Plumbing Systems

Transit Van Plumbing: Water Systems Built for the Ford Body

Running water turns a van into a home. The Transit's narrower body creates some unique plumbing considerations — here's how we handle them.

Plumbing in a Ford Transit conversion works the same way as any van build at the component level: fresh water tank, 12V pump, PEX supply lines, a sink, possibly a shower, gray water collection, and a drain system. The Transit-specific part is fitting all of that into a body that's about 68 inches wide at floor level — narrower than both the ProMaster and the Sprinter.

That doesn't mean plumbing is harder in a Transit. It means the design work matters more. Tank shapes, supply line routing, shower dimensions, and gray water plumbing all need to account for the available space. We've done enough Transit builds to know what works and what compromises are worth making.

Fresh Water Tank Placement

The fresh water tank is the largest single plumbing component and usually the hardest to place. In a Transit, you have three main options:

Under the Van (Exterior Mount)

Mounting the tank on the underside of the van frees up interior space completely. This is the most common approach for 20+ gallon tanks. The tank is protected by the frame rails and sits between the axles.

Transit-specific consideration: AWD models have the driveshaft tunnel running centrally underneath, which limits where you can mount a wide tank. You may need a narrower, longer tank shape — or two smaller tanks side by side. 2WD models have more clearance underneath.

Cold weather note: Exterior tanks are exposed to freezing temps. For four-season use, we insulate the tank and sometimes add a heat pad. For three-season California use (most of our builds), external mounting works fine.

Under the Bed Platform

If the electrical system doesn't take up the entire under-bed area, water tanks can share that space. This keeps them inside the insulated shell of the van (better for cold weather) and accessible for maintenance.

Transit-specific consideration: The Transit's narrower width means under-bed space is tighter. In builds with a large battery bank, you may need to choose between under-bed tanks and under-bed batteries. We work this out during the design phase so nothing conflicts.

In a Cabinet or Garage Area

Smaller tanks (10–15 gallons) can mount inside a lower cabinet or in the rear garage area. This is the simplest install but uses valuable storage space. Best for basic builds where water needs are modest.

Build Tier	Fresh Water	Gray Water
Basic	10–20 gallons	10–15 gallons
Standard	20–30 gallons	15–25 gallons
Premium	30–40 gallons	25–35 gallons

Hot Water Options

Hot water is what separates a basic build from one that feels like home. In a Transit, space efficiency matters more than in wider vans, so the water heater choice affects your layout:

Truma Combi (Most Popular)

The Truma Combi handles both space heating and hot water in a single unit. It's the go-to for Transit builds because you get two systems in one footprint. It runs on propane or diesel (depending on the model), heats 2.6 gallons of water at a time, and keeps the cabin warm in cold weather.

In a Transit, the Truma typically mounts under a bench seat or in a lower cabinet. Its compact size makes it a natural fit for the narrower body.

Tankless Water Heaters

Standalone tankless units (Girard, Camplux) heat water on demand — no stored tank to keep warm. They're good for builds that already have a separate diesel heater for cabin heat. They mount on a wall or inside a cabinet and take up minimal space.

The trade-off: they require propane, adequate ventilation, and consistent water pressure to function properly. In very cold conditions, startup can be slow.

No Hot Water (Basic Builds)

Plenty of basic builds skip hot water entirely. Cold water at the sink covers cooking, dishes, and hand washing. If you're primarily a warm-weather traveler or weekend warrior, hot water is nice but not essential. You can always add it later if you change your mind.

Shower Setups in a Transit

This is where the Transit's width matters most. At 68 inches between the walls, you're working with less room than a ProMaster (which is about 75 inches). A shower is absolutely doable, but the design needs to be intentional.

Wet Bath (Combined Shower/Toilet Room)

The most space-efficient option. A small enclosed room — typically 24" to 30" wide — serves as both the shower and the toilet area. The entire room is waterproofed, with a drain in the floor. After showering, the space doubles as your bathroom.

In a Transit, a wet bath usually sits across from the kitchen or behind the cab area. It takes up about 2 to 3 feet of van length. Most of our Standard and Premium Transit builds include a wet bath because it gives you a daily shower without dominating the layout.

Dedicated Shower Stall

A separate shower stall (distinct from the toilet area) is possible in longer wheelbase Transits. It requires more floor space but gives you a more comfortable shower experience. This is typically a Premium build feature in a Transit because of the layout space it requires.

Outdoor Shower

A hot/cold outdoor shower mounted on the exterior — usually near the rear doors or the side slider. Simple to install, takes up zero interior space, and works great in warm climates. Many builds include this as an addition to an indoor shower, not a replacement.

For Southern California use, an outdoor shower covers 90% of your showering. For four-season travel, you'll want an indoor option too.

Shower Drain and Gray Water

Shower water drains to your gray water tank through a floor drain. In a Transit, the drain routing needs to work with the narrower floor space and (in AWD models) the driveshaft tunnel underneath. We use a combination of gravity drainage and a small sump pump where needed to move water from the shower pan to the gray tank reliably.

