The pump and shower head design is based on a low volume pump, I think it only pumps 11 litres per minute, but that is plenty for a shower.
This is my prototype, consisting of your bog standard shower head hooked up to a Jabsco pump with an irrigation pre-filter. I had to make sure that the pump would start pumping from a dry start with a head of 500mm.
It's pretty hard to photograph a shower! Everything is long and thin...
I built a stainless steel box to cover the pump, to keep it dry and to reduce the noise somewhat. The top is TIG welded, but the bottom is open so there is plenty of airflow around the pump.
A simple perforated stainless 'cage' on top of the pump cover holds some shampoo and soap.
At the bottom, you can see the little filter to stop hair and sand being 'recycled' through the system.
The pickup for the water is roughly in the middle of the shower base.
Just your standard Bunnings shower head, on some 15mm black poly pipe.
The shower head is fixed to the ceiling with a custom made HDPE block, so that the head can still be tilted and swivelled, but it can't move away from the ceiling even over corrugations.
I just heat welded the HDPE block to a piece of HDPE sheet and riveted it to the roof. Simple but strong.
The final job is to connect up the shower base to the waste pipe from under the truck. I made a start today, but turns out the fittings I bought were inch and a quarter, not inch and a half, so that'll be tomorrow's effort.