There is no need to to make it so complicated I run straight off the tap, I have been doing this for over two years now.
Sometimes the hose length can reach near 200 feet, and I clean to a height of 24ft.
I transport the di bottle on a little fold away trolley with the hose reel over the handle, I have experimented with two di bottles but as far as I'm concerned resin price isn't as issue as I claim it as a business expense.
My reasoning is that not all premises have an easily accessible tap in hose reach of where you need to work and some have different connectors so you would have to mess about with adapters and for other jobs I would need to attach to a tap inside.
I was thinking to produce water into a container as I am working.
(maybe start the day with the backpack full mounted on trolley and a couple of 25L containers full.)
From whats been said about working straight off the tap, I could do that where the tap is the right fitting and distance etc. and then use the back pack (mounted on trolley) where it's not.
Whilst I use the water in the back pack I could atttach a separate conainer to the tap via the DI and top up a spare. (I was thinking originally to be topping up the same container I'm working from as I work, but I guess that could get complicated.)
Is there somekind of shut off valve available that would stop the water once the container is full. (Like the ballcock in the toilet kind of thing)??