What Your Swim Kit Does, and When to Bin It

Six pieces of kit. What each one is for, what wears it out, and how to tell when it has stopped doing its job.

Most swimmers don't replace kit on a schedule. They replace it the session after it breaks — the goggle strap that snaps in warm-up, the costume that turns out to be see-through under the pool lights, the bottle that tastes of the inside of a bag.

 

The end of the summer break is the easiest time of year to get ahead of that. Kit has sat in a bag for six weeks, feet have grown, and everything is about to go back to five or six sessions a week. Whatever is wrong with your kit now will still be wrong with it in October.

 

Below are the six things worth checking. For each one: what it does, what wears it out, and how to tell when it's finished.

 

One thing worth saying up front: how long any of this kit lasts varies enormously. It depends on how often you swim, how heavily chlorinated your pool is, and how you dry and store things afterwards. Two swimmers can buy the same costume on the same day and wear it out months apart. So this guide is about the signs to look for, not dates to put in a diary.

Check One: The Training Costume

 

What it does

 

A training costume has a different job from a race suit. A race suit is built to hold you in and shed water for a handful of swims. A training costume has to sit in chlorinated water for two hours a day, six days a week, and still hold its shape.

 

So hard-wearing matters more than anything else. Most training costumes — one-piece suits, jammers, trunks and briefs — are made from polyester, or polyester mixed with a little stretchy fibre. The job is simple: stay where you put it, cause as little drag as possible, and not distract you for a whole session.

 

What wears it out

Chlorine, mainly. It attacks the stretchy fibre in the fabric rather than the polyester, and that fibre is what makes a suit spring back into shape. As chlorine breaks it down, the suit stops recovering. That's why an old costume feels loose even though it hasn't changed size.

Three things speed it up:

  • Heat. Tumble dryers, radiators and hot cars all cook the elastic.
  • Sunlight. Outdoor sessions and drying on a sunny windowsill both damage the fibres.
  • Leaving it wet in a bag. A screwed-up wet costume holds chlorine against the fabric for hours after you've left the pool.

A good habit is to use two costumes in rotation rather than wearing one out. Each gets a full day to dry, and the pair lasts longer than two suits used one after the other.

For younger swimmers there's a second clock running: growth. A costume can be in perfect condition and still be finished because its owner grew two inches over the summer.

 

When to replace it

  • It goes see-through when stretched. Pull the seat fabric gently — if you can see through it, so can everyone else under the pool lights.
  • The seat or chest has gone thin or bobbly.
  • Straps sag, or the back gapes however you adjust it.
  • The leg or arm elastic has stopped gripping and rolls as you swim.
  • It fills with water and balloons on push-off.

Fabric makes a real difference here. Costumes with more stretch in them tend to soften and lose their shape first; tougher all-polyester suits hold up for considerably longer, which is why they cost more up front and often work out cheaper over a season. Either way, go by the signs above rather than the calendar.

 

Shop training costumes

Check Two: Training Fins

 

What they do

Fins aren't there to make swimming easier. In a set they do four jobs:

  • Build leg strength. The extra surface loads the kick, so kick sets build power rather than just technique.
  • Loosen ankles. Stiff ankles are one of the most common limits on a swimmer's kick. Fins push the ankle through a fuller range of movement.
  • Let you swim faster than you can alone. That lets a swimmer feel the stroke rate and body position of a quicker swimmer, and learn to hold it.
  • Lift the hips, which makes it easier to hold a flat, straight line while drilling.

Short-blade fins are the usual choice for club swimmers, because they add work without slowing the kick down — it still feels like a swimming kick. Long-blade fins push much harder but force a slower, deeper kick, which suits beginners, snorkel work and swimmers coming back from injury more than race-pace training.

 

What wears them out

Usually nothing — fins tend to outlast their fit. The rubber lasts a long time, so the reason most swimmers need new ones is that their feet have changed. That's exactly why the end of summer is the moment to check.

Fins that are too tight cause cramp in the arch and calf, numb toes, and blisters on the heel and the top of the foot. Swimmers deal with it by curling their toes up inside the fin, which changes the kick and defeats the point of the drill. Too loose is nearly as bad: the fin slips on every kick, rubs the heel raw, and ends up on the pool floor.

 

Title

Coach's note

If a swimmer needs new school shoes, check the fins the same week. Feet do a lot of their growing over the summer, and fins are the item most often left a size behind.

Title

 

When to replace them

  • Pinching across the toes, or toes curling up to fit.
  • Red marks, blisters or rubbing after a session.
  • Cracks where the blade meets the foot — that's the part that bends, and it always goes first.
  • The foot pocket has stretched and won't stay on.
  • The pair no longer matches, because one was lost and replaced.

Rinse them in fresh water and dry them out of direct sun — sunlight is what turns rubber chalky and brittle. Don't store them folded or with weight on top.

