Does the chlorine level in your hot tub keep dropping? well? Here are three reasons why you can't keep your chlorine up: Number one: you have bofilm built up in your pipes. Contaminants build up inside your hot tub. Plumbing Over time, the more contaminants in your water, the more chlorine will get used up. So every 3 to 4 months, use a hot tub line, flush, and drain your hot tub.

Number two: you have too much combined chlorine in the water. You may have a lot of chlorine in the water, but it's already been used up or combined fighting contaminants. You need one to three parts per million of free chlorine to actively sanitize the water, use a non-chlorine shock AKA oxidizer to break up combined chlorine in the water, and number three: your water temperature is too high if your water stays consistently above 100. When you're not using it, your chlorine can dissipate quickly, lower the temperature when it's not in use.