changing pool water

[boscoe]

I was told that pool water should be changed every 5 yeras or when the calcium reached 1000 ppm. I have not had much of a problem cleaning the tile calcium every month before it binds too much but this year it seems to be accumulating more. The pool water is 3.5 years old now, always properly maintained chemically.
Its now 4000 ppm and and I would like to know what the ideal determining factor is for replacing the water and what, if anything, should be added to the new water when its changed,
Dan

[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.

[boscoe]

Well here is the outcome, I think.
My local pool supply store told me I needed to add stabilizer to the water as my Cyanuric Acid was gone. I added one cup to the 9000 gal pool that read 300 plus. Now that the level is too high and the water has been in it for about 5 years, instead of waiting until November to replace the water because although I have pebble tec lining its extremely hot here in Arizona and I want to avoid any chance of damage to it. I am using a pony pump to drain it slowly each day allowing the make-up fresh water feed to add new water to see if the acid reading it comes down. Do you think this might work?
Dan

[aylad]

This will work, albeit slowly--the new water should have 0 CYA in it, so by draining the old and diluting with fresh, the CYA reading will come down. Depending on the CH of your fill water, it should also bring your calcium down, as well.

Out of curiousity, how were you maintaining any chlorine in the pool with no stabilizer? I have a sneaking suspicion that the pool store gave you some wrong info.....

Janet

[Phillbo]

just for fun, last week I took a water sample to 3 different pool stores... and got 3 different results. whoda thunk it

[chem geek]

You should really get yourself a proper test kit. The best to get would be the Taylor K-2006. Most importantly, you need to get chlorine into your pool. Unfortunately, if your CYA level is now too high, you'll need a lot, but until you get your good test kit just add a bunch of chlorine to have at least 5 ppm FC or more which will max out your inexpensive test kit. Use The Pool Calculator to calculate dosages and check your water as the chlorine may get used up during the day or fighting algae.