changing pool water

[chem geek]

Dan,

It sounds like you have fill water that is high in Calcium Hardness (CH) and that you have a lot of evaporation and refill which increases that CH but don't have a lot of dilution from rain overflow or from backwashing (perhaps a cartridge filter?). Do I have that right?

You did not write about your other water chemistry parameters such as pH, Total Alkalinity (TA), Cyanuric Acid (CYA) and usual water temperature. It would be helpful to know those number as well.

Your water clearly has a high saturation index (which you can calculate using The Pool Calculator) so is producing scale. My concern is that this scale may not only be at the tile line, but also in your gas heater (if you have one) and even in your pipes, filter, pump and other components.

Have you been using any kind of calcium metal sequestrant or anti-scaling product? I think it would have been wise to be diluting your water some every year to try and keep the CH to a more reasonable level to prevent scaling. You may also consider getting a pool cover to prevent evaporation as that, plus subsequent refill, is likely the primary cause of the rising CH. If you didn't want to heat the pool too much (say, in the desert or other hot environment), you could use an opaque white or reflective cover instead of a standard blue or clear bubble-type cover.

If you do a water replacement, be careful of your water table and the kind of pool you have (plaster, fiberglass, vinyl; in-ground, above-ground) as you can damage the pool from a full drain. If this is your situation, you can either do multiple partial drain/refill or can use the large sheet or multiple silage bag method for water replacement.

Richard

[boscoe]

Richard,
thanks for the reply. Yes, it is a cartridge filter here in Arizona. I am goung to fill out and post the pool calculator results later today. I went to a pool supply store with a sample and was told that my chlorine was .5, ph was 7.8, and alkalinity was 200 and there was no stabilizer at all. They advised to drain the pool and refill it in November because of the extreme summer heat here. I purchased a new complete test strips kit and tested the water. Surprisingly, the stability showed to be safe. I'm not sure if sombody elses pool water sample was being used.
Dan

[boscoe]

Richard,
thanks for the reply.
Yes, we do have a pentax cartridge filter with 4-3" cartridges. We cleaned them after a year and are starting a 2 month cleaning routine. Before cleaning them our readings were as follows:
hardness-1000, total chlorine-5, free chlorine-3, ph-7.8, total alkalinity-240 and cyanuric acid-300 with aquacheck select test strips. Its 9000 gallons with a heater and has pebbletec lining.
We rarely get rain here in Arizona. We have never used any anti scaling products because I can't find a reliably reccomended product I have faith in.
I drained 800 gallons a day reducing the level about 4" every day allowing the make-up water refill it for a week before my little giant transfer "pony" pump broke. The cyuranic acid came down a bit to the maximum 300 reading.
The pool is too big for a cover. I am considering using the chlorine tablets as needed until it gets cooler in November and draining it half way with a commercial pump (3000 gph) and refilling it. I stopped adding the tablets to the skimmer and now fill the dispenser and we are holding the chlorine at the ok level for almost a week.
What is a multiple silage bag method?
Will there be any harm in just using more chlorine with the high cyanuric acid level until November?
The water is about 4 years old.
Dan

[aylad]

You can try using more chlorine, but you're going to have to keep it in the 8-10 ppm range at all times (that's for 100+ CYA), and even that may not be enough. It might help if you use some polyquat 60 as well. No guarantees, but I guess it's worth a try. You do need to stop using the tablets, though--they are raising your stabilizer even higher and soon the CYA will be too high to compensate for even with high chlorine--if you're not at that point already.

Janet

[boscoe]

ok, I'll try the polyquat60.