High alkalinity, cloudiness

[Mr. Coconut]

I recently had a little rust spot fixed in my pool, which meant draining and refilling the pool. The water I get from my well is pretty good, but has high alkalinity and surprisingly little calcium. Since I refilled the pool, I've had the water tested by three stores -- all of them giving me different values, but along the same lines -- as well as testing it myself. Total alkalinity is around 180; PH is around 7.6; Calcium hardness around 220. CYA is around 80. The store I usually go to suggested adding about 4.7 gallons of muriatic acid to lower the alkalinity. I'm not sure why they'd want me to dissolve my walls (marcite on shotcrete), but I thought it best to ignore that piece of advice. The high alkalinity does result in a constant creeping up of my PH, though. Every time I have it nicely balanced, the PH travels up, and then I have to lower it again -- even without adding chlorine or anything else, the PH will move upwards. What would be the proper way of getting the TA to a more acceptable level without lowering the PH to some hideous level?

On a related note, the store suggested that I try shocking with Cal-Hypo for a change -- I usually stick with liquid chlorine -- since it will slowly bring the hardness up a little. That made some sense to me, but as soon as I did that, the pool went from absolutely completely clear to cloudy. Is that normal? It bothers me.

For completeness, this is a 24,000 gallon shotcrete/marcite pool from 1976 in South Florida.

 

[Richard320]

This article tells you how to reduce TA. It works. I run the spa jets full blast and run all my water through the spa when I need to aerate.

Why add Calcium? 220 is plenty high, but not so high you need to wory about scaling. I suspect that once you give it all time to dissolve completely and get the pH correct, your water will get clear again.

 

[JohnT]

Welcome to TFP!

There is an article here about lowering alkalinity.

You are right to be skeptical of the single-shot muriatic dose. It won't work in the long run, and it can damage your pool.

Remember that TA will vary with pH, so that two TA reading at different pH may both be accurate.

But it may not be worth worrying about. If you live where you get off-season rain of any significance, you might be able to just deal with the climbing pH and it will lower over time.

My fill water is almost 500ppm TA, so I'm well acquainted with high alkalinity. My pool isn't open yet, but I expect it to be below 100ppm when I open.

I just stayed on top of the pH and kept it in the lower part of the range. TA dropped steadily.

 

[JamesW]

If we assume a temperature of 80 F, then your CSI is +0.26. That's why the calcium hypochlorite clouded the pool more than usual. Calcium hypochlorite clouds the water anyway, but it does it more when the CSI is positive. I recommend against using calcium hypochlorite or sodium carbonate. Liquid chlorine is the best thing to use.

For a concrete pool without a salt water chlorine generator, I recommend a CSI of between 0.0 and +0.3. You can use the pool calculator to calculate your CSI. What is the water temperature?

If you just drained and refilled, it seems odd that your cyanuric acid is 80 ppm. Is that accurate? Did you drain all of the water, or just part of it?

 

[lightingguy]

I'll +1 the advice above.

Keep in mind while TA acts as a PH buffer it also can steadily raise your PH through carbon dioxide out gassing.

As mentioned - the act of keeping on top of your PH will steadily lower your TA and you can speed up the process by manually raising your PH with aeration.

 

[Mr. Coconut]

I appreciate the advice, thank you all. I will have to see if I can get the jets of air to work -- they never have before. Like I said, I usually stick with liquid chlorine and only tried the cal hypo to add a little calcium, but I will not be trying that again soon. It took two days for the pool to be clear again. But I'll be diligently lowering that TA and running the spa jets. Out of curiosity, how rapidly does PH rise with aeration?

The mystery of the CYA is easy: after refilling the pool, I added stabilizer to bring it to around 80. Any less just means chlorine breaks down far too fast.