Here is a little idea that I've found works quite well:
When you unplug your WFP from whatever its connected to, what happens for the next few minutes? The water gradually runs out of the pipe, just as you set it in the van, leaving a nice big puddle on the van floor.
Here is a tip, use a small non-return valve at the top of the pole:
Connect it before the pipe splits off to go to the jets. Now when you unplug the pole pipe, the water stays in the pipe!
And when you start to use it again, you dont need to wait for a couple of seconds fr the water to reach the end of the pole.
-Philip