I'm slightly baffled behind this Nikwax tech wash thing.
What is this durable water repellency (DWR) they talk about.
Seems a bit snakeoily to me. TBH I've never dhobi'd a waterproof and my buffalos and montanes just get hoiked in the wash with everything else
Waxing and reproofing seems weird to me. Either its a jacket impregnated with stuff ie a wax jacket or its waterproof, or at a push ventile, which is supposed to have its own expand when wet to block ingress properties.
I want some science and I want it now!
Disclaimer: I am not a chemist, other nerds are available and will probably turn up in a minute.
Bear with me the point will be forthcoming.
You have doubtless seen the blokes who go around cleaning windows using the extendable poles with a hose hanging from the handle and connected to a tank of water in the back of a transit van. I went on a course for this gear with the original inventor of the system and he explained the water science to us.
Tap water is full of a collection of contaminants: Dirt; limestone; chemical traces; micro organisms. Water is basically a chemical mix and the contaminants hold the chemical mix stable. So, if you filter out all the contaminants water tends to become unstable and if you look at it under an electron microscope it looks like boiling nitric acid. Water try's to naturally make itself more stable by latching onto contaminants.
That is how the wash and reach window cleaning works, they use water that has had more or less everything filtered out so that it attracts the dirt off windows (to stabilise itself) and moves it away. Some of the window cleaning companies use heated water as this is even more aggressively looking for dirt to stabilise itself because the heat drives off molecules turning the water from H20 into H3O, making it more needy for contaminants (dirt) to stabilise itself.
Right, moving onto clothing: Your clothing as you wear it will get contaminated with schmutz on the surface over time. Rain is distilled water, so quite clean and free of contaminants therefore it is looking for contaminants to stabilise itself and it will soak into the contaminants on your jacket, or other clothing.
In order to stop the rain soaking into the surface of the jacket you need to remove the contaminants and this is traditionally done with a washing machine and detergent. The window cleaning lads do not use soap, or any additive to remove dirt, just pure water. Detergents in and of themselves can be quite aggressive destroying things like the nice PTFE goretex layer with repeated washes. Just washing with hot water will ordinarily do most of the cleaning, but adding a 'green' cleaning product or nikw@x will improve the cleaning quality. I use a green cleaning product......you get a bucket full and its cheaper than nikw@x.
So there you go, a boring diatribe about water. The company whose course I went on is Ionic, ex-RAF bloke owns the company, invented the system and the filtration methodology which is now used worlwide in everything from window cleaning, electronics production and bio-thingy's.
Ionic Systems - The Reach & Wash System
I do vaguely recall the threats from the Officers and NCOs set over me that they would rip a limb off and beat me with the soggy end if I was found to be wearing one, is this the Devil's Device to which they referred? 
