Valterra ABS Fresh-Water Tanks: 15 & 18 Gallons, Fill Kit Parts

Valterra's R8030 and R8036 are rectangular black ABS fresh-water tanks for gravity-fill, low-pressure use. They share a 16-by-8-inch cross section, but the 15-gallon version is 30 inches long and the 18-gallon version is 36 inches long. The matching RK907 kit provides a 90-degree fill elbow and installation fittings. This reference helps you compare the tank sizes and identify which components belong to the tank versus the separate fitting kit.

Compare the tanks and fill kit

Both tanks are one-piece extruded ABS with internal baffles spaced at 18-inch intervals to help control water movement. Each comes with six ⅜-inch threaded fitting inserts—three at each end. They do not include the RK907 fill kit or a mounting bracket system. The manufacturer specifies low-pressure gravity fill/drain only and says these tanks are not for use with electric pumps; confirm the suitability of your exact RV plumbing design before selecting either tank.

Identify the tanks and actual products

R8030 — 15-gallon ABS fresh-water tank

The shorter black ABS tank measures 30 × 16 × 8 inches. It has internal surge-control baffles and six 3/8-inch threaded fitting inserts, with three located at each end. Designed for gravity-fill and low-pressure drain applications.

View R8030

R8036 — 18-gallon ABS fresh-water tank

The longer 18-gallon model has the same 16 × 8-inch cross section as R8030 but extends to 36 inches. It also has six 3/8-inch threaded inserts and internal baffles. Valterra identifies this model as discontinued; check availability before selecting it.

View R8036

RK907 — 90° barbed tank-fill fitting kit

A fitting kit for a compatible ABS tank installation: 1¼-inch 90° barbed fill elbow, two ⅜-inch female pipe-thread drain nuts, one ⅜-inch male pipe-thread plug and ¼ pint of solvent cement. The tank is sold separately.

View RK907

RK907 fitting kit: component reference

The table identifies the components Valterra lists for the RK907 tank-fill kit. Numbers 1–4 are labels used in this guide, not manufacturer exploded-diagram callout numbers. These are separate parts from the tank's existing ⅜-inch inserts.

How the gravity-fill connections relate

This is a simplified parts-location overview for identifying the connections, not a drill-position drawing or a vehicle-specific plumbing schematic. The fill, drain and vent positions depend on the planned installation and the manufacturer-approved fittings.

Before choosing or installing a tank

1. Measure the available compartment. Allow for the full 30- or 36-inch tank length, its 16-by-8-inch cross section, secure support, pipe connections and service clearance.
2. Confirm the water-system design. Valterra specifies gravity-fill, low-pressure use only and expressly excludes use with electric pumps. Do not assume these ABS tanks can replace a pressurized or pump-fed tank merely because the capacity fits.
3. Identify every connection. The tanks include ⅜-inch threaded inserts at the ends; the RK907 1¼-inch barbed fill elbow is a separate solvent-weld fitting. Match the planned fill, vent and drain arrangements before cutting or bonding.
4. Use the correct bonding procedure. Verify tank material, hole location and the fitting's intended placement. Follow Valterra's fitting and solvent-cement instructions; do not guess a cutout dimension.
5. Provide tank support and a clear vent path. Water adds substantial weight, so account for full-tank load, travel movement and secure mounting. Check for leaks before returning the RV to service.

Related fresh-water parts

For the exterior gravity-fill opening, use our Valterra gravity and city-water hatch guide. For freshwater hose connections, see our drinking-water hose comparison. These references cover different components and do not change the low-pressure restriction for these tanks.