How to Install a Camper Van Water System Using PEX-A Uponor Fittings

Installing a camper van water system may seem overwhelming, but with the right tools and a step-by-step approach, you can build a reliable system that includes cold and hot water, an integrated gray tank, and a shower/washdown hose—all in a tight space. In this guide, we'll walk you through the water system install using PEX-A (Uponor) fittings in a 2020 Ford Transit Mid Roof van.

Why Choose PEX-A for Your Van Build?

PEX-A (also known as Uponor PEX) is a flexible plumbing system that's ideal for small, tight spaces like camper vans. It's highly durable, easy to work with, and provides reliable leak-free seals using an expansion fitting system. While the toolset can be expensive upfront, the long-term reliability and ease of use make it well worth the investment for serious van builders.

Key Components of This Build

Here's a high-level overview of the main water system components used in this installation:

Component	Description
Freshwater Tank	20-gallon over-the-wheel-well tank with dedicated intake, overflow, and breather ports
Water Pump	SeaFlo 55 PSI 12V pump with inline strainer and self-priming up to 6 ft
Hot Water Heater	AO Smith 2.5-gallon, 120V, point-of-use water heater
Sink	Elkay granite composite sink with custom gray water tank
PEX-A System	Flexible plumbing layout using Uponor expansion fittings
Gray Water Tank	7-gallon Panther RV tank with easy-access top and clean-out
Shower Kit	Rear outdoor washdown shower with control valve (covered in a separate video)

Layout & Planning

One of the biggest challenges in van builds is optimizing limited space. This van had additional constraints due to a relocated rear AC unit. Every inch had to be carefully planned. The AC unit was relocated under the sink and vented using insulated 4″ ducting.

A Rev-A-Shelf pull-out drawer was installed next to the plumbing to maximize kitchen storage. Custom cutouts and measurements were taken to fit all plumbing, electrical, and mechanical components seamlessly.

Cold and Hot Water Line Routing

• Cold Line: Starts at the bottom port of the freshwater tank, goes through a drain tee with shut-off, then into the pump's strainer and the SeaFlo pump. From there, it splits off to the sink, shower, and hot water tank.
• Hot Line: Heated water exits the AO Smith tank and tees off to serve the sink and shower.
• All PEX lines are secured with plastic-specific clamps to prevent wear from vibration.

Overflow & Pressure Relief System

• Overflow Vents: Designed to drain beneath the van. This is helpful when you can't visually see the water level.
• Hot Water Tank Pressure Relief: A safety valve routes excess pressure to the ground to prevent flooding in the van in case of failure.

Installing PEX-A Fittings: Tools & Tips

Tools Needed:

• PEX-A Expansion Tool (e.g., Milwaukee M12/M18) – ~$400 investment
• PEX Pipe Cutter – Clean 90° cuts are essential
• Expansion Sleeves & Brass Fittings – Use brass for durability in mobile builds

Installation Tips:

• Always plan your expansion sequence before activating the tool—once expanded, the pipe begins to contract quickly.
• Expand the sleeve 6–10 times depending on ambient temperature and material stiffness.
• Push fittings in within 2–3 seconds after expanding to ensure a solid seal.
• Use plastic pipe clamps and avoid metal to prevent wear from road vibration.

Drainage & Winterization

• Drain valve is built-in, allowing easy winterization or draining after a trip.
• Check valve installed on overflow to prevent backflow into the tank.
• NSF-rated thread sealant is used for all fittings, even on the gray water system, for maximum safety and reliability.

Final Thoughts on the Water System

This PEX-A system offers flexibility, durability, and peace of mind in a compact camper van space. By using thoughtful design, proper tools, and smart routing, you can build a high-functioning water system with hot and cold water, integrated drainage, and maintenance access. This approach is perfect for DIYers who want a clean, professional result in their van conversion.

Recommended Products

Product	Purpose	Notes
Milwaukee PEX Expansion Tool	Expanding PEX-A tubing	Required for installation
SeaFlo 12V Water Pump	Pressurizing water system	Self-priming up to 6 ft
AO Smith 2.5 Gal Water Heater	Hot water supply	120V, heats quickly while driving
Panther RV Gray Water Tank	Gray water collection	Easy clean-out and food-safe
Elkay Sink	Compact kitchen sink	Granite composite, durable
PEX-A Brass Fittings	All water connections	Stronger than plastic alternatives

Have Questions?

Let us know in the comments if you have any questions about building your camper van water system or working with PEX-A. Stay tuned for future videos on installing a faucet, shower system, and electrical connections.