Test your hot-tub water with your test-strip kit every week to determine if you need to add sanitizer. After several tests over time, you may find that you always need to add lithium once a week. In that case, you can skip this step.
Add the amount of lithium stated on the instructions for the size of your hot tub. Typically, you'll start with 1 tbsp. per 150 gallons of water. After 10 minutes, check the water with a test strip to look for a chlorine reading of 5 parts per million (ppm) or higher. Low readings can occur with frequent use or many people using the tub at once. If the reading is low, add another tablespoon. Repeat until you reach the appropriate chlorine level. Do this process when nobody will be using the hot tub for at least eight hours. The chlorine level will decrease by the time you use the tub.
Wait for at least 24 hours. Then check and adjust the pH levels of the hot tub with your preferred product, if necessary. The reading should be around 7.6. Begin with 1 to 2 tbsp. of a pH-up or pH-down product per 250 gallons. If the reading is still off, wait at least 10 minutes before checking again and adding more product if needed.