How to balance pool water in 4 steps
Pool chemistry has a dirty secret: order matters. You can add the right chemicals in the wrong sequence and end up chasing your numbers all afternoon. Fix them in the right order and you'll get balanced water in one pass.
Here's the order, and why each step has to come before the next.
Test everything first
Before you add anything, test your water for at least free chlorine (FC), pH, total alkalinity (TA), and — if it's been a while — calcium hardness (CH) and cyanuric acid (CYA).
Write the numbers down or log them in an app. You need the full picture before making any decisions, because the steps interact — fixing alkalinity changes pH, and pH affects how well chlorine works.
Don't skip this. The most expensive pool chemistry mistake is adding chemicals based on what you think your water needs instead of what it actually needs.
Fix alkalinity first
Total alkalinity is the foundation. It acts as a buffer for pH — if alkalinity is wrong, your pH will be unstable no matter what you do to it. Fix TA first so that your pH adjustment in the next step actually sticks.
If TA is too low (below 80 ppm): Add sodium bicarbonate (baking soda). Use about 1.5 lbs per 10,000 gallons to raise TA by roughly 10 ppm. Dissolve it in a bucket first or broadcast it across the surface with the pump running.
If TA is too high (above 120 ppm): Add muriatic acid. Pour it slowly in front of a return jet with the pump running. This will also lower pH — that's expected and you'll address pH in the next step.
Wait time: Let the water circulate for at least 30 minutes before retesting. If you added a large amount, wait a full hour.
Why alkalinity comes before pH
Alkalinity and pH are linked — almost everything that changes one also changes the other. But alkalinity is the stabilizer. If you fix pH first without fixing alkalinity, your pH will drift right back within a day or two. Fix the foundation (TA), then fine-tune the result (pH).
Adjust pH
Now that alkalinity is in range, test your pH again (it may have shifted from the TA adjustment) and correct it.
If pH is too high (above 7.8): Add muriatic acid. For a 10,000-gallon pool, start with about 8 oz of 31.45% muriatic acid to lower pH by roughly 0.2 points. Go slowly — you can always add more.
If pH is too low (below 7.2): Add soda ash (sodium carbonate). About 6 oz per 10,000 gallons raises pH by roughly 0.2 points. Note that soda ash also raises alkalinity slightly — if your TA is already at the top of its range, use aeration instead (run a fountain, waterfall, or point a return jet at the surface). Aeration raises pH without raising alkalinity.
Wait time: 15–30 minutes of circulation, then retest.
Never mix chemicals
Never add acid and soda ash (or any two chemicals) at the same time. Add one, circulate, retest, then add the next. Mixing chemicals — even indirectly by adding them too close together — can cause dangerous reactions and waste product.
Adjust chlorine last
Chlorine goes last because its effectiveness depends on pH. At pH 7.2, about 65% of your free chlorine is in its active sanitizing form. At pH 7.8, only about 30% is active. Same chlorine, very different results.
By fixing pH first, you know exactly how effective your chlorine will be — so you can dose accurately instead of overcorrecting.
If FC is too low: Add liquid chlorine (sodium hypochlorite, 10–12.5%). For a 10,000-gallon pool, about 52 oz of 10% liquid chlorine raises FC by roughly 1 ppm. Add it in front of a return jet, ideally in the evening so the sun doesn't burn it off immediately.
If FC is too high: In most cases, just wait. Sunlight and normal usage will bring it down. If you need it down fast (for a pool party, for example), sodium thiosulfate is a chlorine neutralizer — but it's rarely necessary.
Wait time: Run the pump for at least one full turnover cycle (usually 6–8 hours) before retesting for a stable reading.
What about calcium hardness and CYA?
Calcium hardness and CYA (stabilizer) move slowly and don't interact with the alkalinity-pH-chlorine chain the way those three interact with each other. You can adjust them any time — but it's still smart to get the big three settled first.
- Calcium hardness: If it's low, add calcium chloride. If it's high, partially drain and refill. Neither affects your daily balancing routine.
- CYA: If it's low, add stabilizer. If it's high, partial drain and refill. CYA affects how much FC you need, but it doesn't change the order of operations.
When everything is off at once
Sometimes — especially at pool opening or after a big storm — every number is out of range. Don't panic. The same order still applies:
- Test everything and write it down
- Fix alkalinity
- Retest, then fix pH
- Retest, then fix chlorine
- The next day, check calcium and CYA
You may need to go through the cycle twice if things were way off. That's normal. Each pass gets you closer, and by the second round you're usually just fine-tuning.
The common mistake
The most common balancing mistake is dumping everything in at once — acid, chlorine, and soda ash within an hour. The chemicals interact with each other instead of the water, you waste product, and you end up with numbers that are harder to fix than when you started.
One chemical at a time. Circulate. Retest. Then the next. It feels slower, but you'll actually finish faster because you're not undoing your own work.
Let the app handle the math
PoolChem Tracker tells you what to add, how much, and in what order — based on your pool size and current readings. Log your test results and get step-by-step dosing recommendations instantly.
