How do I stop chlorine ruining my swimwear?

Swimwear fails in a specific and recognisable way: it goes baggy, then thin, then translucent when wet, and tiny white hairs appear on the surface. Those hairs are broken elastane filaments, and everything that causes them is avoidable.

Step by step

1. Rinse before you get in as well as after.A costume soaked in fresh water absorbs less chlorinated water, because the fibres are already saturated. It is a small effect but it is free.
2. Rinse in cold fresh water immediately after swimming.This is the important one. Chlorine keeps reacting as the fabric dries, and the concentration rises as the water evaporates. Rinse thoroughly in the pool showers, before it dries.
3. Never leave it damp in a bag.A wet costume rolled in a towel in a warm bag is chlorine, heat and moisture working on elastane for hours. If you cannot wash it at home immediately, at least get it out of the bag and hanging.
4. Hand wash in cool water with a gentle detergent.Cool, never hot. A small amount of gentle liquid detergent, or a dedicated swimwear wash. Squeeze the water through rather than rubbing.
5. Deal with sun cream and body oil.Sun cream oils degrade elastane and also stain white and pale swimwear yellow. Wash the costume properly, with detergent, after any use with sun cream, and treat marks promptly with a small amount of washing-up liquid worked into the fabric.
6. Press out the water in a towel.Wringing a swimming costume stretches and breaks the elastane. Roll it in a towel and press.
7. Dry flat, in the shade.Ultraviolet light degrades elastane and fades the dye, so drying a costume on a hot poolside or in full sun does the same damage as the chlorine. Flat, in shade, with air moving.
8. Rotate two costumes if you swim regularly.Elastane recovers when it is dry and unloaded. Alternating gives each one a full day to recover and roughly doubles the useful life of both.

Tips

• Chlorine-resistant swimwear exists and is worth the money if you swim in a pool more than about once a week. It is usually polyester or PBT rather than nylon and elastane, and it lasts several times longer.
• A costume that has gone see-through when wet has lost fibre density through elastane breakdown and abrasion. Nothing restores it.
• Sitting on rough poolside tiles and concrete abrades the seat of a costume faster than any amount of swimming. Sit on a towel.
• Salt water is gentler than chlorine but still needs rinsing out, because salt crystals are abrasive as the fabric dries and moves.
• Hot tubs are the worst environment of all: high chlorine or bromine concentration plus high temperature. Expect a costume used regularly in one to have a short life.

Common mistakes

• Waiting until you get home to rinse — The chlorine concentrates as the fabric dries in the bag. Rinsing at the pool is what preserves the fabric.
• Wringing the costume out to get it dry quicker — It stretches and snaps the elastane filaments that are already the most vulnerable part.
• Drying swimwear over a radiator or in direct sun — Heat sets the elastane in its stretched state and UV degrades it. Both are as damaging as the chlorine.
• Machine washing swimwear on a normal cycle — The agitation, the temperature and the spin all attack the elastane, and the hooks and zips of other garments snag the fabric.

Questions people ask