Pool chemistry
Pool chemistry essentials
Clear water comes down to a handful of numbers: chlorine, pH, alkalinity, calcium hardness and stabilizer. Here they are in one place, with where each target comes from, the order to fix them in, and our tools and step-by-step articles for the jobs pool owners search for most.
The numbers to know
| Test | Target for a home pool | Source |
|---|---|---|
| Free chlorine | At least 1 ppm; at least 2 ppm with stabilizer. Typical range 1 to 4 ppm | CDC |
| pH | 7.0 to 7.8 (Taylor aims for 7.4 to 7.6) | CDC, Taylor |
| Total alkalinity | 80 to 120 ppm | Taylor |
| Calcium hardness | 200 to 400 ppm | Taylor |
| Cyanuric acid (stabilizer) | 30 to 50 ppm in pools (Taylor). Not in hot tubs, and with stabilizer the chlorine minimum is 2 ppm (CDC) | Taylor, CDC |
| LSI (water balance) | −0.30 to +0.30 | Taylor |
Sources: CDC home pool testing, CDC healthy swimming, Taylor Technologies (target ranges table), read November 3, 2026.
The CDC advises testing chlorine and pH at least twice a day for a home pool in use. Alkalinity, calcium hardness and stabilizer move slowly, so a weekly check is enough for most pools (our advice). Our weekly pool maintenance checklist puts it all in a routine.
Fix it in this order
- Total alkalinity first. It is the buffer: changing it moves pH too. How to lower alkalinity in a pool.
- Then pH. How to lower pH in a pool. Raising pH or alkalinity, and every other combination: pool pH and alkalinity.
- Calcium hardness last.
- Then sanitize. HTH's shock directions ask you to balance alkalinity and pH before shocking. How to shock a pool. Chlorine levels, types and problems: pool chlorine.
The first three steps are Taylor Technologies' order for balancing water. Change one thing at a time and retest before the next.
Need the amounts? Our pool chemical calculators work out how much chlorine, salt, baking soda, stabilizer or calcium chloride your pool needs for its volume.
Is the water balanced as a whole?
Each number can be in range and the water can still lean corrosive or scale-forming, because pH, temperature, calcium, alkalinity and dissolved solids work together. The pool LSI calculator combines them into one number and corrects your alkalinity for stabilizer and borate. In range means −0.30 to +0.30.
Handle pool chemicals safely
- Read and follow the label; wear gloves and eye protection (CDC).
- Never mix pool chemicals with each other; add them one at a time (HTH).
- Add chemicals to the water, never water to the chemicals, and never while people are in the pool (HTH).
- Store them cool, dry and out of direct sun (HTH); keep them secure and away from children and pets (CDC).
Pool chemistry tools and articles
- Pool LSI CalculatorBalanced, corrosive or scale-forming? One number from your test results.
- How to Lower pH in a PoolMuriatic acid or dry acid, how much, and how to stop pH rising again.
- How to Lower Alkalinity in a PoolThe acid and aeration method, step by step.
- How to Shock a PoolStep by step, and when you can swim again.
- Weekly Pool Maintenance ChecklistThe routine with the CDC chlorine and pH values.
Related topics
- How to Clear Cloudy Pool WaterCloudy water usually means filtration, chemistry, or circulation has slipped. Here is how to find which one and fix it fast.
- How to Fix Green Pool WaterGreen water means algae has taken hold. Here is how to shock, filter, and brush your way back to clear, and keep it from returning.
- What High Pool Filter Pressure MeansHigh pool filter pressure explained: how to find your clean baseline, what each pressure pattern points to, when cleaning fixes it, and what to check when it does not.
- Pool Filters