If you’ve been around online hot tub communities for any amount of time, you’ve no doubt heard of people using bleach to sanitize their hot tub. It’s often claimed to be a low cost and practical way to maintain free chlorine levels without adding CYA which can cause chlorine to be less effective. Hot tub dealers and manufacturers often claim that bleach can hurt a hot tub and irritate bathers.
What’s the truth? Will bleach hurt a hot tub?
Absolutely. If used incorrectly, liquid bleach can cause elevated pH levels that, left untreated, can cause scaling in the hot tub which can damage equipment. However, with a little care liquid bleach can make a lot of sense for sanitizing a hot tub.
Liquid bleach is indeed higher in pH than Dichlor. If you measure the pH a few minutes after adding it you’ll no doubt notice an upswing in the pH levels. As the chlorine reacts with contaminants, the reaction counteracts the rise in pH and makes it a bit more pH neutral. Nevertheless, over time the liquid chlorine can still push the pH beyond what is acceptable.
So if you’re going to use liquid chlorine, be on top of your pH. As long as you maintain a pH that creates balanced water, damage to equipment from usage is highly unlikely.
Do you have to use bleach to chlorinate your hot tub?
Absolutely not, but you do have to be aware that there are very few ways to maintain water for longer than a couple of months without raising CYA beyond a level that makes it impractical to properly sanitize.
If your hot tub sees infrequent usage and you’re willing to dump and refill it when the CYA far exceeds 50, then sticking to Dichlor can make sense. It’s important to not get dogmatic when maintaining a hot tub and use what works best depending on your usage pattern and appetite for dumping the water.