Why Is Calcium Falling out of My Hot Tub Water?

Causes

• Water collects varying amounts of minerals from soil and air. These minerals typically include calcium, magnesium and other common elements. The level of these minerals in solution accounts for the water’s “hardness” or softness,” with hard water containing a higher mineral content and soft water containing only sodium ions, according to the Free Drinking Water website. When the water in a hot tub contains more calcium than it can hold in solution, the calcium deposits itself on surfaces and in pipes as a solid product known as limescale.

Complications

• Limescale can create serious problems for hot tub owners. In addition to leaving a chalky white residue on the surfaces where people sit or place their feet, excess calcium and magnesium can build up around the inner diameter of the plumbing pipes serving the hot tub. This buildup effectively narrows the usable inner surface of the pipes, allowing less water to travel to and from the hot tub. In extreme cases the limescale can eventually block the pipe completely, making the hot tub unusable. Accumulations of limescale can also cause the heater or pump to malfunction, according to hot tub retailer Splash & Relax.

Solutions

• Hot tub owners struggling with a limescale problem must reduce the hardness of the water in the hot tub periodically. Pool and hot tub suppliers sell additives that can correct the water to an acceptable hardness level and help prevent calcium buildup. ThermoSpas notes, however, water hardness issues may indicate an underlying issue with the water's pH level, which plays an important role in controlling relative hardness or softness. Hot tub owners should ensure that the water maintains a pH level between 7.2 and 7.8 before proceeding with hardness or softness treatments.

Considerations

• While hard water can promote limescale, overly soft water can also cause problems for hot tub owners. Water containing too little calcium can damage a hot tub by pulling other metals out of its surroundings, promoting corrosion of metal pipes and other components. This corrosion can not only impair the hot tub’s functionality, but it can also leave stains and discolorations. Fortunately, just as water softeners can correct limescale problems, other additives can boost the calcium level of hot tub water to the desired balance, preventing this unsightly corrosion.