How to Fill & Balance Your Hot Tub Water

A step-by-step guide for first fills, water changes, and clean starts — designed for modern hot tubs and real-world water conditions.

Serving Santa Rosa & surrounding communities

Filling and balancing your hot tub water correctly from the start makes ongoing maintenance easier, improves comfort while soaking, and helps protect internal components. This guide walks through the recommended process for a new installation or a full drain and refill.

What You’ll Need

  • Garden hose (with optional pre-filter)
  • Water test strips or liquid test kit
  • Sanitizer (chlorine or bromine)
  • pH increaser and pH decreaser
  • Alkalinity increaser

Step 1: Fill the Hot Tub Properly

  1. Turn off power to the hot tub before filling.
  2. Remove the filter cartridges. If possible, place the hose into the filter housing to reduce trapped air in the plumbing.
  3. Fill the tub to the minimum water level indicated by the manufacturer.
  4. Reinstall the filters, then restore power once the tub is fully filled.
Using a hose pre-filter can help reduce minerals and metals, especially in areas with hard or mineral-heavy water.

Demonstration video (Wellis Spa example)

Step 2: Circulate and Test the Water

Once filled, allow the hot tub to circulate for at least 20–30 minutes before testing. This ensures the water is evenly mixed and temperature stabilized.

  • Test total alkalinity first
  • Test pH second
  • Test sanitizer level last
Ideal targets: pH 7.2–7.6 • Alkalinity 80–120 ppm

Step 3: Adjust Alkalinity and pH

Always adjust alkalinity before pH. Alkalinity stabilizes pH and helps prevent rapid swings.

  1. Add alkalinity increaser if levels are low.
  2. Run jets for 25–30 minutes to circulate.
  3. Retest, then adjust pH if needed.
  4. Circulate again before final testing.

Demonstration video (Wellis Spa example)

Step 4: Add Sanitizer

Once pH and alkalinity are balanced, add sanitizer according to the product label. Maintain sanitizer levels within the recommended range before using the hot tub.

Common Mistakes to Avoid

  • Adding multiple chemicals at the same time
  • Skipping circulation between adjustments
  • Chasing exact numbers in a single session
  • Testing water before it has fully mixed

Once your water is balanced, ongoing care becomes simple and predictable.

Weekly and monthly water care guides coming soon.