Why does my waterproof jacket soak through when it is not leaking?
The membrane is usually fine. What has failed is the water-repellent finish on the outer fabric, and a saturated outer face stops the jacket breathing, so your own sweat condenses inside it.
- Difficulty
- beginner
- Time
- 10 min
- Read
- 4 min
Short answer
The outer fabric has a durable water repellent finish — DWR — that makes rain bead and roll off. When that wears off, the face fabric soaks up water instead. The membrane still keeps liquid water out, but vapour from your body can no longer escape through a saturated outer layer, so it condenses on the inside and runs down. It feels exactly like a leak and it is not one. Clean the jacket, then reproof it.
This is the single most misdiagnosed fault in outdoor clothing, and it sends people out to replace jackets that need an hour of attention. The tell is that you get wet in a way that feels clammy and general rather than dripping and localised, and that the outside of the jacket looks dark and soaked rather than beaded.
Step by step
- Look at the outside of the jacket in the rain.A working DWR makes water bead and run off, and the face fabric stays visibly dry. A failed DWR lets water spread into a dark wet patch that soaks the whole panel. This observation alone diagnoses it.
- Note where it goes first.Shoulders, upper back, forearms and anywhere a rucksack strap or a hip belt rubs. DWR is worn off by abrasion, so it fails first exactly where the jacket is rubbed most.
- Understand the three layers.Outer face fabric with the DWR on it; a waterproof breathable membrane bonded behind it; and a lining or a printed backer inside. Only the membrane is waterproof. The face fabric is there to protect it and to shed water.
- Understand why a wet face fabric stops breathing.The membrane moves water vapour by diffusion, driven by the difference in humidity across it. A saturated face fabric is a continuous film of liquid water on the outside of the membrane, and that removes the gradient. Vapour stops moving out and condenses on the inside instead.
- Recognise the symptoms of wetting out versus a real leak.Wetting out: general clamminess, damp inner surfaces over a wide area, worse when you are working hard, dark saturated outer fabric. Real leak: water at a specific point, usually a worn seam, a failed seam tape, a zip or an abraded spot, and it happens regardless of exertion.
- Understand what kills DWR.Abrasion, ground-in dirt, body oil, insect repellent, campfire smoke and — very commonly — ordinary laundry detergent residue left in the fabric, which is a surfactant and actively attracts water.
- Fix it in the right order.Wash the jacket with a technical cleaner to remove the contamination first, because reproofing over dirt does not work. Then apply a fresh DWR, then activate it with gentle heat as the manufacturer directs. There is a separate guide for the process.
- Know when it really is the membrane.Visible delamination — the inner surface bubbling or peeling away from the face fabric — or seam tape lifting means the jacket has a genuine construction failure. Those can sometimes be repaired at a specialist but not by reproofing.
Tips
- Washing a technical jacket in ordinary detergent, and especially with fabric conditioner, is a fast way to kill the DWR. Both leave a hydrophilic residue that draws water into the fabric.
- Wetting out is worse when you are working hard, because you are producing more vapour that now cannot escape. A jacket that feels fine on a gentle walk and soaks you on a climb is wetting out.
- A jacket that has been stored compressed for years may have a crushed or contaminated DWR that recovers substantially with a wash and a tumble on low, before any reproofing product is needed.
- Softshells have no membrane and are water-resistant only. They rely entirely on DWR, so they wet out sooner and reproofing matters more.
Common mistakes
- Buying a new jacket because the old one is leaking — In the great majority of cases the membrane is intact and only the DWR has gone. A wash and a reproof restores the performance for a fraction of the cost.
- Reproofing a dirty jacket — DWR needs to bond to clean fibre. Applied over body oil and dirt it beads unevenly and washes straight off.
- Assuming a waterproof rating means it will never wet out — The hydrostatic head number describes the membrane. It says nothing about the DWR on the face fabric, which is the part that wears out.
Questions people ask
How often does DWR need renewing?
It depends entirely on use. Heavy use with a rucksack might need it every few months; light use once a year or less. Judge by whether water still beads, not by a schedule.
Does washing a waterproof jacket damage it?
Not with the right product. Washing with a technical cleaner is part of maintaining it, because dirt and body oil are what destroy the DWR. Washing with ordinary detergent or conditioner does damage it.
Can I just wear a jacket that wets out?
In light rain, yes — the membrane still keeps rain out. In sustained rain or hard exertion you will get wet from the inside, and in cold conditions that is a real problem.