MA, pH, TA, and salt

[dhosbein]

I’ve read some discussions about the relationship between MA, pH, TA, and salt, but none seem to address my concerns:


Can MA, added on a regular basis (i.e., every few days, weekly), raise pool salt levels enough (i.e., >= 4200ppm) to make my SWCG stop working?

• Contrary to a previously posted comment that, “…every gallon of muriatic acid (31.45%) adds ~36ppm of chloride ions to 10,000 gallons of pool water,” my salt levels appear to be trending upward at a faster rate than that statement suggests. Here is a log on my 3 month old pool:
• I am now skeptical about adding more MA. How can I maintain acceptable pH, TA, and salt levels without partially draining and refilling my pool every few weeks?

Here’s a little background:

• My 4.5k gallon salt water pool is 3 months old.
• All chemical calculators (PoolMath, etc.) recommend adding 6-12 ounces of MA to lower pH and TA to target levels. Repeated attempts beginning 7/1/22 have failed to lower pH and TA (possible bad batch of MA?). Note: I fired my pool maintenance company on 7/1/22 and am now doing this myself.
• I live in Arizona so we don’t get a lot of rain.
• Water is expensive and in short supply.
• All salt readings in the above log are from the SWCG and are within +/- 100ppm of measurements using the Taylor K-1766 test kit.

 

[needsajet]

I suspect the rising TA is similar to your calcium rising, being coming in from fill water. I would just add enough MA to keep pH below 8.0 (i.e. 7.8 or less), and not be concerned with acid adding salt. It would surprise me if your SWCG has any issues with the salt level.

Lowering TA is just a technique to make acid additions less frequent. The same total amount of acid will be needed to offset the incoming TA.

As you learned, don't add baking soda unless you actually crash the TA below 50, which I think is unlikely.

You're experiencing the challenges of a small body of water, and doing fine, imo. I'd be careful on the FC which looks a bit low.