Chemical safety and product labels

Always follow the product label

Pool and spa sanitizers, shock treatments, and algaecides are pesticides registered with the U.S. Environmental Protection Agency. Federal law makes it illegal to use a registered pesticide in a way that is inconsistent with its labeling. Use only products labeled for pool or spa use, and follow each label's directions, maximum doses, precautions, and any "do not swim" or "do not enter until" instructions.

If anything on this site or in the app differs from a product label, the label wins. Some water care methods aim for chlorine levels higher than some labels allow for swimming, for example when stabilizer (CYA) is high or during algae treatment. We explain those ranges on the chlorine levels page. Whatever the range, don't enter the water until levels are within the limit on your product's label.

Pick chlorine products whose label has pool or spa directions. Some household bleach jugs have no pool directions on the label at all.

Calculations are estimates

Every dose depends on what you enter: pool or hot tub volume, test results, and the product's type and strength. Test strips read in steps, kits and store tests can be off, and volumes are often estimates. Add chemicals gradually, let the water circulate, and retest before adding more. If a dose looks unusually large, check the volume and the units first. The formulas and sources are on our methodology page.

Handling chemicals

• Never mix chemicals with each other, including different types of chlorine, or chlorine and acid. Mixing can release toxic gas or cause a fire or explosion.
• Add one chemical at a time, directly to the water, with the pump running. Wait at least 15 minutes between products, or longer if a label says so, and add them at different spots, several feet apart.
• Add chemicals to water, never water to chemicals. Pour acid slowly, close to the water surface.
• Wear eye protection and chemical-resistant gloves. Work outdoors, with the wind at your back.
• Store chemicals in their original closed containers, apart from each other, in a cool, dry, ventilated place out of reach of children and pets. Keep acid away from metal equipment and other chemicals.
• Use a clean, dry measuring tool for each chemical, and never share one between products.
• Hot tubs hold far less water than pools, so small measuring mistakes cause big changes. Double-check the volume and the units (teaspoons, tablespoons, ounces) before adding anything.

Storage, protective gear, and what to do after a splash are covered in more depth in our pool chemical safety guide.

Before swimming or soaking

• Test the water after every chemical addition. Enter only when levels are within the limits on the labels of the products you used, and after any waiting time a label requires.
• Pooldex never says that water is "safe". It shows your readings next to the swim limit from your product's label. In the app, that limit is 4 ppm of free chlorine until you enter the limit printed on your own product.

Health and emergencies

Pooldex does not give medical advice. If you are pregnant, have a medical condition, or are caring for young children, ask a doctor about hot tub use and water temperature.

Equipment and surfaces

Follow the instructions of your equipment and surface makers: heaters, salt cells, liners, plaster, and covers. Water that is out of balance can damage surfaces and equipment, and our terms of use explain the limits of our responsibility for that.

When to call a professional

Call a qualified pool or spa professional for electrical or equipment problems, water problems that keep coming back, suspected leaks, or any job you are not comfortable doing yourself. Public and commercial pools must follow state and local health codes and the instructions of a certified operator.

This page is part of our terms of use. How we handle data is in our privacy policy.