Cya and fc

[lwilbanks]

i am a new pool owner by purchasing a home with an existing above ground pool. 15 x 30 and 4' deep. i don't know how to balance my PH, cya and fc. I have the super shock bags and the 3" chlorine tablets. I also have PH up and ph down and a large bag of baking soda. Here are reading i've taken after thouroughly cleaning pool and running filter for at least 24 hours. Thanks in advance for your help.

Hardness = 0

FC = 0

PH = 6.4 - 6.8

TA = 40

CYA = 0

[chem geek]

You first need to get yourself your own good proper test kit, either the Taylor K-2006 or the TFTestkits TF-100. It is very doubtful that your fill water had zero CH unless it went through a water softener.

The super shock bags are either Dichlor or Cal-Hypo. If you would read the ingredients on the bags that would be helpful. If they are Dichlor, then that will let you add chlorine and Cyanuric Acid (CYA) at the same time. If they are Cal-Hypo, then that would let you add Calcium Hardness (CH) at the same time, though with a vinyl pool you don't need to increase your CH level (at least not much). Keep the following rules in mind since using those chlorine tabs (which are Trichlor) will increase the CYA level over time.

For every 10 ppm FC added by Trichlor, it also increases CYA by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases CH by at least 7 ppm.

You can read the Pool School for additional information on how to get started, but right away add some chlorine to the pool so probably using the super shock bags, but not too much. You can use The Pool Calculator to calculate dosages if you know what it is you are adding.

The baking soda will increase the TA level, but as for what level to set that depends on whether you will be using only Trichlor pucks/tabs.

[Guest]

thanks for your help. The super shock bags are cal hypo. I also inherited a pail of Blue Wave stabilizer. I don't know what it's for. The 3" tablets are trichlor, i think. Is it the chlorine that makes pool water crytal clear? Thanks again for your help.

[Guest]

do you have any idea how many gallons are in this 15 x 30 above ground pool that is 4' deep all around?

[RobertW]

1 ft ^3 = 7.48 gallons

15 x 30 x 4 = 1800 ft^3 x 7.48 gal/ft^3 = 13464 gallons

[chem geek]

thanks for your help. The super shock bags are cal hypo. I also inherited a pail of Blue Wave stabilizer. I don't know what it's for. The 3" tablets are trichlor, i think. Is it the chlorine that makes pool water crytal clear? Thanks again for your help.

"stabilizer" aka "conditioner" is Cyanuric Acid (CYA) though it should say that on the ingredients. You can use it to raise your CYA level initially, but probably not above 30 ppm if you plan on using Trichlor pucks/tabs since those will continue to increase the CYA level as I had indicated earlier. Use The Pool Calculator link I gave you earlier to calculate dosages.

Yes, it is chlorine that makes/keeps the water crystal clear (you can see my pool here at day and here at night). However, if you continue to use stabilized chlorine such as Trichlor, the CYA level will rise (unless you have a LOT of water dilution) and that will lower the active chlorine level unless you proportionately raise the Free Chlorine (FC) level to compensate. It is the FC/CYA ratio that determines the active chlorine level that prevents algae growth and determines the rate at which bather waste is oxidized and pathogens are killed. I suggest you read the Pool School link I gave earlier to learn more about the chlorine/CYA relationship. If you are only going to have your pool up for just a few months, then using Trichlor pucks/tabs will probably be OK if you raise your FC target as you go along or if you use a supplemental algaecide (e.g. PolyQuat 60) at extra cost. However, the least expensive approach is to use chlorinating liquid or bleach, though you'll need to add it to the pool every day or two unless you have a mostly opaque pool cover.