There are a number of reasons why spa water foams:
1. You have detergent in the water.
Detergent can be found in your swimming clothing, hair, body, sunscreen, lotions and oil based scent.
2. You have oils in your water.
Oils can come from bathers not showering before they enter the spa or swim spa. It can come from un-approved spa scents being used. If you are using scents make sure they are an approved spa aromatherapy and not oil based.
3.pH and Alkalinity not correct
When your spa water goes out of balance it can start to foam as well as cause damage to your spa or irritating rashes on bathers. Test often using test strips designed for your chemical system.
How do I fix the problem?
Step 1. Check. You pH and Alkalinity using test strips and adjust the pH and alkalinity into the ok range.
Step 2. Soak your filters in filter cartridge cleaner, hose out and put back into the spa, that should fix the problem.
Make sure that whatever you wear while in your spa has not been washed in detergent or make sure you double rinse the garment.
Don't use oils in your spa.
Have a shower before entering the spa.
Keep your water in balance.
Keep your spa filters clean.
If your spa water is over 4 months old, use a pipe degreaser ,dump the water, clean and soak your filters in an approved filter cleaner and then refill your spa with fresh water.
If all these suggestions don't work there is a product that will get rid of the foam and it is called Anti Foam. Follow the directions on the product label for best results.