Chlorine Proof vs. Chlorine Resistant Swimwear: Why Your Swimsuit Went Baggy After One Season

The short answer: chlorine resistant swimwear is made of nylon and spandex that has been treated to last longer in chlorine, but it is still spandex, so it still breaks down, just more slowly. Chlorine proof swimwear is made of PBT and polyester with zero spandex, so there is nothing for chlorine to destroy. If you swim in a pool every week, choose chlorine proof.

Why your swimsuit went baggy after one season

You paid good money for a swimsuit. A few months of pool days later, it's baggy, faded and a little see-through. And the label said "chlorine resistant." It's not you. It's the fabric.

Most swimsuits get their stretch from spandex (also sold as Lycra® or elastane). Spandex is what makes a suit hug your body, and it is also the weak point. Three things break it down:

• Chlorine. Every pool swim exposes your suit to it. The CDC recommends keeping at least 1 ppm of free chlorine in pools and at least 3 ppm in hot tubs, three times the pool minimum.
• Sunscreen. Lotions and oils soak into the fibers.
• Sun and heat. Hot decks, hot tubs and strong sun speed up the damage.

As the spandex fibers weaken, the fabric loses its snap-back. That's when a suit starts to sag, thin out and fade.

"I'm so happy I found these modest … skirts. I've gone through a boat load of suits due to chlorine."

— Kimberly G., on the Swing Skirt 21"

Chlorine resistant vs. chlorine proof: two different fabrics

Chlorine resistant

• Made of nylon + spandex.
• The spandex is treated to hold out longer. Even premium chlorine resistant spandex, such as XTRA LIFE LYCRA®, is rated by its maker to last up to 10 times longer than regular spandex.
• Longer, but not forever. It is still spandex, so it still breaks down, just more slowly.

Chlorine proof

• Made of PBT + polyester.
• Zero spandex.
• Nothing for chlorine to destroy.

PBT (polybutylene terephthalate) is a polyester with natural stretch built into the fiber itself, so it doesn't need spandex. In short: resistant slows the damage, proof removes the reason for it.

Pool, ocean or lake

Chlorine proof fabric is made for the pool, and it is just as good at the beach:

• Its tight knit means sand doesn't get trapped.
• Salt rinses right out under fresh running water.
• Prints and colors stay vivid for years.

As one HydroChic customer told us: "2 years later with heavy chlorine pool use, fabric doesn't fade."

Which one do you need?

• You swim, do water aerobics or soak in a hot tub every week: choose chlorine proof. Shop our Water Aerobics & Pool Swimwear.
• You mostly swim at the beach, a lake or on vacation, with an occasional pool day: chlorine resistant will serve you well, and chlorine proof will simply last longer. Shop our Cruise, Beach & Water Park Swimwear.

A suit that lasts longer is also better for the planet. According to WRAP, wearing a garment just 9 months longer can cut its carbon and water footprint by 20–30%.

"They wear well and do not bag or sag in the pool."

— a HydroChic customer

"I bought my first piece several years ago. It's still in great shape. … My chlorine proof items have held up for several years."

— Jamie H.

Before you buy, check the tag

If the fabric content lists spandex, elastane or Lycra, it is not chlorine proof, whatever the label on the front says. At HydroChic, every product page lists the exact fabric, so you always know what you are getting.

FAQ

Is chlorine resistant the same as chlorine proof?

No. Chlorine resistant fabric contains treated spandex that breaks down more slowly. Chlorine proof fabric contains no spandex at all, so chlorine has nothing to break down.

How can I tell if a swimsuit is chlorine proof?

Read the fabric content. Chlorine proof swimwear is typically PBT polyester with no spandex, elastane or Lycra listed.

Does chlorine proof swimwear still stretch?

Yes. PBT has stretch built into the fiber itself, so the fabric moves with you without spandex.

Can I wear chlorine proof swimwear in the ocean?

Yes. It holds up well in salt water and sun. Just rinse it in fresh water after you swim.

Why are hot tubs harder on swimsuits?

The CDC recommends at least 3 ppm of free chlorine in hot tubs, three times the pool minimum, and the water is hot. Both speed up the breakdown of spandex.

Shop all chlorine proof swimwear →

Sources: CDC, Operating and Managing Public Pools, Hot Tubs and Splash Pads; The LYCRA Company, LYCRA XTRA LIFE® fiber; WRAP (Waste and Resources Action Programme), Sustainable Clothing Guide.