Balancing pH and Alkalinity?

[myra]

Hi - total pool newbie here!

We started looking after our pool ourselves a couple of weeks ago, having sacked the poolman who clearly wasn't doing his job.

The water looks very nice and clear, but I am having problems balancing pH and TA. The former always seems to be at around 7.8 - I add a pint of acid, it drops to 7.6, but next morning it's back at 7.8 or thereabouts.

TA has remained steady at 70. Yesterday I added 4 cups of baking soda to bring it up to 80, but this morning it's back at 70.

Today's numbers are:

FC = 2.0
TC = 2.0
TA = 70
pH= 7.8
CYA = 65

Ours is a 20,000 gallon AGP with Pebble Tec finish (concrete with ingrained pebbles). We are in California and the pool gets direct sunlight from sunrise till about 6 pm.

Many thanks for any suggestions.

 

[JasonLion]

Welcome to TFP!

PH tends to rise when you have a source of aeration, fountain, waterfall, SWG, water slide, etc. The frequent acid additions will lower the TA over time.

Letting PH settle around 7.8 isn't that bad. Or you could let the TA fall a little more, say to 60, and see if that helps.

Your FC level looks a little low. I would keep FC at 3 or even 4 with a SWG, and higher still with other sources of chlorine.

 

[myra]

Thanks, Jason!

So letting the TA drop further would not be detrimental to the chemistry of our pool?

Re. the FC: ours is a cartridge filter (STA-RITE System 3 Modular media Filter). The local pool store (yes, I know....) says between 1 and 1.5 is ideal. Needless to say, I don't buy that, but at the same time I do not want to add more chlorine then I have to. How important is it to get it to 3 or 4? (NB: My testing kit only goes to 3.0...) Would lowering the CYA by part-draining/refilling be a good idea?

Thanks again - I think this site is absolutely splendid!

 

[JasonLion]

The level of FC you need to maintain depends on the CYA level. With a lower CYA level you can have a lower FC level. If CYA was between 30 and 50 you could safely maintain a FC level of 2 or 3. However running a SWG with CYA below 60 requires a larger SWG, wears out the SWG cell more quickly, and can have some other minor negative side effects on your pool chemistry (such as increasing PH drift), compared to running with CYA between 60 and 80.