how do i reduce alkalinity in a spa?

Answer 1

Most spas require that you need to lower it if it tests above 7.8.The ideal pH range for spas is 7.2 to 7.8. If you drop the pH down below 7.2, it will begin to corrode your equipment and destroy the finish of the spa/tub.

Sodium Bisulfate is what is commonly sold in most spa stores to lower the pH. Muratic acid has also been used as a pH decreaser in hot tubs but it's been found to be a little too strong for use in small amount of water.

Here's a warning that I found on the back of the Sodium Bisulfate container;
"You should always dilute or dissolve pH control chemicals in a pail of water prior to adding it to the spa. Always add chemical to water, not water to chemical, to reduce splash hazard. The chemicals should then be added near the center of the spa with the jets running."

Hope this information was of some help to you. GOOD LUCK!

Answer 2

Make the pH drop by acidifying the spa. You could add some citrus juice to lower the pH.

Answer 3

Add distilled vinegar. Very inexpensive and easily obtained.