You invested in a quality pair of swim trunks. Maybe they fit perfectly, sit at exactly the right length, and hold their shape through a full day at the pool or beach. Then after one season, the elastic has gone limp, the color has faded, and the fabric feels stiff and rough.

This is not bad luck. It is preventable damage.

Most swimwear is made from polyamide and elastane, the same family of performance fabrics used in premium techno jersey clothing. These materials are engineered to move with the body and resist wear. But chlorine, salt, UV exposure, and incorrect washing methods degrade the fibers faster than almost any other combination of stressors in everyday life.

This guide gives you a complete, practical system for washing, drying, and storing swim trunks so they last for multiple seasons without losing fit, color, or structure.

Why Swimwear Degrades So Quickly

Swim trunks break down faster than most garments because they are exposed to three simultaneous stressors: chemicals, UV radiation, and heat. Understanding these mechanisms is the first step to preventing damage.

Chlorine attacks the fiber structure

Chlorine is the primary enemy of swimwear fabrics. Pool water typically contains 1–3 mg/L of free chlorine. At this concentration, chlorine molecules penetrate the fiber and break down the elastane, the component responsible for stretch and shape retention.

According to fabric care research, even a single hour of pool exposure without rinsing afterward can cause measurable degradation of elastane fibers over time. Repeated exposure without proper rinsing compounds this effect exponentially.

Salt water and UV radiation work together

Sea water is less chemically aggressive than chlorine, but salt crystals remain embedded in the fabric after drying. These crystals are hygroscopic, they absorb moisture from the air and create a cycle of moisture stress that weakens fibers over time.

UV radiation simultaneously breaks down the dye bonds in the fabric, causing color fading, and weakens the outer structure of the fiber. Wearing wet swimwear in direct sunlight combines both stressors at once.

Heat sets the damage

Heat, from tumble dryers, direct sunlight, or hot water washing, causes elastane to break down irreversibly. Once heat damage has occurred, no amount of fabric care can restore the original stretch. This is why tumble drying swim trunks even once causes permanent changes to their fit and structure.

How to Wash Swim Trunks: Step-by-Step

The correct method for washing swim trunks is to rinse immediately in cold water, hand wash with a mild detergent within 24 hours, and air dry flat away from direct sunlight. This routine takes less than five minutes and extends swimwear life significantly.

Step 1: Rinse immediately after use

The single most impactful action you can take is rinsing your swim trunks in cold fresh water within minutes of leaving the pool or sea. This dilutes and removes chlorine and salt before they have time to penetrate deeply into the fiber.

Use cool tap water, not warm, and certainly not hot. Cold water closes the fiber structure and limits chemical absorption. This step alone, applied consistently, can more than double the lifespan of a quality pair of swim trunks.

Step 2: Hand wash with a mild detergent

Machine washing is the second most common cause of swimwear damage after chemical exposure. The mechanical agitation of a washing machine stresses the seams and stretches the elastane in ways that cannot be reversed.

Hand washing is the correct method:

• Fill a basin with cool water (maximum 30°C)

• Add a small amount of mild detergent, avoid anything containing bleach, enzymes, or optical brighteners

• Submerge the swim trunks and gently agitate by hand for 60–90 seconds

• Rinse thoroughly until no detergent residue remains

• Never wring or twist the fabric, this distorts the fiber and stretches seams

If machine washing is unavoidable, use the delicate cycle at 30°C maximum, inside a mesh laundry bag, with a gentle detergent. Turn the trunks inside out first.

Step 3: Remove excess water correctly

After washing, gently press the swim trunks between two clean towels to remove excess water. Apply gentle pressure, do not wring or twist.

Rolling the trunks inside a towel and pressing firmly achieves effective moisture removal without mechanical stress on the fabric or seams.

Step 4: Dry flat, away from heat and sunlight

Always air dry swim trunks flat on a clean dry surface or on a drying rack in the shade. Hanging wet swimwear causes the fabric to stretch under its own weight, permanently distorting the shape.

Never use a tumble dryer. Never dry in direct sunlight. Both cause irreversible heat damage to the elastane fibers that give the garment its shape.

Comparison: Correct vs Incorrect Swimwear Care

How to Store Swim Trunks Between Uses and Seasons

Store swim trunks clean, dry, and folded in a cool, dry drawer or shelf. Never store swimwear damp, in direct sunlight, or compressed under heavy items. Correct storage between seasons is as important as correct washing.

Short-term storage (between uses)

After rinsing and drying following each use, fold the swim trunks neatly and store them in a dry location with good airflow. Avoid leaving them in a swim bag or sports bag overnight, enclosed damp environments accelerate mildew formation and odor.

End-of-season storage

Before storing swim trunks for the off-season:

1. Hand wash thoroughly following the method above

2. Allow to dry completely, at minimum 24 hours in a ventilated space

3. Fold along the natural seam lines to avoid permanent crease marks

4. Store in a cool, dry drawer or cotton storage bag

5. Avoid vacuum-sealed bags, compressed storage permanently distorts elastane

Keep swimwear away from any items that produce strong odors, as elastane fibers readily absorb ambient smells during long-term storage.

