Enter your pool's gallons, how it is chlorinated and today's test readings. You get what to add, in the order to add it: alkalinity first, then pH, then stabilizer, each from the salt-cell maker's chart or the product's label.
To balance your pool
Add 4.5 lb of Alkalinity Up, then 12 oz of pH Up, then 1.7 lb of stabilizer to your 10,000 gallonsalkalinity 70 (80–120) · pH 7.0 (7.2–7.8) · stabilizer 20 (30–50)
Quick answer: Hayward and Pentair print the same ranges for a pool: pH 7.2 to 7.8, total alkalinity 80 to 120 ppm and stabilizer (cyanuric acid) 30 to 50 ppm outdoors. Fix the alkalinity first, then the pH, then the stabilizer. A sodium bicarbonate label: 1½ lb per 10,000 gallons raises alkalinity about 10 ppm. Hayward’s chart: 3.4 lb of stabilizer takes 10,000 gallons from 0 to 40 ppm.
How to use the pool water balance calculator
- Enter your pool’s gallons. The pool volume calculator works them out from the shape and depth.
- Pick where your chlorine comes from: a Hayward or a Pentair salt cell, or tablets and liquid. Each maker’s own stabilizer chart is used.
- Enter today’s readings for total alkalinity, pH and stabilizer from your test strips or kit. You get what to add, how much, in which order, and how long to wait before the next test.
Salt and chlorine are in the pool salt and chlorine calculator.
The rules, and where they come from
The ranges. Hayward’s AquaRite manual prints the Association of Pool and Spa Professionals’ levels: pH “7.2 to 7.8”, cyanuric acid “Outdoor pools – 30 to 50 ppm, Indoor pools – 0 ppm”, total alkalinity “80 to 120 ppm”, calcium hardness “200 to 400 ppm”. Pentair’s IntelliChlor guide gives the same pH, alkalinity and stabilizer, and “DO NOT USE CYANURIC ACID IN INDOOR POOLS”.
Alkalinity first. HTH’s pH Up label: “Before adjusting pH, test and adjust total alkalinity.” Leslie’s Alkalinity Up, 100% sodium bicarbonate: “1-1/2 lb per 10,000 gallons increases alkalinity level by approximately 10 ppm.” The calculator raises a low reading to 100 ppm, the middle of the range.
pH. The doses are HTH’s tables. pH Up (sodium carbonate), per 10,000 gallons: 8 oz from pH 7.2–6.8 at 50 ppm alkalinity, 12 oz at 100 ppm; from pH 6.4, 48 oz and 144 oz. pH Down (sodium bisulfate): 16 oz from pH 8.0–8.4, 24 oz above 8.4. Pentair names the other common pair: “USE MURIATIC ACID to lower pH and Soda Ash to raise pH.”
Stabilizer. Both salt-cell makers chart the pounds of cyanuric acid for 40 ppm: Hayward’s “needed for 40 ppm”, Pentair’s “to obtain 40 ppm”. Hayward’s chart is one sum, gallons × (40 − reading) × 8.345 ÷ 1,000,000, within 0.15 lb of every cell; Pentair’s is gallons × (40 − reading) × 8.125 ÷ 1,000,000. HTH’s stabilizer label rounds it to 1 lb per 10,000 gallons for each 10 ppm.
Too much stabilizer. Nothing removes it but fresh water. HTH: “If stabilizer levels are above 90 ppm, replace water.” Replacing a share of the water lowers the stabilizer by the same share.
Hayward’s chart: pounds of stabilizer for 40 ppm
| Stabilizer now | 8,000 gal | 10,000 gal | 12,000 gal | 16,000 gal | 20,000 gal | 24,000 gal |
|---|---|---|---|---|---|---|
| 0 ppm | 2.7 | 3.4 | 4.0 | 5.4 | 6.7 | 8.0 |
| 10 ppm | 2.0 | 2.5 | 3.0 | 4.0 | 5.0 | 6.0 |
| 20 ppm | 1.3 | 1.7 | 2.0 | 2.7 | 3.3 | 4.0 |
| 30 ppm | 0.7 | 0.8 | 1.0 | 1.4 | 1.7 | 2.0 |
From the AquaRite 900 manual’s page 6 chart, which runs to 40,000 gallons. Pentair’s Table 1 gives 3.25 lb for 10,000 gallons from 0.
