From time to time, it is advisable to re-waterproof the outer fabric of waterproof clothing. Waterproofing primarily serves to protect and maintain the outer fabric and enhances the material’s water-repellent properties. Water rolls off, meaning dirt particles cannot adhere to the clothing permanently. Water-repellent treatments wash out and need to be reapplied. You’ll know it’s time to do this when water no longer beads up, the outer fabric absorbs water and consequently becomes darker.