Swimming Pool Filtration Types Explained

How do you keep a pool clean? There are different pool filtration systems and the differences matter.

Here's a plain-language breakdown of the six main methods, how each one works, and what it feels like to swim in.

The short version

There are six common ways pools keep their water clean, starting with the familiar standard and moving toward the lower-chlorine options you'll find throughout the Saltwater Wanderer directory:

• Traditional chlorine uses chlorine added directly to the water to sanitize it.
• Salt-chlorine generators turn dissolved salt into a low, steady stream of chlorine.
• Mineral and low-salinity blends lean on minerals like copper and silver, with only a little salt or chlorine.
• UV filtration uses ultraviolet light to kill off bacteria and viruses.
• Oxygen filtration uses active oxygen to break down contaminants instead of chlorine.
• Ocean-fed pools pump filtered seawater straight from the source.

If that's all you came for, you're set. If you want to know which one suits you, keep reading.

Traditional chlorine

This is the baseline, the system every other method on this list is measured against. Chlorine is added to the water directly, usually as tablets, granules, or liquid, where it dissolves and goes to work killing bacteria, viruses, and algae.

It's popular for good reason. Chlorine is cheap, widely available, and it sticks around in the water, so it keeps protecting the pool between top-ups. That lasting residual is exactly what makes it the default for big, busy public pools.

The downsides are the ones everyone knows. Higher chlorine levels are what cause stinging eyes, dry skin, faded swimsuits, and that unmistakable smell, which is actually the chloramines that form when chlorine reacts with sweat and sunscreen. None of the methods below get rid of chlorine entirely in every case, but they all aim to use a lot less of it.

Salt-chlorine generators

This is what most people picture when they hear "saltwater pool," and it's the most common type by a wide margin.

The pool water has salt dissolved in it, and that water passes through an electrified cell called a generator. The cell uses the salt to produce chlorine on the spot, in a low and steady amount. So there is still chlorine doing the sanitizing work, just less of it than you'd find in a traditional pool, and it's generated continuously instead of being dumped in by hand.

The payoff is water that feels softer and smells far less like a public locker room. The trade-off is the equipment: the cell needs occasional cleaning and eventually replacement, and the water carries a mild salinity, though nowhere near as salty as the ocean.

Are these pools chlorine-free? No. They make their own chlorine instead of having it added, but it's still a chlorine pool at heart. If anyone tells you a salt pool has zero chlorine, they're mistaken.

Mineral and low-salinity blends

Mineral systems take a different route. They use metals, usually copper and silver, to help keep the water clean, paired with a small amount of salt or chlorine to finish the job.

Copper is good at controlling algae and silver helps with bacteria, so together they handle a lot of the work that chlorine would otherwise do alone. That's why these pools need so little of it. The result is gentle water that's easy on skin and eyes, with a noticeably lighter chemical load.

The catch is upkeep of a different kind. The minerals get used up over time and need topping off, and the system still relies on a small chlorine or salt assist rather than running on minerals alone. It's a blend, not a replacement.

UV filtration

UV filtration skips chemistry almost entirely. Water flows past an ultraviolet lamp, and the light neutralizes bacteria, viruses, and chloramines, the compounds responsible for that harsh "chlorine smell," without adding anything to the water.

The important thing to understand is that UV treats the water as it passes the lamp, but it leaves nothing behind to protect the water afterward. That's why you'll almost always see UV running alongside a small amount of another sanitizer rather than handling everything by itself. Think of it as a powerful assistant rather than the whole crew.

For swimmers, the appeal is obvious: less of the smell, less of the sting, and far fewer chemicals overall.

Oxygen filtration

Oxygen systems sanitize using active oxygen instead of chlorine. Rather than relying on a chlorine residual, they introduce powerful oxidizers, things like hydroxyl radicals and hydrogen peroxide, that break down bacteria, algae, and organic gunk and render it harmless. Instead of using chemicals like chlorine to do the killing, the oxygen molecules break down and remove the harmful substances directly.

The big draw is comfort. It's chlorine-free, odorless, and doesn't irritate skin or eyes, which makes it a favorite for swimmers who react badly to chlorine or just can't stand the smell. It also doesn't form chloramines, the byproducts behind red eyes and that telltale pool stench.

There's a real trade-off, though. Active oxygen acts fast but degrades quickly, especially in heat and direct sunlight, so it doesn't hold continuous protection in the water the way chlorine does. In practice that means more frequent treatment, and on larger or sun-soaked pools it's often paired with a touch of another sanitizer or a copper system to keep a lasting residual. On smaller, shaded, or indoor pools it can carry the load on its own.

Ocean-fed pools

These are the rare ones, and frankly the reason a lot of people end up on this site in the first place.

An ocean-fed pool pumps filtered seawater directly from the sea. No salt added, no chlorine generated, just the ocean itself, screened and circulated. It's about as close as you can get to swimming in the sea while still standing in a pool.

You'll only find these along coastlines, and they come with their own quirks. Tides, weather, and water temperature aren't something a filter can iron out, so the experience shifts with the conditions. But that's also the charm. No two swims are quite the same.

How to pick

Here's the quick comparison:

• Traditional chlorine — high, lasting chlorine; familiar feel, can sting and smell; most public and home pools.
• Salt-chlorine — low, steady chlorine from dissolved salt; soft, mildly salty water; found almost anywhere.
• Mineral blend — very low chlorine with minerals and a touch of salt or chlorine; gentle, light water; resorts and wellness-focused pools.
• UV filtration — minimal chemicals with a small residual sanitizer; clean, low-smell water; modern builds, often paired.
• Oxygen — none to minimal chemicals, sometimes a small assist; soft and odorless; smaller, shaded, or indoor pools.
• Ocean-fed — no added chemicals, real seawater; coastal locations only.

If you want something widely available and low-fuss, a salt-chlorine pool is the safe bet. If sensitive skin is your main concern, look at mineral, UV, or oxygen setups. And if you're chasing the genuine sea-swimming feeling, ocean-fed is the holy grail, just be ready to travel for it.

A few common questions

What's the difference between a saltwater pool and a chlorine pool?

A traditional chlorine pool has chlorine added to it directly. A saltwater pool makes its own chlorine from dissolved salt. Same sanitizer, different delivery, and usually a gentler swim.

Do saltwater pools have any chlorine?

Salt-chlorine pools do, just at lower, steadier levels. Mineral and UV systems use very little, oxygen systems use little to none, and ocean-fed pools use none at all.

Which type is best for sensitive skin?

Mineral blends, UV, and oxygen-filtered pools tend to be the easiest on skin and eyes, since they keep added chemicals to a minimum.

Are ocean-fed pools safe?

Yes. The seawater is filtered before it reaches the pool. The main variables are natural ones, like temperature and tide, rather than anything to do with cleanliness.

Find your kind of water

Every pool in the Saltwater Wanderer directory is tagged by how it's filtered, so you can sort by what matters to you, whether that's a low-chemical oxygen pool near home or a genuine ocean-fed pool worth booking a trip around.