My Acrylic Hot Tub Has Calcium Deposits

Causes

• Calcium deposits are usually chalky white scales on the walls and heating elements. In severe cases, grainy white crystals of calcium carbonate are felt along the floor. These deposits are caused by a high calcium content in the water combined with a high pH. Calcium carbonate precipitates out of the alkaline water and sticks to surface of the tub and heating elements.

Alkalinity and pH

• Alkalinity and pH are two different concepts in water maintenance. In the pool industry, alkalinity is a measure of the water's ability to neutralize acid and keep the pH within the proper range. pH is a measure of how acidic or alkaline the water is. Calcium carbonate formation requires both the alkalinity and the pH of the water to be too high.

Prevention

• Most hot tub providers recommend adding a sequestering agent to balance pH of the water on a weekly basis. This should only be used with water with less than 150 ppm of calcium. Otherwise the water will become cloudy. The calcium levels can be easily checked with test strips or for a more accurate result, a solution test kit. These kits can be purchased at any spa or pool maintenance supply retailer. Most spa sellers also sell acidic solutions that can be used to regularly maintain the appropriate pH in the water. If calcium levels are higher than 250 ppm, the hot tub should be drained and refilled with fresh water.

Removal

• Create a weakly acid solution with vinegar and water. Spray onto the calcium deposits and wipe off with a soft rag or a cleaning pad approved for use on acrylic surfaces. The weak acid dissolves the deposit, making it easy to remove. Rinse with clean water to remove the acid. Refill the hot tub with fresh water.