I haven't yet had to restore the water-repellency on any of my GoreTex stuff (waders and kayak top) but I know there is a proper way to do it. Here's some instructions I found on the http://www.gore-tex.com
website:Gore shell fabrics are treated with an ultra-thin treatment called DWR, a durable water repellent polymer applied to the outermost fabric layer. This treatment penetrates the fibers and lowers the surface tension of the fabric, causing water to bead up and roll off the outer layer of fabric, instead of being absorbed.
Water-repellent outer fabric provides additional insulation and prevents liquid from saturating your garment's outer fabric, a condition known as 'wet out' that can make you feel damp and clammy. Your garment may even feel like it's leaking, although it's not.
Regular wear and tear, plus exposure to dirt, detergents, insect repellant, and other impurities, causes DWR failure. DWR is not permanent on any fabric. Its effective life depends upon how you care for your garment and how rigorously it is used. The most effective way to maintain your Gore garment's water and stain repellency is to wash it, rinse it, and put it in your dryer. The washing removes contaminants and the heat from the dryer helps redistribute the DWR treatment on the fabric surface.
If water fails to bead up on the surface of your cleaned and tumble-dried garment, its DWR treatment has reached the end of its useful life. But don't worry: You can restore a Gore garment's durable water repellency by using a topical DWR revival treatment for outdoor fabrics, available at most outdoor retail shops. (Note: We do not recommend wash-in treatments.)
In addition, I've seen a spray-on treatment that is supposed to revive the GoreTex fabric. Simms sells it along with lots of fishing websites. It's called ReviveX and it's made by the McNett Corporation (http://www.revivex.com
). You wash your GoreTex item, spray on ReviveX and tumble dry.
A note of caution - I'm not sure I would want to throw my Simms GoreTex waders in the drier without first checking with Simms.
Good luck on restoring you GoreTex stuff. let us know how it goes. I might be doing something similar in the near future.