Decide How Much Water You Actually Need
Tank size affects weight and space. Estimate daily drinking, cooking, handwashing and shower use, then compare that with how often you can refill. Remember that one US gallon of water weighs about 8.34 pounds.
Keep Heavy Tanks Low and Secure
Fresh and gray water tanks need strong restraints that account for vehicle movement. Their location also affects weight distribution and freezing risk.
Plan the Pump and Service Components Together
The pump, filter, accumulator if used, shutoff valves and drain points should be accessible. A compact installation is not useful if a small leak requires removing permanent cabinetry.
Drainage Needs Slope and Venting Strategy
Gray-water plumbing must drain reliably when the vehicle is not perfectly level. Avoid unnecessary traps and long flat runs where practical, and follow the requirements for the fixtures and tanks you install.
Design for Winterization and Sanitizing
If the van will see freezing temperatures, plan a way to drain vulnerable components. The fresh-water system should also be easy to sanitize periodically.
Pressure-Test Before Closing Walls
Fill and test the system while every fitting is visible. Check under pressure, inspect drains, cycle the pump and repeat the inspection after a short drive because vibration can reveal issues that do not appear while parked.
Turn the research into a build plan
The free guides on this site explain individual decisions. The Van Conversion Manual is designed to keep the major systems organized in one complete digital reference for the project.