HTH’s pH tables, per 10,000 gallons
| Reading | Product | Dose |
|---|---|---|
| pH 7.2–6.8, alkalinity 50 ppm | pH Up | 8 oz |
| pH 7.2–6.8, alkalinity 100 ppm | pH Up | 12 oz |
| pH 6.4, alkalinity 50 ppm | pH Up | 48 oz |
| pH 6.4, alkalinity 100 ppm | pH Up | 144 oz |
| pH 8.0–8.4 | pH Down | 16 oz |
| pH above 8.4 | pH Down | 24 oz |
HTH Pool Care pH Up and pH Down, from their own pages. Other brands differ in strength: read your product’s label.
Worked examples
Add 4.5 lb of Alkalinity Up, then 12 oz of pH Up, then 1.7 lb of stabilizer to your 10,000 gallons: a spring opening at alkalinity 70, pH 7.0 and stabilizer 20, on a Hayward cell. Retest the pH after the alkalinity: it may not need the pH Up.
Add 12 lb of Alkalinity Up to your 20,000 gallons: alkalinity 60 raised to 100 ppm, 1½ lb per 10,000 gallons for each 10 ppm.
Add 1 lb of pH Down, then 7 oz of stabilizer to your 10,000 gallons: HTH’s 16 oz for pH 8.0–8.4, and Hayward’s chart from 35 to 40 ppm.
Nothing to add to your 10,000 gallons; the stabilizer is high: at 80 ppm, replacing about half the water brings it back to 40.
Common mistakes
- Chasing the pH before the alkalinity. HTH: when alkalinity “drops below 80 ppm, pH won’t stay stable no matter how much pH Up you add.”
- Adding everything at once. Add one product, let the pump run, retest. HTH waits 12–24 hours after pH Up and 48 hours after pH Down or stabilizer.
- Too much stabilizer from tablets. Trichlor and dichlor add cyanuric acid every week. HTH: above 90 ppm, the only fix is fresh water.
- Stabilizer in an indoor pool. Hayward’s level for indoor pools is 0 ppm, and Pentair says do not use it indoors.
- Reading alkalinity without the stabilizer. Pentair: “Total Alkalinity – 1/3 Cyanuric Acid = Corrected Alkalinity”. At 100 ppm stabilizer, the correction is 33 ppm.
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Pool water balance questions
How do I use a pool alkalinity calculator?
Enter the gallons and today’s total alkalinity. Under 80 ppm, it gives the sodium bicarbonate to reach 100 ppm: 1½ lb per 10,000 gallons for each 10 ppm, from the Alkalinity Up label.
How much baking soda raises alkalinity in a pool?
Baking soda is sodium bicarbonate. Leslie’s Alkalinity Up, 100% sodium bicarbonate: 1½ lb per 10,000 gallons raises alkalinity about 10 ppm, so 4.5 lb takes 10,000 gallons from 70 to 100.
How much stabilizer do I add to my pool?
Enough to reach 40 ppm. Hayward’s chart: 3.4 lb for 10,000 gallons from 0, 1.7 lb from 20. Pentair’s: 3.25 lb from 0. HTH’s label: 1 lb per 10,000 gallons for each 10 ppm.
What does a pool stabilizer calculator work out?
The pounds of cyanuric acid to bring your gallons to the makers’ 40 ppm, or, if it is over 50, how much water to replace.
How do I lower the pH in my pool?
With an acid: sodium bisulfate (pH Down) or muriatic acid, as Pentair names. HTH’s pH Down: 16 oz per 10,000 gallons from pH 8.0–8.4, 24 oz above 8.4. Wait 48 hours before retesting.
What does a pool pH calculator tell me?
Whether the pH is inside 7.2–7.8 and, if not, the pH Up or pH Down dose for your gallons from HTH’s tables, after the alkalinity is right.
What is a pool chemical calculator?
A dose for your gallons and readings. This one does alkalinity, pH and stabilizer; the salt and chlorine calculator does salt, chlorine and shock.