool until they 'burn off' in a week or two.
I've tested more water than I ever care to think about!
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#7 Hatenderab60

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Posted 19 May 2007 - 07:50 AM

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