Treating kiddie pool water comes down to two choices: drain and refill daily, or sanitize the water so it stays clean for several days. For small pools under 100 gallons, daily dumping is the simplest option. For larger inflatable pools that take real time and water to fill, adding a small amount of household bleach keeps the water safe and swimmable for up to a week.
Figure Out Your Pool’s Volume First
Before you can treat the water properly, you need to know how many gallons you’re working with. Too little sanitizer won’t kill bacteria; too much will irritate skin and eyes. Most kiddie pools hold between 50 and 300 gallons, and some manufacturers print the volume on the box or in the product listing. If yours doesn’t, the math is straightforward.
For a rectangular pool, multiply length times width times water depth (all in feet), then multiply by 7.5 to get gallons. A 6-foot by 4-foot pool filled 1.5 feet deep holds about 270 gallons. For a round pool, multiply 3.14 by the radius squared (half the diameter, times itself) by the water depth in feet, then multiply by 7.5. A round pool 5 feet across and 1 foot deep holds roughly 147 gallons.
The Bleach Method
Plain unscented household bleach is the cheapest and most accessible way to sanitize a kiddie pool. You want regular bleach with no added fragrances, thickeners, or “splash-less” formulas, as those contain additives you don’t want kids soaking in.
When you first fill the pool, add ⅛ cup of bleach per 100 gallons of clean water. That’s 2 tablespoons. For a 200-gallon pool, use ¼ cup. Stir the water around to distribute it, then wait about 30 minutes before letting kids swim. Each day after that, test the water and add 1 teaspoon of bleach per 100 gallons as needed to maintain the chlorine level. You’re aiming for free chlorine between 2 and 4 parts per million, which is the same range used in full-size residential pools.
Pick up a pack of pool test strips from any hardware store or online. They cost a few dollars and take seconds to use. Dip the strip, wait the indicated time, and match the color to the chart on the bottle. You’re checking two things: free chlorine (2 to 4 ppm) and pH (7.4 to 7.6). If pH drifts too high, the chlorine becomes less effective even if the level looks right on the strip.
Non-Chemical Alternatives
If you’d rather skip bleach entirely, white vinegar and hydrogen peroxide offer gentler options, though neither sanitizes as aggressively as chlorine. Add 1 cup of white vinegar per 100 gallons of water to help prevent algae growth and reduce that slimy film that builds up on pool walls. Vinegar is antibacterial and antifungal, and it’s gentle enough for sensitive skin, but it won’t kill pathogens the way chlorine does.
Food-grade hydrogen peroxide (the standard 3% concentration you’d find at a pharmacy) is another option. Add ½ cup per 100 gallons no more than once or twice a week. It breaks down into oxygen and water, leaving no chemical residue. These alternatives work best for pools that get light use from one or two kids rather than a crowd, and they’re better suited for water you plan to change every two or three days rather than keeping for a full week.
When to Just Dump and Refill
The CDC recommends emptying small inflatable pools at least daily to prevent the spread of germs. That guidance is aimed primarily at untreated water. If you’re not adding any sanitizer at all, daily draining is genuinely the safest approach, especially for toddlers who are likely to swallow water or have diaper-related accidents.
For pools that hold under 100 gallons, draining daily is practical and avoids the hassle of testing and treating. Dump the water on your lawn or garden (plain pool water without chemicals is fine for plants), give the inside a quick wipe, and refill. The whole process takes five minutes for a small pool. If you’re treating with chlorine and testing daily, you can safely keep the water for several days before a full change.
Keeping the Water Clean Between Swims
Sanitizer is only part of the equation. Grass clippings, leaves, insects, sunscreen residue, and body oils all degrade water quality fast, and they eat up your chlorine in the process. A few simple habits make a noticeable difference in how long your water stays clear.
- Cover the pool. A fitted cover, tarp, or even a large shower curtain held down with clips keeps debris and sunlight out. Sun exposure accelerates algae growth and breaks down chlorine faster.
- Rinse kids off before they get in. A quick spray with the garden hose removes sunscreen, dirt, and sweat that would otherwise cloud the water within an hour.
- Skim the surface. A small handheld skimmer net (or a kitchen strainer in a pinch) lets you scoop out floating debris in 30 seconds.
- Keep it in partial shade. Direct sunlight warms the water, which accelerates bacterial growth, and it degrades chlorine. A shaded spot or a canopy helps on both fronts.
If the water turns green, that’s algae. Drain the pool completely, scrub the interior with a brush and a mild cleaning solution (a splash of bleach in a bucket of water works well), rinse thoroughly, and start fresh. Trying to treat visibly green water with more chemicals is a losing battle in a pool this size.
Bromine as an Alternative Sanitizer
Bromine is the same type of sanitizer used in most hot tubs, and it works well in small warm pools too. It breaks down more slowly in warm water than chlorine does, which means you don’t need to re-dose as often. It’s also less irritating to skin and eyes and doesn’t produce that strong bleach smell. The tradeoff is cost: bromine typically runs about twice the price of chlorine. For a kiddie pool where you’re using tiny amounts, the price difference is negligible, so it’s worth considering if your kids have sensitive skin. Bromine tablets dissolve in a small floating dispenser, making dosing almost hands-off. One important note: bromine breaks down quickly in direct sunlight, so it works best for covered or shaded pools.
Scrubbing and Storing at Season’s End
When you’re done with the pool for the season, or even for a stretch of days, drain it completely and flip it over to dry in the sun. Any moisture left trapped in folds will grow mold and mildew during storage. Before putting it away, scrub the interior with a solution of water and a small amount of bleach or white vinegar, rinse well, and let it dry fully. Store it in a cool, dry place rather than a damp garage or shed. Folding it loosely rather than tightly reduces the chance of cracking along crease lines, especially for vinyl pools in cold weather.