If you ask most homeowners "what's your pool's alkalinity?" you'll get a shrug. Most folks test pH and chlorine. Maybe CYA once a year. Total alkalinity rarely makes the cut.
That's a mistake. Alkalinity is what keeps your pH stable. When alkalinity is right, pH stays where you put it for a week or more. When it's wrong, pH bounces around, you fight it constantly, and your water never quite feels right.
What alkalinity actually is
Total alkalinity (TA) is a measure of how much resistance to pH change your water has. Carbonates and bicarbonates dissolved in the water absorb acid and base before they can shift pH. So when alkalinity is high, pH is "stiff" — it takes a lot of acid or base to move it. When alkalinity is low, pH is "loose" — it swings every time something happens to the pool.
Think of it like the suspension on a truck. Stiff suspension absorbs bumps. No suspension and every bump rattles the cab. Pool pH works the same way.
Target ranges
Most chlorine pools: 80–120 ppm TA
Salt water pools: 60–80 ppm TA (slightly lower, because the higher TA fights the SWG's natural tendency to drive pH up)
Plaster pools: don't go below 80
Vinyl pools: a little more flexibility, 70–120 is fine
Why TA usually goes low — or stays low
In most Ellis County pools, TA drifts down over time, not up. Reasons:
Acidic rain (especially after a thunderstorm).
Adding muriatic acid (it lowers both pH and TA).
Trichlor tablets (slightly acidic).
Just the natural buffering action over months.
If your TA hasn't been measured in six months, it's probably lower than you think.
What goes wrong when TA is low
pH crashes after every rainstorm.
Adding small amounts of acid sends pH way too low.
Plaster surfaces start etching (the chalky white texture that shows up on old plaster).
Salt cells run rough and degrade faster.
Heaters and metal equipment corrode.
What goes wrong when TA is too high
pH gets stuck high — usually around 8.2 — and won't come down even with acid.
Calcium scale forms on plaster, tile, and inside the heater and salt cell.
Chlorine is less effective.
Water gets cloudy.
Raising TA with baking soda
Baking soda — sodium bicarbonate — is the right tool. Same baking soda you bake with. Pool stores sell it for 4× the price of the grocery store; if you have access to a Costco or Sam's Club in Waxahachie, you can buy a 13.5-lb bag for the price of a coffee.
To raise TA by 10 ppm in 10,000 gallons of water, add about 1.4 lbs of baking soda. The Total Alkalinity Calculator does the math for your specific pool.
Lowering TA — the harder direction
Lowering TA is slow and a little annoying. The standard method:
Add muriatic acid in a single dose, all in the deep end, with the pump off.
Let the acid sit and react with the carbonates for an hour without circulation.
Then turn the pump back on and aerate aggressively for several hours (waterfalls, fountains, upturned returns).
Retest the next day.
You'll often need to do this 2–4 times over a couple of weeks to bring TA from 180 down to 100. Don't try to do it all at once — your pH will crash and you'll have a different problem.
This is one of those "we can do this in a single visit" situations because we've done it a hundred times and we know how aggressive to be. If your TA has been over 150 for a while, call us before you start dosing.
How to actually add baking soda
Calculate the dose. Don't guess by the bag.
Dissolve in a bucket of pool water before adding. Granular sodium bicarbonate clouds the water badly if you dump it dry.
Pour into the deep end with the pump running.
Wait 6 hours, retest.
Don't add acid the same day.
When to call us
If you're testing TA monthly and it keeps drifting in the same direction, that's not a TA problem — that's a system telling you something else. Could be the sanitizer mix, could be source water hardness, could be a hidden leak refilling with soft water. Worth a chemistry diagnostic.
Run the Total Alkalinity Calculator or call Thomas directly at (214) 399-7347.
