How to Test Hot Tub Water

What You'll Need
Test kit

Average hot tub water will run at 102ºF while a pool typically runs at 82ºF. The heat of the water removes more of the grease from your skin and can encourage even faster bacterial growth if the chemical balances of your water are not kept correct at all times. 

Step 1 – Understand Your Test Kit

If you did not receive a test kit with your hot tub you must ensure that you obtain one before the tub is put into use. Read the instructions on the test kit very carefully. Many modern kits now use simple paper strips to test the water. This is a lot easier and faster than the chemical test kits.

Step 2 – Sanitizer

Sanitizers are simply the chemicals that keep the water free of bacteria. The two most common are chlorine and bromine. Dip your test strip in the water and compare the color for the sanitizer against the color key card. Chlorine should show between 1.5 million and 3 million parts per million (ppm).

Step 3 – Ph Balance

Ph balance is the acidity of your water. If your Ph balance is low the water in your tub is too acid. This will stop the sanitizer working properly and can do damage to exposed metal parts of the tub. It could also cause skin and eye problems. If your Ph balance is high the water is too alkali which does the same sort of damage as too acid except there is scale formation in parts of the tub. Dip your test strip in the water and compare the color for Ph against the color key card. Ideally the range should be between 7.2 and 7.8.

Step 4 – Total Alkalinity

Total alkalinity is what allows you to adjust the Ph level in your hot tub. Again you test by dipping a test strip in the water and comparing the resulting color with the color code card. The normal level is from 80 ppm to 120 ppm.  

Step 5 – Hardness

Hardness is a measure of the amount of minerals dissolved in the water. These minerals include calcium and magnesium. Too much hardness will result in scales forming and the water becoming cloudy. Too little hardness can lead to the corrosion of exposed metal parts in the tub. For an acrylic finish tub the color of the test strip after dipping should show a value of between 100 ppm and 250 ppm. While other results of your test kit can be adjusted within the tub, the hardness of your water will need to be lowered by a separate water softener if it is too high.

Your kit will have full instructions on what to do to correct levels that are outside of the ideal. The instructions should also give you the best order in which to do the tests, total alkalinity, Ph and sanitizer.