Foam happens when hot tub water thickens and air jets activate tiny bubbles. Most of the causes of foam come from common contaminants getting into the water: hair care products, body lotions, deodorant, makeup, laundry detergent, and drinks.
An anti-foam chemical provides some quick relief from the problem, but it doesn’t fix it. When household or cosmetic products contaminate water, the only real fix is to drain your spa, spray down the inside and wipe it clean.
Be sure to not leave any cleaner inside the spa before you refill it.