Typical ph rise over time with SWG

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scuba
Pool Newbie
Pool Newbie
Posts: 8
Joined: Sun 05 Jun, 2011 16:04
My Pool: 30k gal free form diving, pebble tec, salt water
Location: Texas

Typical ph rise over time with SWG

Postby scuba » Fri 02 Sep, 2011 00:05

ph goes from 7.5 to 7.8 in about 2 weeks time. 2-3 quarts of acid brings it back to 7.5. Wanted to check if this is typical with a SWG or I need to manage the chemistry better? Thanks.

* FC: 5
* pH: 7.5
* TA: 90
* CH: 350
* CYA: 100
* Salt: 3200

* My pool: in ground, 30K Gal, PebbleTec
* Pool chemicals: Acid + acid + acid
* My pump & filter: Pentair 3HP
* Other info: 91F, normal, Texas summer heat, sun on pool, 6 hour pump run time, spa fountain and pool waterfall on when pump running.


chem geek
Pool Industry Leader
Pool Industry Leader
Posts: 2382
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Typical ph rise over time with SWG

Postby chem geek » Sun 04 Sep, 2011 00:58

That is typical, but in your case it isn't just the SWG but also the waterfall and fountain that are contributing to the pH rise due to aeration. If you lower your TA level to 70 ppm, you may find the rate of pH rise and the amount of acid that you need to add are lowered. You could even go a little lower in TA if you want, but you'll need to compensate with a higher Calcium Hardness (CH) level to protect the pool surface. Also, try and target 7.7 as the pH. As you can see from this chart the amount of carbon dioxide outgassing rises significantly at lower pH and higher TA (it actually rises with the square of the TA -- the chart just shows how over-carbonated pool water is with respect to air). If you have a way of turning off your waterfall and fountain (except when you really want to see it), then that should help as well.
scuba
Pool Newbie
Pool Newbie
Posts: 8
Joined: Sun 05 Jun, 2011 16:04
My Pool: 30k gal free form diving, pebble tec, salt water
Location: Texas

Typical ph rise over time with SWG

Postby scuba » Thu 08 Sep, 2011 17:44

Thanks for the info. I was off by 1 week, this time I checked more closely and it took 1 week to go from 7.5 to 7.8-8.0ish. I will bring the TA down to 60, shut off the pool waterfall and monitor for rise time in days. Spa fountain is designed to run as it makes the water spill from spa into pool but I can shut it off if needed.

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