TA test, pH and FC at shock levels

rlsnights

Well-known member
Sep 9, 2008
79
current numbers:

FC 21
CC 0
pH unk
TA 110
CH 270
CYA 50
M-O-U-S-E Th-th-th that's all folks :wave:

My question:

Can I use changes in TA as an indicator of pH changes since the pH test isn't valid at these FC levels?

Background:

I have been shocking our pool for five days to treat (again) black algae. I know why this is a recurrent problem with our pool but there's not a lot I can do since the issue is my inability to get out and test/treat the pool daily due to family and personal illness requiring overnight travel, etc. and it's BA I'm dealing with in a plaster pool.

When I'm home I check the pool first thing and adjust but sometimes the FC has dropped to zero if I've been unable to tend it for 2 or 3 days in a row. This is despite having a floater in the pool (I have decided to add a 2nd floater when I'm gone and see if this helps keep the FC up during the day) and adding extra chlorine before I leave - provided I have enough notice.

A drop to zero almost always signals a new BA bloom.

With the current bloom we are loosing huge amounts of FC despite visible improvement in the BA. We don't get big patches of BA just the small "dots" in problem areas. Anyway, our overnight loss has dropped from 16 ppm to 7 ppm last night (4th day of shocking) so I know we are making progress.

During the day we were loosing an additional 12 - 16 ppm with daytime temps in the low 80's. Daytime loss yesterday was 10 ppm but the temp was 106 so I'm not sure how much of that was BA and how much the heat. I was pleased that the loss was that low and think we are definitely getting ahead of the curve now. We are brushing between 1 - 3 times a day, usually 2 times a day.

Historically we have had issues with rising pH and difficulty getting our TA down. In the past it's usually been 110-120. I had finally gotten the TA down to 80 ppm by adding acid several times. The pH had been stable at 7.5 for 3 days when I had to take a 3 day break in caring for the pool.

Anyway, these numbers were still good when I began shocking the pool.

Then 2 days ago the TA rose to 90. yesterday morning it was 110. Last night it was 120.

So I am thinking that I need to add acid since the pH is probably rising and driving the TA up.

I had a couple odd color changes in my TA tests (instead of pink it was turning light orange) so I increased my R-007 from 2 drops to 3 or 4 and this gave me the typical TA test changes of green to fruit punch pink. Hopefully this isn't affecting my TA test results.
 

Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
23,626
SouthWest Alabama
It sounds like it's time to consider a chlorine feed system of some type. Letting your FC go to zero for any length of time, especially since you already have a problem, is going to create issues.

Here are a few choices in no particular order.
  • Salt Water Chlorine Generator.[/*:m:ddw7p4f1]
  • Liquidator.[/*:m:ddw7p4f1]
  • Peristaltic Feed Pump & Tank.[/*:m:ddw7p4f1]

I'd strongly suggest you consider one of the above.
 

rlsnights

Well-known member
Sep 9, 2008
79
I didn't know there was such a thing. I will check it out ASAP.

What do you think about using TA as a marker for pH levels?
 

Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
23,626
SouthWest Alabama
I don't think you can use TA as a pH indicator. If you feel you have to check it, just let your FC come down to about 10 to 15 and test it then.