Bear in mind a shower in a van is a whole lot more of a PITA than a shower in a house.
1) Needs a calorifier fitted to the engine/exhaust ££££. Also means you only have hot water on days you drive somewhere, and a few hours after you stop (i.e. useless for all day epics, any trip that involves parking for more than da day and 24h races).
2) Need’s pumps, these respond to drops in pressure and switch on to maintain it. If the system springs a leak it will keep pumping/leaking untill the tanks is dry and all that water will end up inside the van (they never seem to leak somewhere convenient like under the van).
3) Tanks, you’ll need enough water to wash you and any mates, and enough tanks again to store it. You then have to pay somewhere to empty the tank unless you can dicreetly park next to a drain (dumping a load of soapy water into a river isn’t exactly environmentaly friendly).
It’s a lot of money/hastle to avoid paying 50p to use the chaning rooms at a trail center with half decent showers, or jumping into a cold lake on a ‘camping’ trip. If I was planning a van, showers and toilets would be the very bottom of the list,