pH drifting up, but why?

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C

cucamelsmd15

0
May 16, 2016
30
Belews Creek, NC
This is really the first full season of owning our house with a pool. I opened it to a swamp this year, did the SLAM, got the water clear and since then, Ive used 4-5 of the Trichlor pucks in the chlorine generator and a couple pound packs of shock for chlorine, but mainly to get some CYA in the water as well since I had none.

Over the past month that the pool has been open, post SLAM, Ive noticed a trend I cant put my finger on.

Chemistry wise:
TA: 80
CH: 200
CYA:50 (I keep this a little higher because the pool is on the N-NE side of the house and is 95% sun exposed during the day)
FC: 2-4 (Ive found adding about 1/2 gal of 10% bleach every other day is about right)

pH is whats bothering me. I use pH Down instead of MA, and twice within the past month, Ive had the pH slowly but steadily drift from 7.2-7.3 to 7.8+. Usually a dose of pH Down fixes the issue, but Im trying to understand why. The only major change Ive made lately is adding a pump timer that runs the pump 6 hours a day, usually from 10pm to 4am.

Thoughts?
 
Generally, there is a natural tendency for ALL pools to rise as they outgas. aeration and waterfalls speed that up but they still almost all rise.

Muriatic acid is a bit cleaner way to keep pH down (cheaper? I don't know) but that's your call.
 
Dosing about twice a month? You are a lucky one. Seriously, that is not bad at all.... But.....

7.2 - 7.3 is a little too low to try and maintain. The "bounce" from there to 7.5 is probably quick and then the move from 7.5 to 7.8 is probably slower. That is range you should be shooting for anyway. You could try and bring the TA down a bit to see if that helps. But what you are describing is not abnormal.
 
I would give you the things to consider this season:
- Watch your FC. Its low right now. Your target is 6 based on your CYA and should never be below 4. I add 1/2 gallon (2.5 ppm of FC) to my pool every evening as part of it's algae-free diet.
- pH will naturally rise as noted by others, but you might also benefit by lowering your TA just a little more; try 70, then 60 if needed.
- Remember that as it gets hotter, generally that means more water replenishment from evaporation. When you add new fill water, it usually has a higher TA (maybe even pH) so those together might rise as you add more water following evaporation.
 
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