Hot Tub Chemicals

Fill the tub, run the pump so the water circulates, then correct in order: total alkalinity to 80 to 120 ppm first, pH to 7.2 to 7.8 second, free chlorine to 3 to 5 ppm last. Alkalinity comes first because it anchors pH, and correcting pH before it will simply drift back.

Dose with the pump running, leave the cover off for 15 minutes afterwards, and retest after a couple of hours rather than immediately. Never mix chemicals together, and always add them to water rather than water to them. The starter kits carry the full set for a first fill.

Dose to the reading rather than to a fixed spoonful, because the right amount depends on your tub's volume and on where the level currently sits. Add a small amount, circulate, retest, and repeat. Overshooting is far more work to correct than undershooting.

Follow the dose on the pack for your water volume, which is on the product page for each item here. Keep a note of what you added and what the strips read afterwards, because after two or three cycles you will know your own tub's pattern and stop needing to think about it.

Hold pH between 7.2 and 7.8. Below that the water becomes corrosive to the heater and pump seals; above it, chlorine loses effectiveness and scale forms on the element.

Correct total alkalinity to 80 to 120 ppm first. Alkalinity is what resists pH movement, so with it in range pH stays put, and with it out of range pH will swing back however often you adjust it. Hot water naturally pushes pH up over time, so expect to bring it down more often than up.

Both, for different jobs. Granules dissolve within minutes, so they are what you use when a test comes back low and you want the level corrected before anyone gets in. Tablets dissolve slowly in a floating dispenser and hold the level steady between tests, which is what stops it dropping in the first place.

Most people settle into granules to correct and tablets to maintain. Whichever you use, the target is the same: free chlorine between 3 and 5 ppm, checked with test strips rather than judged by eye. The starter kits include both alongside the pH and alkalinity adjusters.

Chlorine to sanitise, pH increaser and reducer to hold the range, alkalinity increaser to stop pH drifting, and test strips to see where you are. Those five cover it. The starter kits bundle them so nothing arrives late.

After that, clarifier, foam remover and algaecide are occasional rather than routine. A spare filter matters more than any of them, since cartridges last four to six weeks and a blocked one shows up as cloudy water and slow heating.