 

Shop training fins

Check Three: Goggles

 

What they do

Goggles do more than keep water out. They protect your eyes from chlorine and from the chemicals that build up in it and make eyes sting. They're also the difference between swimming a set and guessing at one — you need to see the wall to turn, the clock to hold your times, and the swimmer in front to keep your place in the lane.

 

There are three main types. Training goggles have a bigger, softer seal and are built for comfort over long sessions. Racing goggles sit tighter into the eye socket with very little seal, for the smallest possible shape in the water. Junior and mask-style goggles use a larger seal and give a wider view, which suits swimmers still getting used to putting their face in.

 

Lens tint is practical rather than cosmetic: clear for indoor pools, smoked or mirrored for bright and outdoor water, amber for low light.

 

What wears them out

The anti-fog coating inside the lens goes first. It's an extremely thin layer, and wiping the inside of the lens with a finger or a towel takes it straight off. Once it's gone it can't be put back, and the goggles fog for good.

 

The seals go next. Rubber hardens and stiffens with chlorine, heat and sunlight, and a hard seal can't sit properly against your eye — so the goggles leak however tight you pull the strap. The strap stretches and loses its spring in the same way.

 

Mould is a storage problem rather than a wear problem. Goggles come out of the pool wet, go into a dark bag, and stay there. The seams of the seal and the strap adjusters are exactly the damp, sheltered spots mould likes, and once it's into the seams it's very hard to clean out. Since the seal sits right against your eye, mouldy goggles are worth replacing rather than scrubbing.

 

Title

Coach's note

Never wipe the inside of the lens. Rinse in cool water, shake them out, and let them dry outside the bag. Keep a spare pair in the bag too — goggles are the one thing that fails suddenly, mid-session.

Title

 

When to replace them

  • They leak however you adjust them, or need to be painfully tight to seal.
  • They fog constantly and clear for a length or two at best.
  • The seal feels hard, stiff or sticky instead of soft.
  • The strap has lost its stretch, or slips during a set.
  • There's mould, staining or a musty smell in the seal or strap.
  • The lens is scratched enough to affect what you can see.

A pair worn most days will always need replacing sooner than one kept back for meets. Rather than counting weeks, get into the habit of checking the seal and the strap now and then — they'll tell you far more than a date would.

Shop goggles

Check Four: The Club Cap

 

What it does

A cap does three practical jobs and one that matters just as much. It keeps hair out of your face and mouth, it cuts drag over your head, and it gives the goggle strap something to grip so it stays put through turns and dives. It gives hair some protection from chlorine too, though no cap keeps a head dry.

 

The fourth job is belonging. A club cap makes a squad look like a squad, and it lets a coach pick their swimmers out of a busy pool instantly. For a lot of younger swimmers, being handed the club cap is the moment they feel part of the team.

 

What wears it out

Mostly the material you chose, because that decides the lifespan:

  • Silicone is the standard: thicker, comfortable, easy to pull on and hard-wearing. It thins gradually rather than failing suddenly.
  • Latex is thinner, cheaper and cooler to wear, which suits long sessions in a warm pool. It also perishes fastest — going sticky or powdery — and tears easily. Avoid it if there's a latex allergy in the family.
  • Lycra and fabric caps are the most comfortable and the kindest to hair, but they soak up water and don't cut drag. Good for lessons and leisure swimming.
  • Racing caps are shaped to sit smoothly with fewer wrinkles, for meets rather than daily training.

Whichever you use, fingernails do most of the damage. Pull a cap on with the flats of your fingers, rinse it after training, and dry it inside out.

 

When to replace it

  • Thin or see-through patches, usually at the crown where it stretches most.
  • It's gone sticky or powdery — the classic sign latex has perished.
  • It's lost its stretch and rolls up at the edge or slides off mid-set.
  • Small tears at the rim, where nails catch pulling it on.
  • The club print has faded, or the design is out of date after a rebrand or a squad move.

Silicone outlasts latex by a comfortable margin, but treat caps as a wear item whichever you choose. It's worth keeping a spare in the bag and replacing on condition rather than waiting for one to split on the way to a session.

Shop club caps

Check Five: The Water Bottle

 

What it does

Swimmers get dehydrated without noticing, and it's the thing most squads get wrong. You sweat during a hard session just as you would on land, but you're surrounded by water and can't feel it, and the humid air on a poolside takes away the usual cues. Two hours can pass without a swimmer feeling thirsty at all.

 

It matters because losing even a small amount of fluid slows you down measurably — around two per cent of body weight is enough, and a long session reaches that easily. Everything starts to feel harder, technique falls apart late in a set, and you recover worse for the next morning. A bottle on the end of the lane fixes it, and it only works if a swimmer actually wants to drink from it.

