White, grainy buildup on your spa's walls indicates a hard water issue. Calcium is the main culprit, although lime may also be to blame. Mineral deposits increase in hot water, especially in areas with hard water or if your spa's balance isn't properly maintained. Prevention is simpler than curing, so identify the causes early so you can keep the buildup from becoming a problem.
The fill water for the spa. Calcium and lime levels vary by region, but if you have hard water, buildup may become an issue.
Calcium chloride. In areas with soft water, this is added during filling. Although it's more soluble than the calcium typically found in hard water, using too much can result in buildup.
Spa sanitizers. Many use forms of calcium, which can lead to buildup if you add them too often or over apply.
Evaporation. Even with carefully managed calcium levels, increased evaporation during hot, dry days may leave behind deposits. Covering the spa when it's not in use prevents this.
Prevention is the best option, and it begins by carefully managing the pH levels in the spa. Spa water is most comfortable and most resistant to buildup when it's near near pH neutral and only slightly on the alkaline side. Maintain the pH level between 7.0 and 7.6 to keep it as neutral as possible.
If the pH rises above 7.6, you will need to add a solution to lower the pH level. Most of these contain sodium bisulfate, a minor acid. Test the water before making any additions and monitor it daily so you can adjust the pH as needed. You can also add a descaling solution to the water with the pH adjuster, to help manage any buildup.
A Fresh Start
If you can't get the water in balance, it may be time for a fresh start. You can test the calcium along with the pH during your daily water balance testing. If the calcium levels stay high, a refill may be the best option.
Most spas are best drained and refilled at 12 week intervals, so you only have a major problem if the calcium level is raising more rapidly than this. If this is the case, call in a spa technician to help monitor the calcium levels and to troubleshoot the causes. This can prevent the need frequent drainage.
Once you have the buildup, it's difficult to remove without damaging the spa's finish. If you try to do it yourself, use a mineral remover and cleaner made for spa use and avoid any abrasive pads. It's usually a better choice to bring in a professional like one from Anchor Pools & Spas to do the job to prevent damage. They can also check your water lines and spa heater to make sure buildup isn't causing any hidden damage in these areas.