Total alkalinity target low?

[Scottamus]

Hi,

Does anyone know why in the pool math app, it shows that total alkalinity should be between 50-90? But everything else I’m seeing, including in the booklet for my new Taylor K-2006C test kit, says 80-120? Mine is 110 right now, and the app is telling me it’s too high…see screenshot. I can’t seem to change that target. Is that really the desired range? (I know my chlorine is high - I was taking care of a recent algae problem and getting more serious about testing).

 

[mknauss]

The old TA range of 80-120 is assuming you are using trichlor tablets to chlorinate with. When using a SWCG, it is best to let TA lower to 50 or slightly above, based on your CSI.

 

[Jimrahbe]

Scott,

Keeping my TA at 50 or 60, keeps my salt cell from producing calcium flakes..

Also makes my pH more stable..

With a CYA of 70, your FC is fine.. If you are running your FC at 3 ppm, it is why you have algae.

Thanks,

Jim R.

 

[mknauss]

I suggest you review Pool Care Basics

 

[mgtfp]

TA has two effects: The intended effect is a pH-buffer. A side effect is a constant pH-rise that gets more pronounced the higher TA is.

To increase TA, you add bicarb to setup a carbonate pH-buffer system. This means that the water is oversaturated with dissolved carbon dioxide that wants to gas out (like in an opened soda bottle). This outgassing raises pH in the process.

When chlorinating with Trichlor, which is highly acidic, you want both effects. The buffering to prevent pH from crashing, combined with enough carbon dioxide outgassing to create enough pH-rise to actively counteract the pH-pull from Trichlor. That's where the "old" TA recommendations come from, they are designed to keep a Trichlor chlorinated pool safe.

When using liquid chlorine or an SWG as chlorine source, which we highly recommend to prevent CYA from becoming unmanageably high from too much Trichlor, there is nothing pulling pH constantly down, and the pH rise due to carbon dioxide outgassing becomes best pronounced when using the"old" TA-range.

The solution is to maintain TA a bit lower, around 70. This still provides enough buffering when using non-acidic forms of chlorine, but reduces pH-rise due to carbon dioxide outgassing significantly.

 

[Scottamus]

Thanks all! Yeah, we’ve had the pool almost two years and never had algae. We were gone for 1.5 weeks at high pollen season and came back to a little bit on the bottom/side. Algae is gone now, pool is sparkling. I was just wondering about the TA. Thanks! I’ll try to keep it lower.

 

[JamesW]

What is your CSI?

 

[Scottamus]

Just saw this. It’s 0.20

 

[JamesW]

Turn on CSI Tracking and try to maintain about -0.3 to 0.0.

 

[Scottamus]

Working on it! It’s down to -0.04 now

 

[Scottamus]

Now it’s -0.26