What to avoid during storage

Avoid storing swim trunks in:

• Plastic bags (trap moisture and cause mildew)

• Direct sunlight (UV causes color fading even without wear)

• Damp bathrooms (humidity degrades fabric over time)

• Compressed positions under heavy objects (permanent shape distortion)

Fabric-Specific Care: What Your Swim Trunks Are Made Of

Most quality swim trunks use a polyamide-elastane blend, typically 74–80% polyamide and 20–26% elastane. This combination delivers stretch, shape retention, and chlorine resistance, but only when cared for correctly.

Polyamide (also marketed as nylon) is highly resistant to abrasion and retains its shape well under normal conditions. It has moderate resistance to chlorine but degrades noticeably with repeated exposure and incorrect washing.

Elastane, often referred to by the brand name Lycra or Spandex, is responsible for the stretch and recovery that makes swimwear comfortable and form-fitting. It is significantly more sensitive to heat and chlorine than polyamide. Protecting the elastane component is the primary goal of any swimwear care routine.

Neycko's swim shorts, for example, use the same premium Italian techno jersey construction philosophy applied to summer swimwear, prioritizing fabric integrity, color stability, and long-term durability. Understanding your fabric composition helps you select the right care products and methods. The care label is always the authoritative reference.

"The biggest mistake men make with swimwear is treating it like casual cotton clothing. A quality swim trunk is a performance garment made from precision-engineered fibers. It deserves the same care you would give a technical sports kit."  Rick Ros, Neycko Menswear

Common Swimwear Care Mistakes and How to Avoid Them

Understanding what not to do is as valuable as knowing the correct method. These are the most frequently made mistakes that shorten swimwear lifespan:

Using fabric softener. 

Fabric softeners coat the fiber with a chemical film that reduces the elastane's ability to stretch and recover. Never use fabric softener on swimwear.

Washing at high temperatures.

Even 40°C is too high for most swimwear. The heat sets chlorine damage already present in the fiber and accelerates elastane breakdown.

Letting trunks dry in the sun while still wearing them.

UV exposure combined with the mechanical stress of wearing and the heat of skin contact is the fastest possible route to fabric degradation.

Sharing washing loads with denim or rough fabrics.

If machine washing is used, rough fabrics cause abrasion damage to the smooth surface of swimwear fabric. Always wash swimwear separately or in a mesh bag.

Not washing after every use.

Even if the water looked clean and the session was short, chemical and biological residues accumulate with each use. Washing after every wear is not excessive, it is correct maintenance.

Frequently asked questions about Washing and Storing Swim Trunks

How often should I wash my swim trunks?

Wash swim trunks after every single use. Even if the pool or sea appeared clean, chlorine, salt, sunscreen residue, and body oils accumulate in the fiber with each session. Rinsing immediately after use handles the chemical exposure, followed by a full hand wash within 24 hours.

Can I put swim trunks in the washing machine?

Hand washing is always preferred. If using a washing machine, select the delicate cycle at a maximum of 30°C, place the swim trunks inside a mesh laundry bag, and use a mild detergent without enzymes or bleach. Never machine wash on a standard or warm cycle. Never tumble dry.

Why do my swim trunks lose their shape so quickly?

Shape loss in swim trunks is almost always caused by elastane degradation from heat or chemical exposure. The main causes are tumble drying, washing at high temperatures, prolonged chlorine contact without rinsing, and storing while still damp. Correcting these habits immediately stops further degradation.

What detergent should I use for swim trunks?

Use a mild, enzyme-free detergent with no bleaching agents or optical brighteners. Products specifically formulated for delicate fabrics or technical sportswear are suitable. Avoid all-in-one detergents with built-in fabric softener. When in doubt, less detergent is better than more.

How do I remove chlorine smell from swim trunks?

Rinse thoroughly in cold fresh water immediately after pool use. For persistent odor, soak the swim trunks for 30 minutes in a basin of cold water with a small amount of white vinegar (roughly one tablespoon per liter), then rinse thoroughly and hand wash with mild detergent. Never use hot water to attempt odor removal, it sets the odor permanently.

How should I pack swim trunks for travel?

Ensure swim trunks are completely dry before packing. Fold along the natural seam lines rather than rolling, which can crease the waistband elastic. Pack in a breathable cotton bag rather than a sealed plastic bag. If you have used the trunks and cannot wash them immediately, a dry, ventilated cotton bag is significantly better than sealing them in plastic.

Conclusion

Swimwear care is not complicated, but it requires consistency. The core principle is simple: remove chemical exposure as quickly as possible, avoid heat at every stage, and store the garment clean and dry.

Rinsing immediately after every use, hand washing within 24 hours, drying flat in the shade, and storing in a cool dry environment, these four habits are the difference between swim trunks that last one season and those that remain in excellent condition for four or five years.

The fabric technology in quality swimwear is designed to perform. Your care routine determines whether it does.

Explore Neycko's swimwear collection and discover swim shorts built for durability, comfort, and style: zwembroeken wassen en opbergen — zo gaat je zwemkleding jaren mee