Inflatable Hot Tub Chemicals: The Complete Guide

The quick answer: an inflatable hot tub needs only a few things:

• a test kit;
• a sanitizer (most owners use chlorine: dichlor granules, optionally plus unscented bleach);
• pH decreaser and pH or alkalinity increaser;
• spare filters.

Keep chlorine at 3–5 ppm and pH at 7.4–7.6 (soak only at 7.2–7.8), test before every soak, and change the water every few weeks. Inflatables hold far less water than acrylic tubs, so small doses matter. Use your model's real volume in the calculator.

Why inflatables need a slightly different approach

• Small volume. Many 2–6 person inflatables hold a few hundred to about a thousand litres. Check your manual for the exact figure. A dose meant for a 400 gallon acrylic tub can overshoot an inflatable by double or more.
• Small filter. The cartridges clog fast and need frequent rinsing.
• No ozone or UV, usually, so the chemicals do all the work.
• Heavy use, hot water. Inflatables are often run at their maximum temperature (many are limited to about 40°C / 104°F) and used daily.
• Quicker water turnover. Contaminants concentrate quickly, so drains come more often.

Your shopping list

Brand starter kits (for example, the kits sold for Lay-Z-Spa or Intex) usually contain a version of this list. Just check the strengths and use your own volume for the doses.

Know your volume

Your manual or the box gives the capacity, usually in litres. "Four-person" and "six-person" vary a lot between models, so don't guess. If you only know the inside diameter and water depth of a round tub:

• Litres ≈ 785 × diameter² × depth (in metres).
• Example: a 1.5 m inside diameter at 0.55 m of water ≈ 785 × 2.25 × 0.55 ≈ 970 L.

Inflatable walls and seats curve, so treat this as an estimate and prefer the manufacturer's figure. See how many gallons in a hot tub.

How much chlorine? (per 1 ppm)

Multiply by the number of ppm you need. Raising a 1,000 L tub from 1 to 4 ppm takes 5.4 g of dichlor. Weigh your scoop once on a kitchen scale, so you know what a scoop really delivers.

First fill: step by step

1. Set up per the manual, on a flat, protected base. Fill with a hose, ideally through a hose pre-filter if you have hard or well water.
2. Start the heater and filter. Insert a clean filter.
3. Test the fill water for alkalinity and pH.
4. Adjust alkalinity to about 50–80 ppm, or your manual's range. Then adjust pH to about 7.4–7.6.
5. Add dichlor (or bleach, if you run without stabilizer) to reach 3–5 ppm. Run the bubbles or pump to mix, and keep the lid open briefly.
6. Test again before the first soak. Soak only when chlorine and pH are in range.

A simple routine

Before every soak: test chlorine and pH. Soak when free chlorine is 3 to 5 ppm and at least 7.5% of your CYA (bromine 4 to 6) and pH is 7.2 to 7.8, at least 15 minutes after adding anything (20 after pH decreaser); after chlorine, bromine or a shock, test again first. Above 5 ppm chlorine or 6 ppm bromine, wait and retest in an hour or two; never soak above 10 ppm chlorine or 8 ppm bromine, or with pH below 7.0 or above 7.8. Below 3 ppm chlorine (4 bromine), add sanitizer first; at pH 7.0 to 7.2, raise pH first; with CYA above 40 ppm, drain and refill. Hot tub limits based on CDC guidance and EPA product labels.

After every soak: add chlorine to cover what was used. Two people for 20–30 minutes uses noticeably more than one person for 10. Your test log will show your tub's pattern.

Every few days: rinse the filter cartridge with a hose. Inflatables' small filters clog quickly.

Weekly: shock (a larger chlorine dose, or MPS) and check alkalinity.

Dichlor-then-bleach: dichlor adds a little cyanuric acid (CYA) each time, about 0.9 ppm for every 1 ppm of chlorine. Once you've added roughly 33 ppm of chlorine from dichlor, CYA is about 30 ppm. Switching to unscented bleach for the rest of the fill keeps CYA from climbing. CDC recommends not using stabilizer in hot tubs because it slows chlorine down, which is why this method keeps it low; using bleach only from the start, with no stabilizer, is the other option (test before every soak, it fades faster).

Every few weeks: drain and refill. (gallons ÷ 3) ÷ bathers per day gives the interval. An 800 L tub (about 211 gallons) used by two people daily works out to about 35 days. See how often to drain a hot tub.

Common inflatable problems

• Cloudy water: low chlorine, high pH or alkalinity, or a clogged filter. See cloudy hot tub water.
• Foam: lotions, detergent in swimsuits, old water. See hot tub foam.
• Scale on the heater (hard-water areas): keep pH and alkalinity in range, and consider a scale inhibitor.
• Green or slimy: chlorine was too low for too long. Shock, scrub, and refill if it doesn't clear quickly.
• Strong chlorine smell: usually combined chlorine, not too much chlorine. Shock.

Safety

• Never exceed the tub's maximum temperature.
• Keep the lid locked when not in use.
• Store chemicals dry, cool, out of reach, and apart from each other.
• Never mix chemicals in a container. Add them one at a time to the water, with the pump running.

Presets for your model in Spa Calc

Pick your inflatable model in Spa Calc, or enter your litres, and every dose is sized correctly. Test before a soak and see whether your readings are in the soak range. The app also tracks the dichlor-then-bleach switch and counts down to drain day.

One hot tub? Every feature, free. No account, no ads, and iCloud backup is included.

Safety

• Keep chemicals out of reach of children and pets, and keep them out of the water until it is back in range.
• Never mix chemicals. Never add acid and chlorine together: mixing them releases toxic chlorine gas.
• Add chemicals to water, never water to chemicals.
• Store chemicals sealed, cool and dry, apart from each other.
• Read and follow the product label. It always comes first.