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Why waterproofs stop working

Most hillwalkers assume a leaky jacket means the membrane has failed. In practice, that is rarely the case. Breathable waterproof fabrics rely on two things working together: the membrane itself, which blocks liquid water while letting vapour escape, and a durable water-repellent finish, usually shortened to DWR, on the outer face fabric. It is almost always the DWR that gives up first.

When the DWR fails, the outer fabric "wets out". Instead of water beading and rolling off, it soaks into the face fabric and sits there in a cold, heavy layer. Two things follow. First, the jacket feels damp and clammy even though no water has actually got through. Second, the soaked outer layer blocks the escape of your sweat vapour, so the membrane stops breathing and you end up wet from the inside. A jacket in this state is not finished — it needs washing and reproofing, not replacing.

Dirt makes things worse. Body oils, sunscreen, bog mud and the salt from your own sweat all contaminate both the face fabric and the membrane, attracting water and degrading the finish. Counter-intuitively, a filthy jacket is more likely to leak than a clean one.

Washing with a technical cleaner

Wash your waterproofs. Not often — every ten to fifteen days of hard use is about right for most people, plus an extra wash after any trip through peat bogs or anything gritty. The rules matter far more than the frequency.

• Use a specialist technical cleaner formulated for waterproof and breathable fabrics. Standard washing powder and liquid detergents contain surfactants, fragrances and optical brighteners that leave residues behind, and residues are what kill breathability.
• Never use fabric conditioner. It coats fibres with a waxy film that blocks the membrane's pores and strips the DWR. Even a trace from a previous load can do damage, so don't mix waterproofs in with a normal wash.
• Check pockets and close everything. Empty the map pocket of crumpled receipts, do up every zip, and fasten all velcro tabs so they don't snag the fabric or the mesh lining.
• Wash at 30°C on a gentle or synthetic cycle with a low spin. A slower spin is kinder to taped seams and laminated layers.
• Add an extra rinse cycle. This is the single most useful step and the one most people skip. It flushes out loosened dirt and any lingering detergent.
• Wash the trousers the same way. Knees and seat pick up more muck than any jacket panel, so they usually need it more.

Drying and reactivating the water-repellent finish

Once washed, the DWR often comes back to life without any additional product. The heat of a tumble dryer on a low setting, or a warm iron on the lowest setting through a tea towel, helps the polymer chains in the finish re-align and stand up again, restoring the beading effect.

Tumble dry on low for around twenty to thirty minutes, checking every so often — too much heat can damage taped seams, so keep it gentle. If you would rather not use a dryer, hang the garment to dry naturally and then iron it on a cool setting through a cloth. Either way, test the result: splash a little water on the shoulder. If it beads and runs off, you are done. If it soaks in flat and darkens the fabric, move on to reproofing.

Applying a fresh reproofing treatment

When the DWR is genuinely worn out, it needs replacing. There are two main approaches and they suit different garments.

• Wash-in proofer is easy and thorough. Add it to the machine on the correct cycle, following the bottle instructions. The catch is that it treats the inside of the garment as well as the outside, which can slightly reduce wicking and breathability. It suits trousers and general-purpose shells well.
• Spray-on proofer gives you more control. Hang the clean, damp garment up, spray evenly from about 20cm away, paying attention to shoulders, cuffs and hood, then tumble dry or iron to activate it. It is the better choice for jackets with a lining or a wicking backer.

Whichever you use, apply it to a clean garment. Reproofing over dirt simply seals the dirt in. Reproof at least once a season, and more often if you walk weekly in wet upland conditions.

Repairing tears, zips and seams

A small tear is not the end of a jacket. Deal with it promptly — a nick in a panel will only grow once it catches on a gatepost or a rucksack strap.

• Clean and dry the area first. Adhesive patches won't stick to a damp, muddy surface.
• Use an adhesive fabric patch on the outside for small cuts up to a few centimetres, rounding the corners of the patch so it doesn't lift. Press it firmly and leave it to cure overnight.
• For splits along a seam, a dab of seam sealant is the right fix. Apply thinly to both sides and allow it to set fully before you wear the garment again.
• Zips stiffen with grit and salt. Scrub the teeth gently with an old toothbrush and warm water, let them dry, then run a silicone-based zip lubricant along them. Avoid oil and wax products, which attract grit.
• Check the cord locks and hem drawcords. Replacing a frayed cord is cheap and stops the hem flapping in a wind.

Storage and habits on the hill

How you store waterproofs matters more than most people think. Hang them loose on a wide hanger in a dry, dark place rather than crushing them into a stuff sack for months. Long-term compression stresses the taped seams and laminate, and ultraviolet light gradually degrades the fabric.

Keep them away from radiators and hot airing cupboards, which dry out the DWR and can delaminate the layers. Airing a damp jacket after a wet day out is essential — never leave a sodden waterproof in the bottom of a rucksack to grow mildew.

Finally, build in a quick routine before each season. Wash them, reproof them, check the seams, the zips and the hem cords. Ten minutes of care in the autumn will keep a good jacket performing for years, and a well-maintained shell is warmer, lighter and far more comfortable than a wet one. Your waterproofs are doing some of the hardest work in your kit bag — they deserve the attention.