Long Hot Summer and Pool

[DallasVal]

We began the season with a quartz resurfacing of our 10 yr. old gunite pool. Late spring rains and weepers at light fixtures delayed the process, but the job was finally completed around June 10. So we are about 2.5 months into the curing process. Here in Dallas, we are also experiencing something like our 58th day of triple digit days - many reaching 103 - 107. Lows are in the mid 80s. Oh yeah - I forgot to mention drought conditions, which mean lots of sunshine.

Your site has been my guide since re-filling the pool, regardless of what the pool store guys tell me. However, maintaining the appropriate balance with the unrelenting sun has become an increasing challenge. Plus, the plaster is curing. I'm a bit worried about the rapid rise in hardness and CYA (understand the contributing factors -curing process, local hard water and trichlor), in spite of adding at least an inch of fresh water every day. I'm also not sure how hard I should fight my pH. Guess I'm looking for feedback, more than anything, as I want this surface to last a bit longer than the original plain, white plaster and I want it to be safe. Facts (using Taylor test kit):

FC - 4
TC - 4
pH- 7.8 (no matter how I try to lower it with muriatic acid, that's where it seems to want to settle)
TA - 100
CH - 470
CYA - 100 (added CYA on filling to reach 30; using trichlor tabs for maintenace, bleach to shock; added cal hypo to shock before leaving for 4 day trip last week)
Water Temp - 92 average, usually hits 94 late in day
Only water feature is a standard fountain in the spa
13,000 gal gunite pool with quartz plaster finish

TA has pretty much settled at 90 - 100. pH bounce is less severe than the first few weeks - hits high of 8.2 periodically, but stays at 7.8, if allowed, for a few days straight. Had been trying to keep it at 7.6, but it doesn't want to stay there. I also added 20 Mule Team Borax around week 2.

I can't change the temps. I can't change the hardness factor. Am now headed to grocery for more Clorox to raise chlorine. Note that pool is generally used by two adults - no kids, little tanning oil.

Do you recommend any adjustments? TIA for any input.

[PoolDoc]

Hi Dallas;

You have to keep your pH down, no matter how much muriatic it takes. I can't estimate what the results of your plaster curing will be, but I can tell you you'll have to use as much acid as it takes. So long as you are not adding soda ash or sodium bicarbonate . . . there's not much else you can do. Hard water -- like your fill water -- is often also high in carbonate alkalinity, so that may also be a source of your pH rise. But, when water evaporates, you have to replace it. So it all comes back to, "Add enough acid to get the job done, however much that it!"

High water temperatures definitely seem to make things harder and there's not much you can do about that, either.

But, you DO want to increase your chlorine levels, or you WILL likely have algae problems. Check the Best Guess chart (links in my sig!) for correct chlorine levels with a CYA = 100.

[DallasVal]

Thanks for the quick response, Ben. I do understand I need to get the chlorine levels up with the CYA so high and have been referencing the Best Guess chart. Hence, the trip for bleach. Should be up to par again by tomorrow morning. At least the water has been solidly crystal clear for the last 2 months, with no algae, even in this heat. But regarding the pH.....I get that I have to keep it down. My question - is 7.8 OK, or do I need to keep it at 7.6, regardless of constant acid demand? I do realize my LSI is high right now, with scale a threat, which is one of the last things I want. It's just that the pool seems to want to stay at 7.8.

The site is such a help. Thanks for keeping us straight!

[PoolDoc]

If it's actually 7.8, and not "at the top of my test kit scale which is 7.8" . . . you'd be OK. The problem is, if it's at the top of your kit's scale, then 7.8 REALLY means 7.8 or higher, not 7.8 actually.

However, given the high CH, you probably need to hold a pH of 7.2 for awhile in order to lower your TA, which drops when you hold your pH low AND aerate. (Lower pH turns some of the TA into carbon dioxide, when then leaves the pool slowly without aeration or more rapidly with it.)

[DallasVal]

It is actually 7.8 - test kit goes to 8.2 and the colors are noticeably different. The spa has a fountain and water circulation is shared (common pump), so it aerates. I'll take your advice and drop the pH for a while to see what happens. As I read your response, I also need to keep TA lower (which will happen as a result of pH going down with muriatic acid added). It had been hovering in the 80 - 90 range in the beginning. Back then, when I took the water to the pool store to have it tested as verification of my tests, the guy was adamant that I needed to get TA up to 100 - 125.

Thanks again.