 

What wears it out

Bottles fail from the inside, and nearly always at the lid rather than the body. Valves, straws, screw threads and seals stay damp and never see a brush, so they build up a slimy layer of bacteria that holds onto smells and tastes even after rinsing. Add squash or a sports drink and there's sugar in there feeding it.

 

The bottle itself lasts longer, but not forever. Plastic clouds over and picks up fine scratches, and those scratches give bacteria somewhere to sit where rinsing won't reach. A bottle that smells musty straight out of the cupboard isn't going to come clean.

 

The fix is a weekly strip-down: take the lid apart — valve, straw and seal separately — go through it with a bottle brush and a straw brush, then let it dry fully with the lid off. Putting a damp bottle away sealed is how the smell starts.

When to replace it

  • A musty or sour smell that survives a proper wash.
  • Dark staining in the valve, straw or under the lid seal.
  • The inside has gone cloudy or badly scratched.
  • The lid no longer seals and it leaks into the bag.
  • Any crack, however small — you can't clean inside a crack.

Treat a plastic bottle as a wear item — daily life in a kit bag takes its toll, and most need replacing before they look worn out from the outside. Insulated steel costs more but stands up to a lot more, keeps a drink cold through a long session and doesn't hold flavours. Either way, 500–750ml suits a standard session, and a second bottle is worth having for double days.

Shop water bottles

Check Six: The Swim Bag

 

What it does

A swim bag has a harder job than most bags. It carries a soaking costume and towel next to dry clothes and a phone — and for most swimmers, books and a laptop as well. It has to protect goggles from being crushed, swallow fins and a kickboard, and do all of it twice a day without the wet half ruining the dry half.

 

The features that actually matter:

  • A separate wet section, lined and ideally with drainage, so wet kit never touches dry clothes or electronics.
  • Ventilation. Mesh panels or vents let the inside dry out between sessions.
  • A padded goggle pocket, so they aren't at the bottom under a kickboard.
  • Properly padded straps. A full swim bag with a wet towel in it is heavy, and it's being carried by someone who has just trained hard.
  • A laptop or book sleeve, which is what lets one bag cover training and the school day.
  • A water-resistant base, because it goes down on a wet poolside every session.

A mesh bag is a different tool and worth having alongside it: it lives on the poolside, holds fins, paddles and a kickboard, and drains on the walk back to the car. It doesn't replace a proper backpack.

 

Title

Coach's note

The bag causes half the problems in this guide. Mouldy goggles, a fuzzy bottle and a costume that's lost its stretch all come from wet kit sitting in an unventilated bag overnight. Empty it after every session and everything else lasts longer.

Title

 

When to replace it

  • Zips that stick, catch or have lost teeth. Zips almost always go first, because chlorine corrodes them.
  • Seams splitting, especially where the straps join the body and take the weight.
  • Mould or a smell in the lining that won't wash out.
  • Fraying straps or failing stitching at the shoulder.
  • A base worn through from wet poolsides.
  • It no longer fits what the swimmer carries — common as juniors move up squads and start bringing fins, paddles and a snorkel.

A well-made bag with proper ventilation will outlast a cheap one by a wide margin, and how you look after it matters at least as much as what you paid. Rinse the wet section out now and then, and never leave kit in it overnight.

Shop swim bags

FAQs

How do I know when my training costume is finished?

There's no fixed answer on timing — it depends how often you swim, how heavily chlorinated your pool is, and how you dry it. Costumes with more stretch in them tend to go first, and tougher all-polyester suits hold up longer. Use the test rather than a date: stretch the fabric and look for see-through patches, and check whether the suit still springs back when you let go.

Why do my goggles fog up even though they're new?

Almost always because the inside of the lens has been wiped. The anti-fog coating is extremely thin and a single wipe with a finger or towel takes it off for good. Rinse goggles in cool water and let them air dry without touching the inside.

Can I clean mould out of goggles or a water bottle?

A bottle can usually be saved if you catch it early: take the lid fully apart and scrub the valve, straw and threads with a brush. Goggles are harder, because mould gets into the seams of the seal where no brush reaches, and that seal sits against your eye. If you can see mould in the seams, replace them.

Do I need short-blade or long-blade fins?

For club training, short-blade fins are the usual answer. They add work to the kick without slowing it down, so it still feels like a swimming kick. Long-blade fins push harder but force a slower, deeper kick — more useful for beginners, snorkel work and coming back from injury.

Is silicone or latex better for a swim cap?

Silicone for most swimmers: more hard-wearing, easier to pull on and more comfortable. Latex is thinner and cooler in a warm pool, which some swimmers prefer for long sessions, but it perishes faster and tears more easily. Avoid latex if there's any allergy in the family.

How much should a swimmer drink during a session?

Drink regularly rather than waiting to feel thirsty, because in the water thirst isn't a reliable signal. A 500–750ml bottle sipped at the end of sets suits most sessions. For long or double days, take a second bottle and consider a drink with electrolytes rather than plain water.