I use the Nikwax Tech wash (detergent substitute for waterproof kit, doesn't destroy the proofing), and stick it all in on 30. I've washed the bf's Altura Nevis jacket that way and no complaints. You can get the Nikwax range from outdoor shops, Decathlon etc. After a few washes the proofing does start to wear off (as I found out with my walking jacket in a downpour! It's probably had about 10-12 washes between reproofings though), but you can then reproof it with a wash-in reproofer from the range - again in the machine.
You shouldn't use ordinary detergent on waterproof/resistant kit, as it removes the proofing, but pure soap flakes are fine, as Radders says, and the tech wash is effectively just pure soap with a little reproofing agent added.