A jar of our hot tub treatment will clean spas from 300 to 500 gallons. If you have hard water, you need to use Crystal Clean once a year to keep your spa in top condition. First time cleaning may require more than 4 oz. per 100 gallons, or a second cleaning with Crystal Clean.
Add 4 ounces or more of Crystal Clean for every 100 gallons of spa water 2 to 3 days before draining and, when you drain out that old, dirty water, your spa will be cleaner than when it was new!