Why Should Sodium Bicarbonate Be Added Moderately Over Time To Reduce TA & Not All At Once
(Trinidad and Tobago)
I read in several places that when adjusting TA, it should be done with some degree of patience (1kg per 50,000 litres of water over 4 days), however, no one explains why this is so.
Why is it not recommended to make a 60ppm adjustment in one go?
Thanks for the question Brad
I want to clear up a part of your question. You probably meant for sodium bicarb to increase, not reduce the alkalinity. Muriatic acid is used to decrease TA and pH levels.
To do small adjustment, then test, makes perfect sense. This is normally when you have a very large adjustment to make. If you're TA is 130ppm and you want to get it down to 100, you can do it in one adjustment. It's not a huge difference.
You want to take it slowly when making a large adjustment. Say your alkalinity is 240ppm. Your target TA is 100ppm. That's a 140ppm jump. Many people are hesitant to pour 4 - 6 gallons of acid in the pool.
You don't want to over-shoot your goal. If you do, you'll need to make another adjustment to raise it.
It can also be bad for the pool surface. Pouring 5 gallons of acid into a pool can stain the liner.
I always tell people to make an adjustment, wait for one turnover of the water, then retest and make another adjustment if needed. By doing this in stages, you can see the results.
Many pool owners get impatient and want the results now. They may add acid, wait an hour, then test. They don't get a
reading so they add more acid, wait an hour and test again. They just doubled up on the acid. After a full turnover, normally about 8 - 10 hours, their readings are way too low.
Now they're angry that they overshot their target reading and need to make another adjustment that costs more time and money.
You can make a 60ppm adjustment, just be sure your measurements are correct. If you don't have the right measurement, you run the chance of not hitting your target reading.
I also tell people it's much easier to put chemicals in than take them out.
Last year during the YMCA shutdown, I couldn't be there to help with the pool. My supervisor had to raise the TA from 30ppm to 100ppm so he added 150 pounds (68 kg) of bicarb in one shot. It just had to get done "right now!"
He called me and said the TA is now 260ppm and the pH was way too high. It took 12 gallons of acid to get the TA to 100ppm and pH to 7.6ppm. Each gallon of acid is $8. He used more acid in 2 days than I use in 10 months.
In the end, having a little patience, making small chemical additions, and retesting, not only will get you to hit your target, but it saves time and money.
Hope this helps and have a wonderful day.
Comment By Brad
Thanks for your feedback. There was an error in my ques. I meant sodium bicar to increase TA and not reduce. You have answered my question.