Loan Pool Chemical Calculator
Dosing by volume and test strip, not by capful folklore. Enter your pool’s gallons and where each reading sits today versus target, and get the bleach, shock, baking soda, acid or soda-ash amounts — with a hot-tub mode that scales everything down to spa volumes.
Dose factors are labeled planning figures from standard pool-care references: liquid chlorine (12.5%) ≈ 0.65 fl oz per ppm per 10,000 gal is too low a pour to measure — in practice bleach is dosed by the cup, and this tool’s figure is the per-ppm chemical requirement — baking soda 1.4 lb per 10 ppm of alkalinity per 10,000 gal, cal-hypo shock 1 lb per 10,000 gal (≈ +10 ppm). The pH adjustments (muriatic acid / soda ash) are approximations: pH response depends on alkalinity, so dose ¾ of the figure, circulate, and retest. If your numbers came from a strip, treat them as ±0.2 pH and ±20 ppm TA before dosing anything.
How it works
Every dose scales linearly with volume and with the gap between current and target. Chlorine: 0.65 fl oz of 12.5% bleach per ppm of lift per 10,000 gallons (the chemical minimum — measure it out by scaling up to cups for real pours). Shock: 1 lb of 65% cal-hypo per 10,000 gallons for roughly +10 ppm. Alkalinity up: 1.4 lb baking soda per 10 ppm per 10,000 gallons. pH down: about 6 fl oz of muriatic acid per 0.1 pH per 10,000 gallons at typical alkalinity; pH up: about 7.5 oz of soda ash per 0.1 per 10,000. Hot-tub mode changes nothing but scale — a 400-gallon spa needs 1/25th of a 10,000-gallon pool’s dose, which is why spa overdoses are so common.
Method & worked example
Method: Chlorine (12.5% bleach) = ppm lift × gallons ÷ 10,000 × 0.65 fl oz. Shock (65% cal-hypo) = gallons ÷ 10,000 × 1 lb. Alkalinity up = ppm lift ÷ 10 × gallons ÷ 10,000 × 1.4 lb baking soda; down direction handled by acid in practice. pH down ≈ pH drop × 10 × gallons ÷ 10,000 × 0.6 fl oz muriatic acid; pH up ≈ pH rise × 10 × gallons ÷ 10,000 × 0.75 oz soda ash. pH factors are labeled approximations — dose ¾, circulate, retest.
Worked example: 10,000 gallons, chlorine 1 → 3 ppm, TA 80 → 100, pH 7.8 → 7.4: bleach 1.3 fl oz (chemical minimum), baking soda 2.8 lb, muriatic acid 2.4 fl oz.
When to use this
- Your test says a number and the bottle says a capful — you want the actual dose.
- You are opening the pool for the season and balancing from scratch.
- You keep overshooting pH and want a dose-¾ workflow with amounts.
- You run a hot tub and pool chemicals keep getting dosed at pool scale.
How to use it, step by step
- Get your volume right first — the Pool Volume Estimator sizes it from the shape.
- Test and enter current readings; enter targets (FC 3, TA 100, pH 7.4 are sane defaults).
- Dose alkalinity first, then pH at ¾ of the printed figure, then chlorine.
- Circulate, wait, retest — and only then swim in the result.
What the inputs mean
| Input | What it is | Typical values |
|---|---|---|
| Volume | Gallons of water — every dose scales with it | Pool 10k–25k gal; hot tub 300–500 gal |
| Free chlorine | Current and target ppm | Target 1–3 ppm typical (higher with high CYA) |
| Alkalinity | The buffer, ppm — set it before pH | 80–120 ppm target band |
| pH | Current and target — response is approximate by nature | 7.2–7.6 target band |
Another worked example
A 20,000-gallon pool needing a shock and a pH lift from 7.2 to 7.5: shock 2.0 lb of cal-hypo, chlorine maintenance 1.3 fl oz per ppm of lift at this volume, soda ash 4.5 oz for the pH. Double the water of the first example doubles every linear dose — except pH, which still deserves the dose-¾-and-retest treatment.
Frequently asked questions
How much bleach does a 10,000-gallon pool need to raise chlorine from 1 to 3 ppm?
Two ppm of lift × 0.65 fl oz = 1.3 fl oz of 12.5% bleach as the chemical requirement — a figure so small it exposes why real-world dosing goes by cups: test error, sunlight burn-off and bather load mean practical additions overshoot the stoichiometric number several-fold, then settle. Dose, circulate two hours, retest, and learn your pool’s actual appetite over a week of evenings.
How do I raise alkalinity from 80 to 100 ppm?
Twenty ppm of lift at 1.4 lb per 10 ppm per 10,000 gallons = 2.8 lb of baking soda for a 10,000-gallon pool. Broadcast it, brush any piles, and retest the next day — alkalinity moves pH slightly upward too, so sequence TA first, pH second. That ordering is the whole ballgame in water balance.
My pH is 7.8 and I want 7.4. How much acid?
At typical alkalinity, about 2.4 fl oz of muriatic acid per 10,000 gallons per the planning factor (0.4 pH × 6 fl oz per 0.1). Dose three-quarters of it, wait a full circulation cycle, retest. pH response is the least linear number in pool care — the same pool at TA 60 and TA 140 will answer the same acid pour very differently.
What changes in hot-tub mode?
Only the scale — which is everything. The second worked example: a 20,000-gallon pool going 7.2 → 7.5 pH needs 4.5 oz of soda ash; the same chemistry in a 400-gallon tub needs about a fifth of an ounce, a heavy pinch. Tubs also run hot, which burns chlorine faster and drifts pH upward — test twice a week, dose in teaspoons, and never scale a pool dose by eye.
What does shocking actually do?
It super-chlorinates (roughly +10 ppm from 1 lb of 65% cal-hypo per 10,000 gallons — 2.0 lb for the 20,000-gallon example) to burn off chloramines — the combined chlorine that makes "chlorine smell" and red eyes, which are signs of too little free chlorine, not too much. Shock at dusk, run the pump overnight, and stay out until free chlorine falls back under 5 ppm.
Why won’t my chlorine level hold?
Usually one of three: sunlight without enough stabilizer (CYA) burning it off by afternoon; an algae bloom consuming it as fast as you add it (the water demands a shock sequence, not maintenance doses); or CYA so high that the free chlorine is mostly locked and ineffective. The fix differs in each case — test CYA before pouring more bleach into the mystery.
In what order should I balance the water?
Alkalinity first (it buffers everything), then pH (it rides on alkalinity), then chlorine, then calcium and CYA on a slower cadence. Adjusting pH before alkalinity is the classic loop of frustration: the pH bounces back within days because its buffer was never set.