Many hygiene and cosmetic products can cause foaming bubbles in your hot tub. The use of shampoos, potions, hair spray, hair gel, deodorant and various other body and hair products can react with the churning hot water and cloud the water and cause surface foaming. To prevent this type of bubbling, shower prior to hot tub use and refrain from use of these products until after you have finished with your hot tub soak.
Your bathing suit can actually be the culprit of bubbly hot tubs. When you wash your bathing suit with laundry detergent to clean it and make it smell nice, you are actually creating a problem for your hot tub. The detergent that doesn't rinse out completely could come out in the hot tub and form bubbles and foam. To remedy this, wash your bathing suit an additional time without any detergent to rinse it clean before hot tub use.
There are two ways to remedy a hot tub that has become foamy or bubbly without having to drain the entire tub. A temporary fix is to cover up the problem with a foam control agent sold at pool and spa supply stores. This substance will reduce foaminess and bubbling but the problem may return when the substance dissipates. The better way is to super-sanitize the water. This requires adding large amounts of chlorine or bromine to the water to burn out all of the soapy agents or other impurities causing the bubbly problem. It is not recommended that you get in the hot tub when performing this method and wait until levels return to the normal level.
Each time chemicals are added to the water or soapy impurities are introduced the amount of total dissolved solids goes up in the hot tub. This is also known as TDS. This level rises continually regardless of what methods are used to prevent bubbling. The only way to reduce TDS is to drain all the water from the hot tub and clean or replace the filter. Performing this task about every 90 days should keep the water in good condition with normal use.