Chlorine, salt water
and how to survive them
Swimwear rarely wears out. It gets destroyed — usually by chlorine, heat and sunlight, and usually faster than it needed to.
Updated 26 July 2026 · 5 min read
What actually causes the damage
| Cause | What it does |
|---|---|
| Chlorine | Breaks down elastane, so the waistband loses its stretch |
| UV light | Fades dye and weakens fibres over long exposure |
| Heat | Destroys elastic fastest of all — tumble dryers are the worst offender |
| Salt crystals | Abrasive once dry; they cut fibres from the inside as the fabric flexes |
| Sunscreen and oils | Stain permanently, especially on light colours |
Note what is missing from that list: swimming. The actual use barely wears swimwear at all. Everything that shortens its life happens after you get out of the water.
The one habit that matters
Rinse in cold fresh water as soon as you can. Not later, not at home if home is three hours away — at the poolside tap or the beach shower if there is one.
Chlorine keeps reacting with elastane for as long as it is in contact with it. Salt does its damage once the water evaporates and leaves sharp crystals behind in the weave. Both problems are solved by the same thirty seconds of cold rinsing, and doing it immediately is worth far more than any washing routine afterwards.
If you do nothing else, do this. A cold rinse straight after swimming does more for the lifespan of swim shorts than every other piece of care advice combined.
What not to do
- No tumble dryer. Heat is what kills elastic. One hot cycle can do more damage than a season of swimming.
- No hot wash. Cold or lukewarm only.
- Do not wring them out. Twisting stretches and breaks the elastic threads. Squeeze gently instead.
- No fabric softener. It coats synthetic fibres and reduces how well they shed water — it makes quick-dry fabric slower to dry.
- No bleach, no iron.
- Do not leave them in a bag. Damp fabric in a closed bag grows mildew, and the smell does not come out.
- Do not dry them on a hot radiator or in full sun all day. Shade with airflow beats direct heat every time.
The routine that works
- Rinse in cold fresh water immediately after swimming.
- Squeeze — do not wring — to get the bulk of the water out.
- At home, hand wash in cold water with a little mild detergent. A machine on a cold delicate cycle inside a mesh bag is acceptable if you would otherwise not wash them at all.
- Rinse again.
- Hang or lay flat in the shade with air moving around them.
Do not fold them away until the waistband is completely dry. It is the thickest part of the garment and the last to lose moisture, and it is where mildew starts.
What a realistic lifespan looks like
Treated this way, a decent pair of polyester swim shorts will last several seasons of regular use, and the print will fade before the fabric fails. Treated badly — chlorine left in, tumble dried, stored damp — the same pair will have a slack waistband inside a single summer.
The difference between those two outcomes is almost entirely that first cold rinse.