Daily High PH, High Alk, low chlorine

[bevcardinal]

FC 3.0
CC 0
PH 8.0
TA 150
CH 175
CYA 50
Temp 94

This summer has been a nightmare with our pool. We live in DFW area. Our pool is 18800 gal. in full sun all day, so water is 90 in the mornings and 94 in the evenings for the last two months. FC is usually at 4 each evening, but yesterday and today it was at 3 even though I added 16 c the previous evening. I've been using 8-16c of chlorine a day and the last few weeks 5-7c of muriatic acid daily. I have been unsuccessful in getting my TA down. I don't know what is going on. Before we cleaned our cartridge filters the PH was almost always at 7.6, but a few weeks ago we cleaned them (pressure is good after the filter clean) and now I can't keep the PH down. It's 8.0 by the next evening after dosing it with 5-7c of muriatic acid. Even with no water features running other than the pump 12 hrs. and vacuum 2hrs daily. We are on private well water, so I am always having a hard time getting our TA down, usually around 100-120, but this year is really bad. I feel like I am wasting money daily. We can't swim in a pool that is so hot it feels like soup, our tile is white with buildup, but the water is sparkling clear! Do I keep trying to get the PH and TA down? Why am I having to use so much chlorine daily??? Please help before we order a truck load of dirt and something gets buried! Thanks

 

[proavia]

In summer and using liquid chlorine, it would be better to have CYA at 60 to help reduce FC burnoff do to sun UV rays.

Dose FC to get to high side of target range. If the FC still falls to near minimum (or below), establish a higher target.

Let pH rise to 8.0, dose to lower to 7.2-7.4 and aerate to get pH back to 8.0 - rinse,repeat to help lower TA.
Shoot for a TA of 60-ish, which will slow rate of pH rise. With your highTA fill water, it will take constant monitoring.

With an 18,000 gallon pool, one gallon of 10% chlorine in the middle of summer is not unheard of.

 

[bevcardinal]

Thank for the help. I will add more chlorine tablets to raise my CYA a bit more.

"Let pH rise to 8.0, dose to lower to 7.2-7.4 and aerate to get pH back to 8.0 - rinse,repeat to help lower TA.
Shoot for a TA of 60-ish, which will slow rate of pH rise. With your highTA fill water, it will take constant monitoring."

How often should I check the ph rise? I've been checking it each evening. Should I check it more often, dose and aerate? How often should I check my TA? I've done this before and it took days for my TA to lower by even 10ppm. Should this be a really long process? I just want to be sure I am accomplishing something in the process. Thanks

 

[proavia]

How often should I check the ph rise?

Daily should be enough - unless you are seeing a quicker rise to 8.0-ish.
Maybe test a couple times a day to see how quickly the pH rises.
Be flexible and see what works best for your situation.

Once you get the TA to your goal, it's easier to keep it there than it was to lower it a large amount.

 

[SoDel]

As another way to skin the same cat (no offense to cats) — you can also lower the pH and let it rise naturally rather than trying to force it back up with aeratiion. Lower the pH as much as you are comfortable with in terms of CSI for your plaster. Test daily until you get a feel for how fast it tends to rise.

For example, my pool pH tends to rise somewhere between 0.1 to 0.2 per day (about 0.2 when TA is on the high end high and slowing as TA comes down over time). If I lower pH to 7.2, I know I can leave it alone for several days before needing to test, or dose with acid as needed. Once I get TA to about 50, pH rises about 0.1 per day or less and tends to stop rising completely at about 7.9. With a CH anywhere between 250 and 300, I can then basically leave it there for the rest of the season with a slightly negative CSI and not need to keep dosing acid (there’s enough rain here that adding water is rare).

In terms of a long process, yes, it can be a long process (like several weeks, perhaps more if your starting TA is very high) but if you only need to mess with it about once or maybe twice a week at first, it’s much less of a hassle. If you need to add a lot of high TA fill water to account for evaporation you’ll need to dose acid the entire season, but hopefully not more often than once a week. You’ll get a feel for it as you go.