Is high TA an issue?

[eddman]

I have a 20x40 inground gunite/concrete pool. The pool is in a building with a clear roof. 41,00 gallons, sand filter. Use chlor with 3" tri-chlor tabs, supplement with bleach or cal-hypo 65?

I am typically getting TA readings of around 180 ppm with pH 7.2 - 7.5. CH readings are 200 - 220.

Is there an issue with TA at this level?

My biggest problem this year was killing off a major algae bloom and now trying to get FC/TC levels to stabilize.

Any comments on the TA or help with the FC/TC would be appreciated.

[madwil]

I don't think the TA is an issue immediately, but reaching a point along with CA that clouding could happen with a higher pH.
Nothing to worry about now, but if TA and CH increase over time, could become a problem.
The FC will stabilize if you completely killed the algae- did you maintain shock levels until no loss of FC overnight?

The clear rough may still shield out UV, so may change overall picture (indoor pools and outdoor pools are different!)

[CarlD]

TA and Calcium have little to do with algae. Actually, nothing. The risk of too high TA is of scaling, cloudy water (if CH is too high) and possibly pH that cycles up rather than down.
If you were in a vinyl pool I'd say do nothing but watch TA to make sure it doesn't pass 200. But with a concrete pool you should slowly start lowering it. Lower pH to between 7.0 and 7.2 (so you can continue to swim). This should lower TA somewhat. Then use aeration to raise pH back up. Splashing kids, a fountain, even pointing the return at the surface can do it. When pH rises to 7.5-7.7 or so, lower it again to the 7.0 to 7.2 range. TA should come down again. Aerate to raise pH and so, ratchet your TA down until it's in the 80-120 range.

Carl

[eddman]

I checked my levels again just a few hours ago. FC 0.5, TC 1, pH 7.2, CYA 30, TH 280, TA 150.

As for shock
question - yes, has been several days since treatment and no sign of reoccurrence.

I am planning to shock again tonight to try and drive FC up. Is about 9 gals og 6% about right?

[waterbear]

The high TA is only an issue if you have trouble maintaining the pH and have a high acid demand. High TA means a lot of carbonation in the water and one of the main causes of pH rise is outgassing of carbon dioxide from the water. If you are constantly battling high pH and need to add acid frequently then lower the TA. If your pH stays stable then don't worry about it. Also, the lower you put the pH the faster it rises because more of the bicarbonate is converted into carbonic acid (which is basically carbon dioxide dissolved in the water). The higher the amount of carbon dioxide in the water the faster it gasses off into the atmosphere. This lowers the amount of carbonic acid (which is the carbon dioxide dissolved in the water) (operative word here is acid). Less acid in the water means the pH has gone up!
(this explanation is purposefully oversimplified but still essentially correct)

[CarlD]

Evan's information is more precise than mine and he's right. IF pH is stable, don't mess with TA. It's it's always rising you'll want to lower T/A.

Meanwhile your chlorine level is very low and you need to boost it!

Carl

[madwil]

its important to shock the pool for a period of time- shocking is a process, not adding chlorine once.
When you have algae, you have to get to shock levels, AND maintain those levels for a period of time.
If you add chlorine once (which it sounds like you may have done), then let it drop back down, often all the algae isn't killed and it grows back; you maintain the shock level until all the algae is cleared, and any other material in pool (organics from dying algae, etc) is cleared by filter and/or oxidation
your TA shouldn't be an issue right now- but the cloudiness and FC stability issues are indicators of incipient algae blooms...