People put tennis balls in hot tubs for one very simple reason: to soak up body oils and lotions that float on the surface. And according to those who swear by it, this actually helps — at least a little.

Read on to learn more about why people do it, how well it works, and where it fits in with real hot tub care.

Why People Put Tennis Balls in Hot Tubs

Here’s what’s going on. When people soak, all the stuff on their skin — you know, the body oils, lotion, sunscreen, and makeup residue — tends to come off in the water. And since hot tub water is warm and still, it all tends to gather in an oily layer that just hangs out on the surface, eventually sticking to the sides and turning into that grimy scum line nobody loves scrubbing.

The reason a tennis ball comes into play here is that it happens to have a fuzzy outer layer that can actually grab onto some of that oil. The idea is that you simply drop one in, float it around right where the problem is (usually near the filter or skimmer area where those scum lines often show up), and it absorbs some of that oil out of the water.

It’s basically a cheap, DIY version of the scum balls and oil-absorbing sponges you see in spa stores.

Does It Actually Work?

The old tennis-ball-in-a-hot-tub trick can definitely help keep your water clean. But don’t expect miracles.

A tennis ball will absorb some surface oils, especially if it’s clean and not already saturated. You’ll even see it darken slightly as it does its thing, which is your sign it’s picked up something. Then, if you swap it out for another clean one, it’ll keep helping.

But with that said, it’s not a replacement for a deep water-care solution. Filtration, sanitizer levels, and balanced water chemistry are still going to be doing most of the heavy lifting when it comes to keeping your tub clean. 

The tennis ball is more like tidying up the surface, not fixing the whole room.

How to Use a Tennis Ball in a Hot Tub

If you want to try it, here’s how to use a tennis ball in a hot tub:

1. Use a brand-new, clean tennis ball. Not one that’s been dragged across a court or chewed by a dog.
2. Let it float when the hot tub isn’t in use. No need to sit on it while soaking.
3. Check it every so often. If it looks grimy or heavy, it’s done its job.
4. Rinse it or replace it. Most people just replace — it’s a tennis ball, not a family heirloom.

Think of this as optional. Nice to have, easy to try, but not something you rely on to fix water problems.

Want Help Keeping Your Hot Tub Water Clear?

Little tricks like this can help at the surface level, and sometimes that’s enough to make the tub look better day to day. But long-term, clear water comes from consistent care, which includes maintaining clean filters, proper sanitizer levels, and not letting things slide for weeks at a time.

If you need a hand staying on top of maintenance and water quality so you’re not relying on hacks alone, we can help. Contact Clark Pools and Spas today, or drop by the store if you’re around.

The tennis ball can stay, but it shouldn’t be doing all the work.