How to Install a Sprinter Undercarriage Water Tank: Passenger-Side

Last updated: September 15, 2026

Overview

Install a Sprinter 11-gallon undercarriage water tank on the passenger side in ~2 hours using 3/8" rivnuts, bolts, and mounting straps. The tank mounts under the slider door step, between the frame and step cutout. Dry-fit the tank, mark factory holes for your mounting straps, drill and clean holes, install rivnuts, prime exposed metal, and bolt the tank in place with Loctite on all fasteners. Your Sprinter gains water storage without interior space loss.

Before You Start

Vehicle: Mercedes Sprinter
- Gas engine Sprinters: the exhaust runs closer to the frame on gas models. Install a heat shield (not included) between the tank and exhaust before use.

Kit: GoCode 11-Gallon Undercarriage Water Tank (SP-UC-11)
Mounting location: Passenger side, under the slider door step, between the frame and the step cutout
Estimated installation time: ~2 hours

Tools & Materials

Drill with an 1/8" bit and a stepped bit
Center punch (optional)
Marker
Rust inhibitor or primer (for any exposed bare metal)
Rivnut installation tool (required, not included)
Ratchet w/ 9/16” socket

Mounting straps, 3/8" rivnuts, 3/8" bolts, and Loctite for the mounting bolts (all included with tank order)

Installation Instructions

1. Locate the frame rail mounting points
Start at the muffler bolt on the frame rail. Remove it with a 1/2" socket and set it aside. You'll reuse this bolt to mount the first bracket. From that hole, measure toward the rear of the van and mark the hexagon shaped holes at 12 3/4" and 22 1/8".

2. Mark the side wall
Hold a bracket straddled between the frame rail and the side wall, aligned with the muffler bolt hole and perpendicular to the rail. Mark the side wall at the bracket's mounting point. Using that first mark as your control point, measure and mark at 12 3/4" and 22 1/8".

3. Drill the mounting points
Drill every marked hole out to 17/32". A step bit works well here, or run a series of increasingly larger bits. Leave the muffler bolt hole alone. That one is reused as is.

4. Clean up the shavings
Take a minute to sweep out the metal shavings before you keep going. Rolling around on them is no fun.

5. Prime and set the riv-nuts
Prime the exposed metal at each hole, then install the riv-nuts. We use a pneumatic riv-nut gun, but any riv-nut tool will do the job.

6. Mount the tank
Lift the tank into place and start the provided 3/8" bolts through the brackets and into the riv-nuts. Use Loctite on every bolt, and don't tighten anything until all of them are started. Once they're all threaded, tighten them with a 9/16" socket. The tank is mounted and you're ready to plumb.

Installation Video