Water Mixing Calculator

Calculate the perfect blend of hot and cold water for your hot tub.

Enter Your Water Information

Hot Water Temperature (°F)

Cold Water Temperature (°F)

Desired Starting Temperature (°F)

Total Hot Tub Volume (Gallons)

Hot Water Flow Rate (GPM)

Cold Water Flow Rate (GPM)

Cold Mixed Hot

Measure your hot and cold water temperatures to confirm they match your inputs.
Prepare your hoses and any needed water filters for filling.
Mix water according to the calculated ratio above.
Fill your hot tub gradually and monitor the temperature as you go.
Once filled, test and adjust your water chemistry before heating to final temperature.

Review Manufacturer Guidelines: Ensure your hot tub manual allows for preheated water mixing.

Test Water Temperature: Use a thermometer to confirm both water sources' temperatures.

Use Appropriate Equipment: Ensure hoses and water filters are rated for the temperatures used.

Monitor Water Chemistry: Plan to adjust pH, alkalinity, and sanitizer levels after filling.

Fill Gradually: Avoid a rapid fill to minimize thermal shock to your hot tub.