Add chemicals safely: one at a time, with the pump running, waiting for each to circulate before testing and adding the next. Never mix concentrated chemicals together, always add chemical to water rather than water to chemical, and follow the dose printed on your product — concentrations vary between brands, and the figures here are typical planning values.
Quick answer: pool doses are specified per 10,000 gallons, and everything scales from your volume. To raise free chlorine 1 ppm takes about 10.7 fl oz of 12.5% liquid chlorine per 10,000 gal. Don't know your volume? Start with the pool volume calculator.
Target ranges
| Parameter | Ideal range | Why it matters |
|---|---|---|
| Free chlorine | 1–3 ppm | Sanitiser; too low and algae grows, too high stings eyes |
| pH | 7.4–7.6 | Comfort and chlorine effectiveness; drives corrosion or scale |
| Total alkalinity | 80–120 ppm | Buffers pH against sudden swings |
| Calcium hardness | 200–400 ppm | Too low corrodes surfaces, too high scales |
| Cyanuric acid (stabiliser) | 30–50 ppm | Protects chlorine from UV; too high weakens it |
Adjust in this order: alkalinity first (it stabilises pH), then pH, then calcium and stabiliser, and chlorine last. Alkalinity is the buffer — get it right and pH becomes far easier to hold steady.
The dose rates behind the calculator
All figures per 10,000 gallons; the calculator scales them to your pool:
| Goal | Product | Dose per 10,000 gal |
|---|---|---|
| Raise free chlorine 1 ppm | Liquid chlorine (12.5%) | 10.7 fl oz |
| Raise free chlorine 1 ppm | Cal-hypo (73%) | 2.0 oz weight |
| Raise free chlorine 1 ppm | Dichlor (56%) | 2.4 oz weight |
| Raise pH 0.2 | Soda ash | 6 oz weight |
| Lower pH 0.2 | Muriatic acid (31%) | 12 fl oz |
| Lower pH 0.2 | Dry acid (sodium bisulfate) | 12 oz weight |
| Raise alkalinity 10 ppm | Baking soda | 1.5 lb |
| Raise calcium 10 ppm | Calcium chloride | 1.25 lb |
| Raise stabiliser 10 ppm | Cyanuric acid | 13 oz weight |
Lowering alkalinity, calcium or stabiliser is harder — there is no additive that removes them, so it usually means partially draining and refilling with fresh water. This is why the guidance is always to raise these gently and retest, rather than overshoot.
Why the volume comes first
Every dose on this page is a rate per unit of water. That makes your pool volume the multiplier on everything you add, all season long. An error there is not a one-off — it repeats on every single dose.
Suppose your pool actually holds 20,000 gallons but you believe it holds 25,000. Every chlorine addition lands 20% weak, so the water is persistently under-sanitised and you never quite understand why. Believe it holds 16,000 and you overdose by 25% each time, wasting product, risking a bleached liner, and sometimes pushing chlorine high enough that the pool is not safe to swim in.
Measure the pool once, properly, and write the figure on the equipment pad. The pool volume calculator handles rectangular, round, oval and kidney shapes with sloped floors.
Common mistakes & pro tips
- Wrong volume. The multiplier on everything. Get it right first.
- Dosing all at once. Add in stages, circulate, retest. Overshooting is hard to undo.
- Adjusting pH before alkalinity. Alkalinity buffers pH, so fix it first or pH won't hold.
- Ignoring stabiliser. Too much cyanuric acid locks up chlorine, and the only fix is dilution.
- Pro tip — dose to the middle of the range. Aiming for the centre of each target band leaves room to drift in either direction before the next test.
- Pro tip — test in the evening. Sun burns off free chlorine through the day, so a morning reading flatters you. Test and dose when the sun is off the water.
Frequently asked questions
How much chlorine do I add to my pool?
To raise free chlorine by 1 ppm you need about 10.7 fluid ounces of 12.5% liquid chlorine per 10,000 gallons, or about 2 ounces by weight of cal-hypo. The exact amount scales with your pool volume, so an accurate gallon figure is the first thing to get right.
How do I raise pool pH?
Soda ash (sodium carbonate) raises pH. A rough guide is about 6 ounces per 10,000 gallons to lift pH by 0.2, though the exact amount depends on total alkalinity, which buffers pH changes. Add in stages and retest rather than dosing the whole amount at once.
How do I lower pool pH?
Muriatic acid or dry acid (sodium bisulfate) lowers pH. Roughly 12 fluid ounces of 31% muriatic acid per 10,000 gallons lowers pH by about 0.2. Acid also lowers total alkalinity, so the two are usually adjusted together.
What order should I add pool chemicals?
Adjust total alkalinity first, because it stabilises pH; then pH; then calcium hardness and stabiliser; and chlorine last. Add one chemical at a time with the pump running, wait for it to circulate, and retest before adding the next. Never mix concentrated chemicals together.
Why does pool volume matter so much for dosing?
Every dose is specified per unit of water, so an error in your volume becomes the same percentage error in every chemical you add all season. Overestimating a 20,000 gallon pool as 25,000 means you underdose by 20% every time; underestimating means you overdose, which wastes money and can damage the pool or make the water unsafe.