Hot tub water care

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.

Start here: hot tub chemicals for beginners

New tub, or new to owning one? Read what to buy and how to start up a fresh fill first. It covers the five products you need, the first-fill steps in order, and a weekly routine that takes a few minutes. Then find your tub's real volume on how many gallons your hot tub holds. Every number on this site depends on it, and the seat count alone won't tell you.

Calculators

The hot tub chemical calculator takes one test and gives an ordered plan for tubs of 50–1,500 gallons. Single-task tools are on the topic pages: a chlorine calculator with a chart for 200–700 gallons, a shock calculator that uses your combined chlorine, and pH and alkalinity calculators that account for your alkalinity. If you want to know how often to drain, the water change calculator gives an estimate from your gallons and how many people soak each day.

Sanitizer: chlorine or bromine

Both work. Chlorine is cheaper and easy to measure. Bromine holds up better at high pH and in hot water, and many owners prefer its smell. See chlorine doses by tub size and bromine levels and start-up. For weekly oxidizing and after heavy use, shocking a hot tub explains chlorine shock versus non-chlorine (MPS) shock.

pH and alkalinity

Jets and aeration push pH up in almost every tub. If yours keeps climbing, read why hot tub pH keeps rising. If it drops, see raising low pH. Total alkalinity (TA) sets how fast pH moves, so the alkalinity page is often the real fix. Targets in short: pH 7.4–7.6, TA 80–120 ppm, calcium 150–250 ppm, and water no hotter than 104 °F. The hot tub chemical calculator checks all of them from one test.

Problems

Most hot tub problems come from low sanitizer, high pH, a dirty filter, or old water. Start with the five-question check for cloudy or green water. Foam that builds when the jets run has different causes, covered in foamy hot tub water. Have an inflatable spa? Inflatable hot tub care covers models of 177–210 gallons.

Maintenance schedule

Test sanitizer and pH before each soak, and top up after. If the tub sits unused, test two or three times a week. Weekly: test alkalinity, shock, and rinse the filter. Monthly: soak the filter in cleaner. Every few months: drain, clean, and refill. The beginner's guide explains each step, and the hot tub maintenance schedule has a version to print.