Lesson 5.2: Plumbing

So, you want a sink, shower, toilet, or maybe a full wash station inside your container? Whether you're building an off-grid cabin, mobile washroom, jobsite office, or tiny home, adding plumbing to a shipping container isn’t just possible, it’s practical.

But unlike a traditional house, plumbing inside a container comes with its own set of challenges. You’re working with a steel shell, limited under-floor access, and potentially remote locations without municipal water or sewer lines.

This lesson will walk you through how to plan, install, and protect plumbing systems inside your shipping container build.

What Plumbing Can You Add?

With the right planning, you can install:

Showers and bathtubs
Toilets (flushing or composting)
Sinks (kitchen, laundry, or utility)
Hot water heaters (tank or tankless)
Greywater holding tanks or blackwater septic systems

The key is understanding your supply and drainage system, and making sure everything’s sloped, vented, and sealed properly.

Step 1: Planning Your Water System

Before installing anything, answer these:

Water Source:

City water?
Well?
Rainwater catchment?
Gravity-fed tank?
Off-grid with pump system?

Water Heater:

Electric? Propane? On-demand?
Inside or mounted outside?

Wastewater Disposal:

Municipal sewer?
Septic tank?
Holding tank?
Compost toilet?

Climate Considerations:

Will this container operate in freezing temps?
Is everything inside, or are some components outdoors?

In cold climates, you’ll need heat trace, insulation, and proper venting to prevent frozen lines.

Step 2: Roughing in the Plumbing

Floor Penetrations:

Mark all pipe exits BEFORE you insulate or floor your container.
Use a hole saw and grommet seals to protect pipes passing through steel.

CMW Tip: We recommend framing your floor platform to allow pipe clearance above the steel container floor, especially when the container will sit on a pad or blocks.

Drainage (DWV):

Use ABS or PVC piping for drainage.
Maintain proper slope (1/4” per foot) toward the outlet.
Install cleanouts and P-traps per plumbing code.
Ensure you have roof venting or an air admittance valve (AAV).

Supply Lines:

Use PEX or copper depending on local code.
Plan shutoff valves, hose bibbs, and pressure relief valves.

Bonus: Use a manifold system for flexible routing and fewer fittings.

Step 3: Fixtures and Finishings

You can use standard residential sinks, toilets, and showers, or compact marine and RV-style fixtures to save space.

Common modifications:

Wall-mounted faucets on metal walls
Tankless water heaters mounted to interior walls or cabinets
Under-counter tanks for greywater collection

Don’t Forget These Critical Components

Drain Vents – Required for every fixture to prevent vacuum lock
Water Heater Clearance – Follow all ventilation and safety guidelines
Roof Vents – Cut and flash properly to avoid leaks (CMW offers roof flashing kits!)
Access Panels – Make traps, cleanouts, and valves accessible