Products that don't belong in the hot tub are the number one cause of foam. Showering before using the hot tub or keeping certain things out of the tub will often reduce or eliminate foaming. To keep hair gels, mousse, shampoo and hairspray from entering the water, keep long hair out of the tub by tying it back. Showering just before entering the tub will eliminate hair products as well as body lotions and deodorants--two more leading causes of foam. Also, leave moisturizing until after using the spa, rather than before. Using less or no deodorant will also help. Even if your body is clean, a good rinsing won't remove all the residual laundry soap from your swim suit. Washing your suit more often, but without soap will solve this particular problem. Dropping food or drinks into the water is another potential foam producer. Finally, and maybe surprisingly, the very chemicals you use to keep the spa clean may be adding to the foam. Cheap chemicals or excessive amounts of chemicals both can cause foam.
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Total Dissolved Solids
Another cause of hot tub foam is Total Dissolved Solids. Chemicals take all those foreign elements in the water--body lotions, dead skin and so on--and turn them into residue that clings to the air-jet bubbles. When these rise to the surface, they give the appearance of foam. Once saturated, there is only one solution: Change the water. Before it gets to that point, use the one-third rule. Using the right chemicals, cleaning filters often and according to your hot tub instructions and replacing a third of your tub water each month will keep down Total Dissolved Solids.