Ideal Hot Tub Water Chemistry: pH, Alkalinity & Sanitizer Targets

If you only memorize one thing about hot tub care, make it your target ranges. Here’s the cheat sheet, plus why each number matters.

The target ranges

• pH: 7.2–7.8 (ideal 7.4)
• Total alkalinity: 80–120 ppm
• Free chlorine: 3–5 ppm or bromine: 4–6 ppm
• Calcium hardness: 150–250 ppm
• Cyanuric acid (if using stabilized chlorine): under 30–50 ppm

Why each one matters

pH controls comfort and sanitizer efficiency. Below 7.0 the water turns acidic and corrosive; above 7.8 sanitizer loses punch and scale forms. Alkalinity is the shock absorber that keeps pH stable. Sanitizer is the only thing actively killing bacteria. Calcium hardness protects surfaces and equipment. And cyanuric acid — often overlooked — builds up from stabilized chlorine until your sanitizer simply stops working, which is one big reason hot tubs need a periodic drain and refill.

When numbers won’t cooperate

If you’re constantly chasing pH or sanitizer won’t hold, the water itself may be worn out (high total dissolved solids) and due for a refresh. Balanced water should be easy to maintain — if it’s a daily battle, something upstream is off.

Prefer to skip the upkeep entirely? Get a free quote from Bubble Balance — we keep hot tubs crystal-clear across Wilmington and the Cape Fear coast on a simple monthly plan. Or call (910) 264-3361.