Water is one of those camper van systems that looks simple until you actually start designing it. At first glance, it seems like all you need is a tank, a pump, a sink, and a drain. But once the van needs to support four-season travel, daily showers, safe drinking water, and cold-weather use, the system becomes much more important.

A poor water system usually fails in predictable ways. A hidden fitting leaks behind cabinetry. A pump chatters loudly every time the tap opens. The gray tank freezes. The dump valve becomes a block of ice. A filter clogs because it is difficult to service. Or the entire system has to be torn apart just to winterize it.

The goal of this design is not to make the most complicated system possible. The goal is to make a system that is comfortable, reliable, serviceable, and appropriate for a true four-season Canadian van build.

The system is built around one simple rule: fresh water stays inside; gray water gets actively protected outside.

This is not a black-tank system. Because the build uses a Dry Flush toilet, the toilet does not connect to the fresh water system, gray water system, or any dedicated black tank.

A camper van water system is normally pressurized by one central pump. There is no separate pump at each faucet. When a tap opens, pressure drops and the pump turns on. When the tap closes, pressure rises and the pump shuts off.

For this kind of build, a proven 12V diaphragm pump such as the SHURflo Revolution 4008 is a sensible choice. It is common in RV and marine applications, parts are easy to find, and it provides enough flow for a sink and shower without being excessive.

The filtration strategy needs to solve two different problems.

First: normal everyday water from city supplies, campgrounds, friends’ houses, and RV fill stations should taste good and be safe to use.

Second: the van should have a way to make questionable or natural-source water safe when travelling remotely.

Those are related goals, but they do not need to be solved by forcing every drop through an overly complicated permanent system.

Reverse osmosis is common in houses, but it is usually not the best fit for a camper van. RO systems waste water, fill slowly, require additional storage, and add complexity. In a vehicle where every litre matters, wasting water to make water is a poor tradeoff.

A better van strategy is sediment filtration + carbon filtration + UV purification. UV does not remove sediment or improve taste, which is why it should not be used alone. But after sediment and carbon filtration, UV adds an excellent final safety layer for drinking water.

This build already uses a Rixen hydronic heating system. That means domestic hot water can be produced through the hydronic system rather than adding a separate propane, diesel, or electric water heater.

The Rixen system heats coolant. That heat is transferred to domestic water through a heat exchanger. A thermostatic mixing valve then blends hot and cold water down to a safe and usable outlet temperature.

This approach fits the overall build philosophy: one integrated heating platform for cabin heat, floor heat, engine preheat, and domestic hot water.

The fresh water tank is relatively easy because it lives inside the heated van. The gray tank is harder because it typically lives underneath the van, outside the heated envelope, exposed to wind, road spray, and deep cold.

For occasional shoulder-season camping, a simple tank heater pad may be enough. For Saskatchewan winter operation down to -30°C or -35°C, it is not enough to treat the gray tank as an afterthought.

The gray tank should be surrounded by a purpose-built insulated enclosure. The purpose of the box is not simply to make the tank look tidy. It is there to reduce heat loss, protect the tank from road exposure, and make the heating pad effective in deep cold.

A practical enclosure would use rigid foam insulation around the tank, sealed seams, drainage considerations, and a protective lower skin or skid plate. The goal is to create a small controlled environment around the tank rather than letting the heating pad fight open winter air.

Even a four-season van needs a winterization strategy. The system may be heated while in use, but there will still be times when the van is stored, serviced, or allowed to cool down.

The system should be designed from the beginning with low-point drains, bypass valves, and a way to blow out the lines with compressed air. These small decisions can turn winterization from a frustrating afternoon into a simple maintenance routine.

The exact brands and dimensions will depend on final layout, tank location, cabinet design, and drain routing. This list is intended as a design-level bill of materials for a premium DIY water system.

1. Finalize tank locations before building cabinetry or underbody mounts.
2. Map every fixture including sink, shower, fill port, pump, filters, and Rixen hot water components.
3. Design service access around the pump, filters, valves, and manifolds.
4. Install the fresh tank and fill/vent lines.
5. Mount pump, accumulator, and filters in one accessible service bay.
6. Run hot and cold PEX using crimped fittings and proper supports.
7. Install sink and shower plumbing.
8. Install gray tank, heater pad, heat trace, insulation, and enclosure.
9. Pressure test the system before enclosing walls or cabinetry.
10. Sanitize and commission the system before travel use.

A camper van water system is not just a collection of plumbing parts. It is an integrated comfort and survival system. In a fair-weather van, a basic tank and pump might be enough. In a four-season Canadian build, the system needs to be designed with freezing, serviceability, filtration, hot water, and real-world maintenance in mind.

The most important design decision is simple: keep fresh water inside and protect gray water properly outside.

That means an interior fresh tank, a proven pump, crimped potable PEX, accessible filters, Rixen-supplied hot water, a real shower, a Dry Flush toilet that stays out of the plumbing system entirely, and an underbody gray tank that is heated, insulated, monitored, and serviceable.

Done properly, the result is a water system that supports everyday comfort without becoming fragile or overcomplicated. It is simple enough to maintain, robust enough for remote travel, and thoughtfully designed for the reality of Canadian winter.