Persistent low pool pH

[mdcbk]

My in ground gunite pool is 10 years old. I've always been able to manage water balance using trichlor tablets, bleach, acid, and washing soda, most of which I learned here long ago. This summer, I've not been able to keep the pH levels above 7. I've used so much washing soda in the past few months that the people at the grocery store are starting to look at me strange. Alkalinity is 120-180 usually. Cya is on the high side 100-150. Hardness is about 100. Our neighborhood switched to chloramine treated water last fall, and I'm beginning to wonder if that's contributing to the problem. It's also been extremely hot, > 90 for weeks, but that's not unusual in Texas. I thought about partial draining and refilling, but only want to do that if absolutely necessary, since we're in a drought and the water bill from just maintaining the water level is almost as high as my electric bill. Any suggestions?

[PoolDoc]

I'm leaving for the weekend -- my wife has been glaring at me -- so very briefly:

+ Stop using trichlor; use bleach
+ Read the Best Guess page, linked in my signature
+ Get a Taylor 2006 or 2006C (link in sig) from Amazon -- but if seller is not "Amato Industries" wait a day and order when they've restocked.
+ Chloramine fill water is not your problem
+ Use borax -- whatever it takes -- to cycle your pH above 7.0, but stop with the washing soda.
+ Read http://www.poolsolutions.com/gd/lowering-swimming-pool-alkalinity-step-by-step.html for UNDERSTANDING, but don't try to dupe the process there.
+ Instead, raise your pH to 7.0, then let it drift down to below 7.0, then repeat WITH BORAX
+ Let us know what the results are after a week; include K2006 test results. Test your CYA with a 1:1 dilution of pool water to grocery store distilled water.

[mdcbk]

Ok, using borax, the pH is sticking between 7.2 and 7.4. I've been using bleach rather than trichlor and have been maintaining at about 5-7. (It's 30,000 gallons). Results from test kit run today: pH 7.3, Alk 140, free chlorine 5, combined chlorine 1, Cal 450, Cya 160 (1:2 dil with distilled water)

I know the Cya is very high. I did drain about 10-15% of the pool last week, but due to some unrelated plumbing issues I won't be able to drain more and refill for a few weeks. I'm finding it difficult to keep enough bleach on hand to keep the chlorine level up with such a high cya. Is it OK to use cal hypo to shock? Anything else I should be doing?

[PoolDoc]

The fact that you have FC=5, CC=1 suggests that you either have some goop yet to 'burn up' OR some algae that competing with you for control of the pool. Either could explain the high chlorine usage; with both you need to add a LARGE dose to either burn up what's left or kill all the algae. With CYA=160, you need to add at least enough to get you to 25 ppm. I don't see your pool gallons, but you'll need to add 5 gallons of plain 6% bleach per 10K gallons of water . . . and you should round up. So, if you have 25,000 gallons add 13 gallons of bleach, preferably in the evening.

Brush the pool the following AM, and then retest.

Read the "Best Guess" page for an explanation.

[CarlD]

Ben,
It's 30k.
If you can get 5 gallon carboys of 12.5% liquid chlorine it will be a lot easier to add to your pool. Just use 1 gallon of the LC where you were use 2 gallons of bleach. So you'd use 7 to 7.5 gallons of LC instead of 15 gallons of bleach--1.5 carboys rather than 15 bleach bottles.
Rest assured that LC is simply nothing more than double strength bleach. You just use about half as much for the same effect.

While they may look at you funny to see you loading 30 gallons of bleach in your cart, the pool stores will be HAPPY to help load 3 carboys for you...

Carl

[mdcbk]

Thanks! I haven't been able to find anyone selling carboys here. I can find 10% by the gallon at Warehouse pool. It costs slightly more than the 6% at the local discount store. I guess I can just give up my gym membership and get my workout loading and unloading bleach.

Why can't I use powdered shock, cal-hypo, to bring up the chlorine level?

[PoolDoc]

Why can't I use powdered shock, cal-hypo, to bring up the chlorine level?

Because, then you have to account for the effects of calcium and carbonates and hydroxides added by the cal hypo. It might be OK, but it might turn your pool in to a milky mess. Without test results from your K2006, we have no way of knowing.

[CarlD]

If your calcium level goes much over 400ppm, your risk of a milky pool increases. All dry chlorine combinations have drawbacks. Cal-hypo's is rising calcium. Di-Chlor's is lowering pH and raising CYA. Tri-Chlor's is REALLY lowering pH and raising CYA, too. Lithium is insanely expensive and we have not seen or heard of it working any better. Only bleach/LC have virtually no side effects.

Carl