In this pretty long but very informative video i show you water system i made in my sprinter van conversion. It includes 150L water tank, pump, water accumulator, AC 10L water heater, pressure meter and toilet flushing electric valve. A lot of thing to watch!
List of some items i use:
Shurflo ProBlaster - https://amzn.to/2k7rhky (i broke it, but this pump is best)
Shurflo Aqua King - https://amzn.to/2GBqgdy (my second pump. good too, but first is little better)
Water heater (not as mine but very similar) - https://amzn.to/2LgijOb
Shower Thermometer - http://s.click.aliexpress.com/e/EAyz7uN