I use similar clips under the van to hold the filter up out the way and out of sight when I am hooked up to water.
For storage, I have made up some clip on ends. They look like what you might fit on the end of a hose, except on the hose end of the fitting it is threaded and I screwed in the appropriate plug. 3/4 bsp I think.
You just push them on the ends of the inline water filter. The filter cannot leak any water, so you can just throw it in the boot, in a tub, or clip it on the boot wall etc with no fear of any water dripping anywhere.
I have been using the end caps for many years with never a drop leaked.
