Wow, I had no idea the US military is that well equipped. Somehow I always thought the military have to tough it out while the civilians get all the fancy outdoor tech.

You wouldn’t happen to have the official Marines Goretex washing manual handy, would you?

No, no book, Sir. I guess I just followed the crowd at chow time.

Wash in Nikwax Tech Wash, hang dry.

Why would you think so?

They have the combined budget of the next 10 militaries.

Price is NOT a high priority for their procurement team, unlike most shoppers.

The US Army also issues Gor-TEX branded jackets and boots. You get them your first week in the Army, and every year you get a clothing allowance you can use to get new Gor-TEX products.

The term to google is "durable water repellent" (DWR). In sport shops you can buy sprays or washing liquids to treat the jackets.

https://en.m.wikipedia.org/wiki/Durable_water_repellent

Also note each jacket has a different thickness of the gore-tex layer which conditions how many hours of rain it can withstand.

dwr != gore-tex wash. DWR is the cheaper/non-permanent waterproofing solution (likely containing PTFE) to add waterproofing to an otherwise non-waterproof jacket (or to make the outer layer waterproof)

Traditional gore-tex outerwear is made of 3 layers. The middle layer is the goretex, but the other layer is some fabric treated with a DWR that needs to be maintained for the jacket to work well (or the outer layer saturates with water and prevents the middle layer from breathing).

So yes, you need to treat most goretex jackets with a DWR periodically.

Yeah. Nikwax is a big brand.

You can also get "Shakedry" Gore-tex products, which don't have an outer layer needing DWR treatments at all.