Can I fill my Hot Tub with Softened water?

Many customers ask us…

* Can I use soft water in my Hot Tub?

* Can I reduce Calcium in my Hot Tub?

* Why is there limescale in my Hot Tub?


This post should answer all of the questions.

Water’s degree of hardness refers to the water’s mineral balance.

Swimming pools and hot tubs are dependent upon proper levels to keep their moving parts, heating elements, pipework and other components running efficiently, so filling your hot tub with softened water requires immediate balancing treatments.



Hard and Soft Water – The Difference

Calcium and magnesium are the minerals that most directly contribute to water hardness. Measurements of these and other minerals in the water supply are noted in parts-per-million, or ppm.

Hot tub water that is too soft can be corrosive to metal, while water that is too hard can cause damaging scaling.

Finding the right balance and maintaining that balance through water testing and treatment is the key to a healthy, long-lasting hot tub.


When Filling Your Tub

Since many water supplies tend to lean toward excess hardness, homeowners often add a water softener to the incoming pipe.

Water from a home softener is not properly balanced for hot tubs, however, so if you must fill your hot tub with a softened water supply, you’ll need to harden it up with treatments before it causes any problems.

The ideal calcium level for water in a hot tub is 200 to 400 ppm, but before you add a product like Liquid Calcium to your newly filled tub, you must first get the alkalinity and pH in line. Start with Alkalinity.


The Perfect Balance

Alkalinity is a measure of all carbonates, including calcium, and it determines the water’s ability to maintain a steady pH.

Low alkalinity requires the addition of a base, like sodium carbonate, (Alkalinity Increaser) and high alkalinity requires the use of an acid. (Ph & Alkalinity Reducer)

Fiberglass hot tubs are best balanced at between 170 and 250 ppm alkalinity. Once that level is stable, it is then possible to fine tune the pH levels using Ph Increaser or Ph Reducer until your water is steady at 7.2 to 7.8 ppm.


Finally, when you’ve balanced your water’s chemistry to the recommended levels, you can harden your water with a calcium additive until you hit the recommended window.

Hardness and alkalinity levels should be tested weekly.


See our other FAQs, for more information on how to balance Alkalinity and Ph.