Im having trouble getting the Ph and Alkalinity right in my Salt system pool.?

Question

I started out with Alkalinity at 280 and Ph at 7.4. The chem store sold me dry acid and after getting 40 lbs. of it in the pool, my Ph dropped to 6.4 with Alk at 120. I bought some Ph+ from Walmart and added 7lbs. Now my Alkalinity is back up to 180 with Ph at 6.8. I have a Vinyl pool with a salt system and approx 10,000 gal. What should I do? Someone told me to buy muratic acid from home depot and use it. Any help is much appreciated.

Answer 1

Muriatic acid is a lot easier to use to control both pH and TA, than granular acid. It just requires a little more care in storage and transport.

I suspect your issue is WHERE, in the pool you added the dry acid. To drop TA, you add it to the deep end, away from a pool return, so that it drops to the bottom. It will then drop your TA without touching your pH. To drop pH, you add it in FRONT of a pool return so that it immediately mixes in the water column and won't touch your TA. This is why using muriatic is better. It's already a liquid and mixes well if required.

Your salt system really has no bearing in this, since it's a common issue for any type of sanitizer. I suspect, jusdging by the pool volume here, this is an above ground pool? If so, and you have no deep end, dropping TA is done by turning off the pump, letting the currents settle for an hour, adding the acid ( start with 1.5 litres), give that an hour on the bottom and then turn you pump back on. Check you levels 24 hours later. If a further drop is required, well...you now know that 1.5 litres dropped it by X amount. Do some math to see what's required to get it to 120 or less and what X amount of acid dropped in the deep end effects Y amount of change. Every pool is a little different , there's no real magic number. Once you determine that number, write it down so that you have it for future issues.