4,000 gallon pool: how much of each chemical
A 4,000-gallon pool needs 4.1 fl oz of 12.5% liquid chlorine to raise free chlorine (FC) by 1 ppm.
Always follow your product’s label directions. Pool and spa chlorine, bromine, shock and algaecides are EPA-registered pesticides: use products labeled for pool or spa use, and don’t swim or soak until levels are within the limit on your product’s label. If this page and a label disagree, the label wins.
| Product | +1 ppm FC | +2 ppm FC | +5 ppm FC | +10 ppm FC |
|---|---|---|---|---|
| Pool liquid chlorine 12.5% | 4.1 fl oz121 mL | 8.2 fl oz242 mL | 20 fl oz606 mL | 41 fl oz1.21 L |
| Pool liquid chlorine 10% | 5.1 fl oz151 mL | 10 fl oz303 mL | 26 fl oz757 mL | 51 fl oz1.51 L |
| Household bleach 6% | 8.2 fl oz244 mL | 16 fl oz488 mL | 41 fl oz1.22 L | 82 fl oz2.44 L |
| Household bleach 8.25% | 5.8 fl oz172 mL | 12 fl oz343 mL | 29 fl oz858 mL | 58 fl oz1.72 L |
| Cal-hypo 65% | 0.8 oz23 g | 1.6 oz47 g | 4.1 oz116 g | 8.2 oz233 g |
| Dichlor 56% | 0.95 oz27 g | 1.9 oz54 g | 4.8 oz135 g | 9.5 oz270 g |
| Trichlor 90% | 0.6 oz17 g | 1.2 oz34 g | 3.0 oz84 g | 5.9 oz168 g |
Liquid chlorine percent is the trade percent on pool chlorine jugs; bleach percent is by weight. Cal-hypo adds calcium. Dichlor and trichlor add stabilizer (CYA). To shock, follow the directions on your product’s label.
| Product | Change | Amount |
|---|---|---|
| Baking soda | TA +10 ppm | 9.0 oz254 g |
| Muriatic acid 31.45% | TA −10 ppm | 10 fl oz303 mL |
| Dry acid 93.2% | TA −10 ppm | 13.7 oz389 g |
| Muriatic acid 31.45% | pH 7.8 → 7.5 (TA 100, CYA 40) | 3.8 fl oz113 mL |
| Dry acid 93.2% | pH 7.8 → 7.5 (TA 100, CYA 40) | 5.1 oz146 g |
| Soda ash | pH 7.2 → 7.5 (TA 80, CYA 30) | 5.9 oz168 g |
pH doses depend on your TA and CYA, so use the calculator for your numbers. Acid and pH-up amounts are rounded down.
| Product | Change | Amount |
|---|---|---|
| Stabilizer (CYA) | +10 ppm | 5.3 oz151 g |
| Stabilizer (CYA) | 0 → 40 ppm (new fill) | 1.35 lb606 g |
| Calcium chloride 77% | CH +10 ppm | 7.7 oz218 g |
| Calcium chloride 77% | CH +50 ppm (one step) | 2.4 lb1.09 kg |
| Pool salt | 0 → 3,200 ppm (new fill) | 107 lb48.45 kg · 3 × 40 lb bags |
| Pool salt | +500 ppm | 16.7 lb7.57 kg |
| Model | Capacity (manufacturer) |
|---|---|
| Intex Prism Frame 15ft x 48in | 4,440 gal |
| Intex Ultra XTR Frame 14ft x 48in | 3,861 gal |
| Intex Rectangular Ultra XTR Frame 18ft x 9ft x 52in | 4,545 gal |
| Bestway Steel Pro MAX 15ft x 42in (with LED light) | 3,955 gal |
On this page (9 sections)
With 10% chlorine, it takes 5.1 fl oz, and with 6% bleach, 8.2 fl oz. Four popular 14–18 ft frame pools hold between 3,861 and 4,545 gallons, so check your model before you trust a round number.
Quick answer: chlorine for a 4,000 gallon pool (depends on product)
To go from FC 1 to 4 ppm, add about 12 fl oz of 12.5% liquid chlorine, 15 fl oz of 10%, or 25 fl oz of 6% bleach. In dry form, that is about 2.5 oz of 65% cal-hypo or 1.8 oz of 90% trichlor. With stabilizer (cyanuric acid, CYA) at 40 ppm, keep FC in the 3–5 ppm range.
A full gallon of 12.5% chlorine would add about 31 ppm here, and a gallon of 10% about 25 ppm. Both are far more than a normal dose, so measure every pour.
Dose table: chlorine by product for +1/+2/+5/+10 ppm
The +5 ppm column is the one to bookmark for a rainy week or a pool party: 20 fl oz of 12.5%, 26 fl oz of 10%, or 41 fl oz of 6% bleach. The 8.25% "concentrated" bleach needs 5.8 fl oz per ppm, about 30% less than 6% bleach. Bleach percent on the label is by weight, while pool chlorine uses a trade percent, which is why 10% pool chlorine is not "twice as strong" as 6% bleach per fluid ounce. The chlorine guide explains the difference.
