Matt, I have spent the weekend working on my new trailer, washer, boiler, hose reels and all the rest of the gubbins I've bolted on - my mate thinks Wallace and grommit designed it ! Anyway I have thought about several ways to plumb the washer to the reel but also a simple way to be able to bring the boiler in without it being inline continiously. I have come up with a simple solution which if I can find rated componants would only be one valve