New Pebbletec, pH, and Alkalinity

[tannybrown]

So we are new home and first time pool owners. The pool was resurfaced with Pebbletec, around February or March we believe, by the prior owner.

The pH is rising a bit on its own, which seems to be normal? The alkalinity is high, too. For details, pH was just a bit above 7.8 and alkalinity was at 170, so I added in a gallon of muriatic acid and brought it down to roughly 7.2. However, when I tested today, the Ph was back at 7.8 (it's been creeping up a bit daily as I've been testing), and alkalinity was somehow at 190 (?). I have not been aerating to bring pH back up because, well, it's rising on its own (due to the new plaster/Pebbletec, I believe).

I'd expected alkalinity to go down...I am new to testing so perhaps this is a case of user error. Here are today's numbers.

I have a few questions:

1) is there a target alkalinity I ought to shoot for or just let it be?
2) should I aerate to bring pH back up after adding acid?
3) with a new surface, should I aim for a particular pH or just keep knocking it down to 7.2 and see if it keeps creeping back up?

PH	7.8
FC	3.5
CC	0.5 (?)
TC	4
CH	325
TA	190
CYA	55

 

[Mr Bruce]

1) Keep adding acid. Eventually the TA will go down. You might find somewhere close to 50-60 is the best. I don't have Pebble-Tec but I have the slightly less expensive quartz mix, and to be honest, it's just now (3 years later) that my pool is "happy". And by happy I mean doesn't consume a gallon of acid a month. It likes TA of 50 and ph 7.5-7.8

2) You can try the Lowering TA method if you want it to go faster. Pool School - Lower Total Alkalinity

3) Don't shoot for 7.2, try 7.5 instead and wait until it's barely over 7.8 to add. You may find you need to add acid less often.

 

[elwood58]

I vote for knocking pH down to 7.2 and aerating pH up to 7.8, then repeat. You should be able to drop TA pretty dramatically. When TA comes down, Acid use will reduce.

 

[Mr Bruce]

Lowering TA may help, no question about it. It is not a magic bullet though, I just went back through my log that goes back to the beginning and I have always had lowish TA, always in the double digits. It would be a cheap and relatively easy thing to try, for sure, if you would like to. It's no guarantee.

 

[tannybrown]

I vote for knocking pH down to 7.2 and aerating pH up to 7.8, then repeat. You should be able to drop TA pretty dramatically. When TA comes down, Acid use will reduce.

Since the pH is rising on its own...is it necessary to aerate? I ask as I'm very likely just going to knock it back down to 7.2 again.

 

[Richard320]

One thing to consider: static electricity.

Sometimes the R-009 develops a static charge which makes the drops smaller and the TA reading then higher than reality. Just wipe the tip with a damp paper towel before testing TA to eliminate that possibility.

I wouldn't bother aerating. It'll take the same amount of acid to lower the TA no matter whether you do it over a month or an afternoon. Maybe when it gets below 100 you'll want to, but I suspect it raises plenty quick all by itself already.

 

[tannybrown]

Both are great points, thanks. I'll definitely try the damp towel to have more confidence in the reading.

And yeah, with the new pool surface I'm reading that this pool is going to raise its own pH for a while. Since I need to add acid, might as well let it lower the TA, too.

 

[Michael1]

One thing to consider: static electricity.

Sometimes the R-009 develops a static charge which makes the drops smaller and the TA reading then higher than reality. Just wipe the tip with a damp paper towel before testing TA to eliminate that possibility.

L always wondered why this was in the instructions. Thank you for your insight!