Home made PVC water tank for washing or shower?

I am thinking about installing a home made pvc pipe water tank on my teardrop roof rack for shower or dish washing. It would be a 6 inch pipe (maybe 2 manifolded together) capped on both sides about 5 feet long. Garden hose fitting tapped on the top for filling. Garden hose tapped on the bottom for using water. Gravity from the elevated tank would provide a trickle of water. Maybe I could also compressed air tap it on the top for attaching an air pressure hose from my vehicle on board air system when I want good water pressure... Like a super soaker water gun....
HEY! My teardrop would be a super soaker water canon at teardrop gatherings!
It should get good solar gain for water heating.
Anybody done this before? Have a plan or sketch?

HEY! My teardrop would be a super soaker water canon at teardrop gatherings!

It should get good solar gain for water heating.
Anybody done this before? Have a plan or sketch?