The Beginner’s Guide to Pool Chemistry: pH, Alkalinity, Chlorine & More

Clear, comfortable, safe water isn’t guesswork—it’s a small set of numbers kept in range. This beginner’s guide from Pool Life explains what each number means, how they interact, and the exact order to balance them so your pool stays sparkling with less effort (and fewer chemicals).

Pool Chemistry – The five essentials (and why they matter)

1. pH (acidity/alkalinity of the water)
   • Target: 7.2–7.6
   • Why: Comfort for eyes/skin, and how powerful chlorine is. At higher pH, chlorine works more slowly.
2. Total Alkalinity (TA: your pH “buffer”)
   • Target: 80–120 ppm (fibreglass often 60–100 ppm)
   • Why: Stabilises pH. Too low = pH swings. Too high = pH constantly drifts upward.
3. Free Chlorine (FC: your sanitiser)
   • Target: 1–3 ppm (salt pools often 2–4 ppm)
   • Why: Kills germs/algae and oxidises contaminants.
4. Stabiliser / Cyanuric Acid (CYA: chlorine’s “sunscreen”)
   • Target: 30–50 ppm
   • Why: Protects chlorine from sunlight; too high makes chlorine sluggish.
5. Calcium Hardness (CH)
   • Target: 200–400 ppm (fibreglass 175–250 ppm)
   • Why: Prevents etching (too low) and scale (too high), protecting surfaces and heaters.

For salt systems, also watch the salt level per your chlorinator (commonly 3,000–4,500 ppm).

Test smarter, not harder.

• Summer / heavy use: Check pH & FC every 2–3 days, full test weekly.
• Milder months: Weekly pH & FC, full test fortnightly.
• After storms/parties/heatwaves: Test straight away, then again the next day.
• Sampling tip: Run the pump 30 minutes, dip elbow-deep, away from returns/skimmers, and test immediately.

Best tools: A quality drop-test kit or photometer (most accurate), plus a logbook/app to track results and doses.

Balance in this order (Pool Life method)

1. Total Alkalinity (TA)
   • Raise with sodium bicarbonate (buffer).
   • Lower the acid in stages while aerating (aim returns up, use water features).
2. pH
   • Lower with pool acid (hydrochloric/muriatic).
   • Raise with soda ash.
   • Make small changes, circulate for 2–3 hours, then retest.
3. Calcium Hardness (CH)
   • Raise with calcium chloride.
   • If too high, dilution is the practical fix (and keep pH/TA on the lower end to minimise scale).
4. Stabiliser (CYA)
   • Add conditioner slowly; it dissolves over days.
   • Avoid overshooting—high CYA is hard to reduce (requires dilution).
   • Remember: Trichlor/dichlor tablets add CYA each time you use them.
5. Free Chlorine (FC)
   • Dose liquid chlorine to target; if FC is near zero or algae is suspected, shock to a higher level matched to your CYA.
   • Salt pools: Use liquid chlorine for big corrections; let the chlorinator maintain day-to-day.

How the pieces interact (the simple science)

• pH ↔ Chlorine power: Lower pH = stronger chlorine (within safe range).
• TA ↔ pH stability: TA acts like a shock absorber; fix TA before chasing pH.
• CYA ↔ Chlorine demand: Sunlight destroys unprotected chlorine; CYA shields it—but too much CYA slows chlorine’s kill rate.
• CH + pH + TA ↔ Scale/etch: High CH with high pH/TA + warm water = scale; low CH with low pH can etch plaster.

Dosing tips to avoid yo-yo chemistry

• Know your pool volume (in litres) so dose amounts are accurate.
• Circulate first, add chemicals in the deep end, and keep the pump running.
• Split significant adjustments into two or three smaller doses with retests between.
• Keep acid and chlorine separate (don’t add in the same spot/time).
• Safety: Gloves and eye protection; add acid to water, never water to acid.

Special notes for saltwater (SWG) pools

• Keep salt in the manufacturer’s window; clean the cell when scaled (avoid frequent strong-acid washes).
• In hot, sunny weather, increase pump run time or SWG output to hold FC.
• Use liquid chlorine for recovery shocks—generators are for maintaining, not rapid spikes.

Quick diagnostics

• Cloudy water: Check filter cleanliness/run time, set pH ~7.4, ensure FC in range; consider a clarifier if needed.
• Green tinge/algae: pH to ~7.2, shock to a killing FC level for your CYA, brush thoroughly, filter 24/7 until clear.
• Strong “chlorine smell”/stinging eyes: Usually chloramines (combined chlorine). Shock and improve circulation; keep pH 7.2–7.6.
• Scaling/rough feel: Bring pH/TA to the lower end; consider a scale inhibitor; check CH.
• pH keeps climbing: TA likely high or lots of aeration (spillways/spa jets). Lower TA gradually.

Optional helpers (use wisely)

• Clarifiers: Clump fine particles so the filter can grab them—great after storms.
• Flocculants: For rapid clearing—settle, then vacuum to waste (don’t run through cartridges/DE).
• Phosphate removers: Useful if you have recurring algae and heavy debris loads.
• Borates (30–50 ppm): Can stabilise pH and add sparkle—seek advice before adding.

What can Pool Life do for you?

• On-site testing & balancing with precise results and personalised recommendations.
• System tune-ups: Pump run-time programming, chlorinator setup, and filter optimisation.
• Green-to-clean recoveries and seasonal service plans to keep numbers steady year-round.