Gray Water System in the Transit

Gray water is everything that goes down a drain — sink water, shower water. It collects in a tank and gets dumped at an RV dump station or approved drain. The gray water system is straightforward, but the Transit body creates a few routing specifics:

Tank Location

Gray water tanks almost always mount on the underside of the van. They sit below the floor drains (gravity is your friend) and have a dump valve accessible from outside. In a Transit, the tank mounts between the frame rails, similar to the fresh water tank.

On AWD models, the same driveshaft tunnel that affects fresh water tank placement also affects the gray tank. The solution is the same: narrower tank shapes or split tanks positioned on either side of the tunnel.

Drain Line Routing

Drain lines from the sink and shower need to run through the floor to the gray tank below. In a Transit, we route these through the floor insulation and sub-floor, keeping them inside the heated envelope as much as possible to prevent freezing.

The key is maintaining proper slope — water needs gravity to reach the tank. In some layouts where the drain point is far from the tank, we install a small sump pump to move water reliably. This is more common in Transit builds than Sprinter builds because the narrower body sometimes limits where the sink and shower can go relative to the tank.

Winterization

For builds that will see freezing temperatures, we protect the plumbing system in several ways:

•PEX tubing: We use PEX for all supply lines. It has some freeze tolerance — it can expand slightly without bursting, unlike rigid pipe. It's not freeze-proof, but it's far more forgiving.
•Interior routing: Supply lines are routed through the insulated interior wherever possible, keeping them in the heated space.
•Tank insulation: Exterior tanks get foam insulation wraps. For extended cold-weather use, we can add thermostatically controlled heat pads.
•Drain-down capability: Every plumbing system we build includes the ability to drain all water from the lines and tanks when winterizing for storage or extreme cold.

Transit Plumbing Cost by Tier

Plumbing is one of the more affordable systems in a conversion, but it scales quickly once you add hot water and a shower:

Basic ($1,500–$3,000)

Cold water only. Fresh water tank (10–20 gallons), 12V pump, PEX supply lines, single sink, gray water tank, basic drain system. Gets the job done for cooking, cleaning, and hand washing.

Standard ($3,000–$5,000)

Hot and cold water. Larger fresh tank (20–30 gallons), Truma Combi or tankless water heater, indoor shower with waterproofed wet bath, composting toilet, properly sloped gray water system. This is what most full-time builds need.

Premium ($5,000–$8,000)

Everything in Standard, plus larger tanks (30–40 gallons fresh), water filtration system, outdoor shower, winterization features (insulated tanks, heat pads), and premium fixtures. Built for daily use in any climate.

For a full cost breakdown of all systems, see our Transit conversion cost guide.

Toilet Options

Toilets aren't technically part of the plumbing system (most van toilets don't connect to the water supply), but they go hand-in-hand with your bathroom layout:

•Composting toilet (Nature's Head, Cuddy): Self-contained, no black tank needed, minimal odor when maintained properly. The most popular choice for van builds. Works well in the Transit's compact wet bath.
•Cassette toilet: Simpler and cheaper. Has a removable waste cassette that you dump at an RV dump station. Needs more frequent emptying than a composting toilet but takes up less space.
•Portable toilet: The budget option. A standalone unit that you can stow when not in use. No installation required.

In a Transit, the toilet typically lives in the wet bath. Composting toilets need ventilation (a small fan and exterior vent), which we factor into the wall or floor plan during design.

Frequently Asked Questions

How many gallons of fresh water can a Ford Transit hold?

Most Transit builds carry 15 to 30 gallons of fresh water. A 15-gallon tank handles weekend trips and light daily use. For full-time living or traveling with a partner, 25 to 30 gallons gives you more range between fill-ups. The Transit's narrower body means tank selection is more critical than in a wider van like the ProMaster.

Can you have a shower in a Ford Transit?

Absolutely. We build indoor showers in Transit conversions regularly. The narrower body means the shower stall or wet bath needs to be designed efficiently, but it's completely doable. Most builds use a 24" to 28" wide shower area — tight by house standards, but functional for daily use. Outdoor showers are also an option for a simpler setup.

Does the Transit's width affect plumbing?

Yes. The Transit is about 68 inches wide at floor level, which is narrower than a ProMaster. That affects where tanks mount, how the shower is sized, and where supply lines run. It doesn't make plumbing impossible — it just requires more deliberate design work to make everything fit without compromising livability.

What type of water heater works best in a Transit?

The Truma Combi is the most popular choice because it handles both space heating and hot water in one compact unit — important when space is limited. Standalone tankless water heaters (like the Girard or Camplux) work too if you already have a separate diesel heater for climate control. We size the water heater based on your shower and hot water usage.

How much does Transit van plumbing cost?

Basic plumbing (cold water only, simple sink, hand or electric pump) runs $1,500 to $3,000. Standard builds with hot water and a shower run $3,000 to $5,000. Premium builds with larger tanks, water filtration, outdoor shower, and winterization features range from $5,000 to $8,000. These include materials and labor.

Plan Your Transit Water System

Tell us how you'll use water on the road — daily showers, simple sink setup, or full bathroom — and we'll design a plumbing system that fits the Transit body and your lifestyle.

Tell Us About Your Build