http://www.chainreactioncycles.com/SearchResults.aspx?Search=nikwax
Get some of the Tech Wash for a 40 degree wash and then use the spray on after. You then only need the Spry on once or twice a year if you keep using the Tech Wash. That should bring all your water proofing back.
On the label it recomends use on GoreTex and the Endura stuff (can’t remember the name).
Someone at Scottish Mountain Bike Gear moaned at me when I sent a jacket it in for repair because I’d washed it in Fairy Non Bio. He said that eventually the soap will wash all the water proofing away and the tape on the seams will come off. I’ve lost several jackets that way before being told about Nikwax and wondered what I’d been doing wrong.
You can get the Nikwax in bigger bottles and as a twin pack.
PS If you’ve got wooden or Kardine flooring DON’T spray the the shorts over that, best take them outside. We’ve been doing comedy slips on the floor for weeks now 😆 !