I'm not an advocate of spending too much time washing my rainwear - after all it's just going to get filthy again on the next outing, but a trip to the laundromat can be a good thing and it does allow one the opportunity to audition for the next Levis advertisement.
An occasional wash will help prolong the functional life of your Storm Trooper or Flash Gordon. Unless you're in the back of beyond or suffering a power blackout you're best to avoid hand washing. Machines clean better, rinse better (it's important not to leave soap or detergent residue lurking in technical fabrics like HydroFoil™) ... and leave you to indulge in more enjoyable pursuits while your gear takes a spin. A warm cycle is the go. Try to avoid using cold-water detergents - they contain enzymes that are super-charged to brave the cold but can damage technical fabrics and may cause skin irritation too. Chlorine bleach is also a no-no. So it's quite the health spa on offer for your jacket. Select a soap-based product - ideally use a specific sport wash like Grangers Extreme Cleaner, Nikwax Tech Wash or our new favourite Atsko Sport Wash (from the makers of 'Sno Seal'). Around NZ$30 from most outdoor shops.
General wear 'n' tear, rolling around in the mud and subsequent washing progressively removes the 'Durable Water-Repellent Coating' (DWR) from the outside of the HydroFoil™ fabric. The DWR causes rain to bead and run off - enhancing the overall performance of the fabric by prolonging the time before the fabric 'wets-out'. Even when saturated, the fabric remains waterproof but wetting-out does inhibit its breathability so is best prevented. Aside from that it's unpleasant to feel like you're wearing a sodden Weet-Bix. The DWR is easily restored after each wash by chucking your jacket in the dryer using a warm (not hot) cycle. This 'recharges' the water-repellent treatment so it lasts a bit longer.
With time, the trick with the dryer no longer does its magic to revitalise the DWR. That's OK though as it is easy to reapply the treatment with a product like Atsko Permanent Water Guard, Grangers Extreme Synthetics or Nikwax TX Direct (around NZ$30-40 from most outdoor shops). A bottle is good for two or three rounds with your jacket. It's simple to use...