New In-Ground Plaster Pool Chemistry-SWG and PH/TA Drift

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HouTexYankee

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Jun 14, 2013
7
Our new pool was built over the winter and this is my first pool. As I posted in my intro, I've relied heavily on the info on these boards to get my chems started in the right direction. Things are going great for the most part; however the only minor issue I'm experiencing is my PH and TA are tending to creep up. I suspect this may be something I'm just going to have to live with due the combination of pool features and the nature of the fill water where I live. Our pool includes an 8 foot round spa that has a large spill into the pool. Combined with the SWG, and occasional use of the sprays on our raised wall the result is a lot of aeration. Fill water is off my scale at 8+, TA starts at about 120 PPM. Being an aquarist, I suspect like in an aquarium, our pool water is naturally going to want to return to its baseline, and I will continuously need to add acid to control the rise. I just wanted to be sure I'm not missing something due to inexperience. I've kept a journal of test results since fill; Chems as follows:

Start-up (March 29): PH 8+; TA 120 PPM; CA 120

Current: FCL 6.5; CC 0 to .2; PH 7.8; TA 80; CA 340; CYA 70; Temp about 93'; pump run time 1200 through 2000; SWG set to 65%

About every other day or two I add about 10 Oz to 20 Oz MA to control the PH, which tends to rise to 8+ rather quickly. I've tried to patiently lower TA by dropping PH and aerating. Lowest its gotten was 75.

Any input is appreciated.
 
You've got two things fighting you. 1) you have a new pool which is going to cause the pH to rise for a while and 2) you have a swg, which also causes the pH to rise. Just keep adjusting the pH to the low 7's and eventually the TA will come down and the pH will somewhat stabilize.
 
Because of your high TA fill water, you are an excellent candidate for getting an automatic acid feed system. High TA fill water means the PH will pretty much always be climbing. There are things you can do to slow down the rate at which it climbs, but as fill water constantly raises the TA, you can never stop the PH increase completely.
 
Automating the acid feed sounds like our solution, especially since at some point, I'd like to be able to go on vacation. :-D I'm thinking to give it a year or so to see if it will stabilize somewhat as the plaster gets older. However, I think the writing is on the wall due to the high TA fill water.
I don't mind manually adding the acid, and I actually enjoy working around the pool.

Thanks again
 
Just a note that if you close your pool for winter you'll really want a way to handle that TA and pH drift, or you're in danger of opening up with scale. We re-plastered a few years ago and even though I've had sparkly water every summer thanks to this site it's the winter closing that did me in. We are looking at draining and acid wash--the kids get sore toes if they stay in for hours because of the rough floor. Then we'll keep a submersible pump in for the winter and try and keep up with it until the water freezes. (I'm in PA)

Sorry if this is too off topic, just wanted you to know what I wish I did.
 
I have a SWG and a spillover spa and my pool is 2.5 years old and I'm still adding about a quart of MA each week. The TA of my fill water is 220 so it's hard to get my TA below 70.

As for vacation, I just add a little more acid than usual just before I leave and don't worry about it. If you are gone for a month it might be a problem, but a few days of high pH hasn't harmed my pool.
 
I am in the exact same boat as you. My Ph rises by .2 every day due to new plaster, SWCG, and aeration. I agree with HouTex. Drop it to 7 before you leave for vacation. A couple of days with high PH is not going to harm anything. If you are really concerned, maybe you could get a friend to dose the acid while you are away.
 
Not off topic at all Maria. Thanks for the info. Fortunately, the weather will likely permit me to run this year round, so I'm hoping I won't deal with closing issues.

Scale is the primary reason for my concern. My thinking has been PH a bit on the higher side would be better than aggressive water in that it wouldn't damage the plaster. I dont mind getting after it with the pumice stone. However, scale to the degree it affects my plumbing/mechanicals is a concern.

Thanks again guys.
 
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