Heard from AV last month that they should be able to get our truck in the workshop and build our box Oct-Dec. In the meantime, we've been planning out our plumbing.
This is the part-time-recirculating shower part of it:
View attachment 731444
The idea is for all the soap and grime to go away into the grey tank (~10L per shower) like with any normal shower, but then the remaining "luxury" part of the shower (if we want it) that's mostly clean water can be recirculated through some filters, a semi-clean tank, then a heat exchanger to top up the temperature, so we can stand under the hot shower for as long as we want without wasting additional water.
Then this semi-clean water can be re-used once later on for stuff like washing the dog, rinsing muddy boots, soaking dirty dishes, etc. Whatever we don't need to waste extensively filtered super clean water on. The semi-clean water can also be recirculated internally through the heat exchanger if we want to heat up those 20L.
We haven't seen it done quite like this before, but we're planning to order the main components soon to do some testing before finalizing for the truck.