500 gallon pool: chemical doses for small filtered pools
In a 500-gallon pool, 0.6 fl oz (just under 4 teaspoons) of 10% liquid chlorine raises free chlorine 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% | 0.5 fl oz15 mL | 1.0 fl oz30 mL | 2.6 fl oz76 mL | 5.1 fl oz151 mL |
| Pool liquid chlorine 10% | 0.6 fl oz19 mL | 1.3 fl oz38 mL | 3.2 fl oz95 mL | 6.4 fl oz189 mL |
| Household bleach 6% | 1.0 fl oz30 mL | 2.1 fl oz61 mL | 5.2 fl oz152 mL | 10 fl oz305 mL |
| Household bleach 8.25% | 0.7 fl oz21 mL | 1.4 fl oz43 mL | 3.6 fl oz107 mL | 7.2 fl oz214 mL |
| Cal-hypo 65% | 0.1 oz2.9 g | 0.2 oz5.8 g | 0.5 oz15 g | 1.0 oz29 g |
| Dichlor 56% | 0.1 oz3.4 g | 0.25 oz6.8 g | 0.6 oz17 g | 1.2 oz34 g |
| Trichlor 90% | 0.05 oz2.1 g | 0.15 oz4.2 g | 0.35 oz11 g | 0.75 oz21 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 | 1.1 oz32 g |
| Muriatic acid 31.45% | TA −10 ppm | 1.2 fl oz37 mL |
| Dry acid 93.2% | TA −10 ppm | 1.7 oz48 g |
| Muriatic acid 31.45% | pH 7.8 → 7.5 (TA 100, CYA 40) | 0.4 fl oz14 mL |
| Dry acid 93.2% | pH 7.8 → 7.5 (TA 100, CYA 40) | 0.6 oz18 g |
| Soda ash | pH 7.2 → 7.5 (TA 80, CYA 30) | 0.7 oz21 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 | 0.65 oz19 g |
| Stabilizer (CYA) | 0 → 40 ppm (new fill) | 2.7 oz76 g |
| Calcium chloride 77% | CH +10 ppm | 0.95 oz27 g |
| Calcium chloride 77% | CH +50 ppm (one step) | 4.8 oz136 g |
| Pool salt | 0 → 3,200 ppm (new fill) | 13.4 lb6.06 kg · 1 × 40 lb bags |
| Pool salt | +500 ppm | 2.1 lb946 g |
| Model | Capacity (manufacturer) |
|---|---|
| Intex Easy Set 8ft x 24in | 513 gal |
| Intex Metal Frame 8ft x 20in | 483 gal |
On this page (11 sections)
With 6% bleach, it takes 1 fl oz (2 tablespoons). This sheet is for small inflatable and frame pools, about 8 ft across, that run a filter pump and keep the same water for weeks. Doses this small are easy to overshoot, so measure with spoons instead of pouring from the jug.
Quick answer: chlorine for a 500 gallon pool (depends on product)
In the chlorine table above, +1 ppm is 0.5 fl oz (1 tablespoon) of 12.5% pool chlorine, 0.6 fl oz of 10%, or 1 fl oz of 6% bleach. Subtract your free chlorine (FC) reading from your target, then multiply the difference by the +1 ppm amount. Without stabilizer, keep FC at 2–4 ppm. Most pool chlorine labels say not to swim above 4 ppm.
Some popular pool apps won't accept a volume below 1,000 gallons, which leaves owners of small pools guessing. This sheet and the calculator are built for small volumes: every amount is shown in fluid ounces, milliliters, and, where it helps, spoons (1 fl oz = 2 tablespoons = 6 teaspoons).
Who this sheet is for: an 8 ft pool with a filter
About 500 gallons is the size of an 8 ft inflatable-ring or frame pool with a 20–24 in wall. Pools like these are often sold with a small cartridge filter pump, and that pump is what makes chlorine worth adding: it keeps the water moving and the dose spread evenly.
- No filter pump (a kiddie or splash pool): the CDC's advice for kiddie pools is to empty them daily instead of chlorinating. See kiddie pool chlorine.
- Filter pump you run every day: treat it like a backyard pool, with the routine below.
- A 500-gallon hot tub: hot water, jets, and bathers change the targets and the products. Use hot tub chlorine instead of this sheet.
Which cartridge your pump takes, and how often to rinse and replace it, is on Intex filter cartridge types and the Bestway Flowclear filter guide.
Dose table: chlorine by product for +1/+2/+5/+10 ppm
Read across the row for your product. For 500 gallons, the dry products come out in fractions of an ounce: +1 ppm is about 3 g of 65% cal-hypo or 2 g of 90% trichlor, less than a level teaspoon. A kitchen scale that reads grams is more reliable than guessing from the lid. Keep a set of measuring spoons only for pool chemicals, label them, and never use them for food.
Full-size 3-inch trichlor tablets are made for much larger pools. In 500 gallons, one tablet can push chlorine and stabilizer well past your target. Liquid chlorine or bleach is easier to dose here. If you prefer tablets, use small ones in a floater set to its lowest opening, as the label directs.
