High tech clothing can require proper care and maintenance to maintain its DWR (durable waterproofing repellency) and over time dirt and grime can have an impact on the ability to remain waterproof.
Why dirt and grime can affect the DWR of your clothing
Dirt and particles can act just like a wick and pull rain and moisture through your high tech clothing giving the belief that the waterproofing has lost its effectiveness. The best way to try and resolve this problem is by using a proper fabric cleaner.
How to clean your high tech clothing with a fabric cleaner
The steps are very straight forward.