How much shock to add: the label, scaled to 4,000 gallons
Your shock product's label gives the dose, usually per 10,000 gallons. This pool is 0.4 times that size. If a liquid chlorine label says 1 gallon per 10,000 gallons, use about 51 fl oz here, a bit less than half the jug.
Cal-hypo sold in 1 lb bags adds about 19.5 ppm of chlorine per bag to 4,000 gallons and raises calcium by about 14 ppm. A label that says 1 lb per 10,000 gallons works out to about 6.4 oz, less than half a bag. Close the rest of the bag tightly and store it dry, away from acid and other chemicals. Don't swim until chlorine is back at or below the label's swim limit (often 4 ppm). More in how to shock a pool.
pH and alkalinity: acid and baking soda
With total alkalinity (TA) at 100 ppm and CYA at 40, lowering pH from 7.8 to 7.5 takes about 3.8 fl oz of 31.45% muriatic acid or 5.1 oz of dry acid. If pH starts at 8.0, the dose to reach 7.5 is about 5.3 fl oz, and the calculator splits it into two steps because it never lowers pH by more than 0.4 at once.
- Lower TA by 10 ppm: about 10 fl oz of muriatic acid.
- Raise TA by 10 ppm: about 9 oz of baking soda. See baking soda in a pool.
- Raise pH from 7.2 to 7.5 (TA 80, CYA 30): about 5.9 oz of soda ash.
Enter your own readings in the muriatic acid calculator for an exact number.
Stabilizer, calcium, and salt
- Stabilizer: 5.3 oz per 10 ppm; 1.35 lb from 0 to 40 ppm. The stabilizer calculator subtracts what you already have.
- Calcium chloride (77%): 7.7 oz per 10 ppm; 2.4 lb for one +50 ppm step.
- Salt: about 107 lb from 0 to 3,200 ppm. Two 40 lb bags reach only about 2,400 ppm. Most chlorine generators expect 2,700–3,400 ppm, so you need about 27 lb from a third bag. A later +500 ppm top-up is 16.7 lb. See the pool salt calculator.
Pools that hold about 4,000 gallons
| Model | Listed capacity | Geometry at 90% fill | Difference |
|---|---|---|---|
| Intex Ultra XTR Frame 14 ft × 48 in | 3,861 gal (fill not stated) | 4,146 gal | −6.9% |
| Bestway Steel Pro MAX 15 ft × 42 in | 3,955 gal | 4,164 gal | −5.0% |
| Intex Prism Frame 15 ft × 48 in | 4,440 gal | 4,759 gal | −6.7% |
| Intex Ultra XTR Frame 18 ft × 9 ft × 52 in | 4,545 gal | 4,726 gal | −3.8% |
For a 3 ppm top-up with 12.5% chlorine, the smallest of these needs 11.9 fl oz and the largest 14 fl oz. Using this 4,000-gallon sheet for the 15 × 48 Prism Frame underdoses by about 10%. That is within test-kit error for chlorine, but it's worth correcting in the calculator. Compare wall heights on the 15 ft round pool page.
Calculator preset to this volume
The calculator above is set to 4,000 gallons. Replace that number with your model's listed capacity and add your readings. The calculator then lists the steps in order, with wait times. Neighboring sheets: 3,000 gallons and 5,000 gallons.
Safety. Wear gloves and eye protection. Add acid to a bucket of pool water, never water to acid. Never mix acid and chlorine. Wait at least 30 minutes between them, with the pump on. Always follow the product label. Poison Control: 1-800-222-1222.
FAQ
How much chlorine do I put in a 4,000 gallon pool?
Per 1 ppm: 4.1 fl oz of 12.5% liquid chlorine, 5.1 fl oz of 10%, or 8.2 fl oz of 6% bleach. From FC 1 to 4, about 12 fl oz of 12.5%. For older jugs, use the liquid chlorine calculator.
How much shock for a 4,000 gallon pool?
Use the dose on your shock product's label, multiplied by 0.4 (4,000 ÷ 10,000). A cal-hypo label of 1 lb per 10,000 gallons becomes about 6.4 oz, and a liquid chlorine label of 1 gallon per 10,000 gallons becomes about 51 fl oz. Stay out of the water until chlorine returns to the label's swim limit.
How much muriatic acid for a 4,000 gallon pool?
About 3.8 fl oz of 31.45% acid for pH 7.8 to 7.5 at TA 100 and CYA 40, and about 10 fl oz to lower TA by 10 ppm. Retest 30 minutes after each dose.
Sources
- Intex, Ultra XTR Frame 14 ft × 48 in product page, read 2026-09-29: intexcorp.com
- Intex, Prism Frame 15 ft × 48 in product page, read 2026-09-29: intexcorp.com
- Intex, Rectangular Ultra XTR Frame 18 ft × 9 ft × 52 in product page, read 2026-09-29: intexcorp.com
- Bestway, Steel Pro MAX 15 ft × 42 in product page, read 2026-09-29: bestwayusa.com
- Hayward, AquaRite manual (salt range): PDF
- Formulas and reference checks: methodology