A daily routine for a small filtered pool
Small pools lose chlorine fast: the water is shallow, warms up quickly, and takes a lot of sun for its size. Find your own daily loss instead of guessing:
- Test FC in the evening, add chlorine to reach your target, and run the pump.
- Test again the next evening, before you add anything. The drop is your daily loss.
- Your daily dose is that loss times the +1 ppm amount. For example, a 2 ppm daily loss takes about 1 fl oz (2 tablespoons) of 12.5% pool chlorine a day.
Dose in the evening, after swimming, so the chlorine has the night to work before the sun breaks it down. Cover the pool when no one is using it: a cover keeps out leaves and bugs that use up chlorine.
How much shock: scale the label down to 500 gallons
The amount of shock comes from your product's label. Labels are usually written per 10,000 gallons, and 500 gallons is only one-twentieth of that (0.05). If a cal-hypo label says 1 lb per 10,000 gallons, your pool needs about 0.8 oz, or 23 g. A kitchen scale that reads grams makes that easy to weigh.
A 1 lb bag of 65% cal-hypo shock, emptied into 500 gallons, would add roughly 156 ppm of chlorine and about 110 ppm of calcium. Packaging is sized for backyard pools twenty times larger, so measure out what you need and close the bag. After a shock, keep everyone out of the water until chlorine is back at or below the swim limit on the label (often 4 ppm). See how to shock a pool for the steps.
pH and alkalinity: acid and baking soda
At this size, a teaspoon matters. Lowering pH from 7.8 to 7.5 takes only about 0.4 fl oz (a little over 2 teaspoons) of 31.45% muriatic acid when total alkalinity (TA) is 100 and stabilizer (CYA) is 40. Raising alkalinity by 10 ppm takes about 1.1 oz (32 g) of baking soda. Add half, wait 30 minutes with the filter running, retest, and then add the rest if you still need it. The muriatic acid calculator and the baking soda guide adjust these for your own readings.
Stabilizer, calcium, and salt
Stabilizer protects chlorine from sunlight. In a pool that sits in full sun all season, a little helps the daily dose last: 0.65 oz (19 g) raises CYA by 10 ppm, and 2.7 oz takes fresh water to 40 ppm (see the stabilizer calculator). With CYA at 40, keep FC at 3–5 ppm instead of 2–4. If you drain and refill every few weeks, you can skip it. Calcium is rarely worth adjusting in a vinyl or inflatable pool this size. The chart lists salt only for completeness. Small pools almost never use a salt chlorinator.
Pools that hold about 500 gallons
Intex lists 513 gallons for its Easy Set 8 ft × 24 in and 483 gallons for its Metal Frame 8 ft × 20 in. If you measure the Easy Set with a tape, the math gives about 602 gallons at an 80% fill. The real number is lower because inflatable walls lean inward. Use the maker's number. Other 8 ft pools are on the 8 ft round pool page.
At 500 gallons, fresh water is cheap. If the water turns green or stays cloudy after a shock, draining, scrubbing, and refilling is often simpler than a long treatment (our own reasoning, not a published rule).
Calculator preset to this volume
The calculator on this page is already set to 500 gallons. Enter your chlorine, pH, and alkalinity, pick the product you own, and it lists the steps in order with amounts for this volume. If your pool is a different size, change the volume or step up to the 1,000-gallon chart.
Safety with kids around. Keep children out of the water until chlorine is back in range after any dose, and store bottles out of reach. Never mix chlorine and acid. Always follow the product label. Poison Control: 1-800-222-1222.
FAQ
How much chlorine do I put in a 500 gallon pool?
For each 1 ppm: 0.5 fl oz of 12.5% liquid chlorine, 0.6 fl oz of 10%, or 1 fl oz of 6% bleach. With no stabilizer, the target is 2–4 ppm, so start from your test and add only the difference. More detail: how much chlorine to add.
How much shock for a 500 gallon pool?
Scale your shock product's label to 500 gallons, which is 0.05 of a "per 10,000 gallons" dose. A liquid chlorine label that says 1 gallon per 10,000 gallons works out to about 6.4 fl oz here. A cal-hypo label that says 1 lb works out to about 0.8 oz. Stay out of the water until chlorine is back at or below the label's swim limit.
How much muriatic acid for a 500 gallon pool?
About 0.4 fl oz of 31.45% acid lowers pH from 7.8 to 7.5 at TA 100 and CYA 40, and about 1.2 fl oz lowers alkalinity by 10 ppm. Dilute it in a bucket of pool water (acid into water) and pour it slowly with the filter running.
Sources
- Intex, product pages for Easy Set 8 ft × 24 in and Metal Frame 8 ft × 20 in, read 2026-09-29: intexcorp.com
- CDC, What you can do to stay healthy in kiddie pools: cdc.gov
- Taylor Technologies, K-1005 treatment tables (dose formulas): PDF
- How every number on this page is calculated: methodology