6 Best Compact Grey Water Tanks For Van Conversions

Managing waste in a van conversion is rarely the most glamorous part of the build, but it is undeniably the most critical for maintaining a livable interior. Choosing the wrong grey water tank can lead to leaks, space-robbing bulk, or, worst of all, a lingering smell that ruins the entire travel experience. The following selection balances durability, dimensions, and practical installation to help you find the right fit for your rig.

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Class A Customs 10 Gallon: Best Overall Pick

The Class A Customs 10-gallon tank hits the sweet spot for most weekend warriors and part-time van dwellers. Its rectangular shape is highly versatile, allowing it to fit neatly under a sink cabinet or tucked away in a rear garage area without sacrificing excessive floor space. Because it is manufactured with high-density polyethylene, it offers a robust, puncture-resistant shell that stands up to the vibrations of the open road.

For those who do not want to sacrifice an entire corner of their floor plan, this unit offers enough capacity for several days of modest water usage. It is the gold standard for builds where simplicity and reliability take precedence over high-tech plumbing solutions. If you need a tank that just works without requiring custom fabrication or complex mounting, this is the definitive choice.

RecPro 15 Gallon Wheel Well: Best for Saving Space

Space is the most expensive commodity in a van, and the area directly over the wheel well is often wasted. This RecPro tank is specifically molded to hug the contours of a wheel arch, turning a dead zone into a functional storage solution. It maximizes volume while keeping the center of gravity low and tucked toward the sidewalls.

The 15-gallon capacity is generous for solo travelers or pairs who prioritize longer stretches between dump stations. While it requires a bit more planning to secure properly against the metal sidewall, the footprint efficiency is unmatched. This tank is for the builder who views every square inch of the van as a premium asset.

Barker 15 Gallon Tote-Along: Best Portable Tank

Not every build requires a permanent, plumbed-in grey water system, especially for those operating out of simpler, non-van-life-specific vehicles. The Barker Tote-Along functions like a piece of luggage, featuring wheels and a handle that make trips to the dump station effortless. It removes the stress of needing to park your entire van perfectly over a drain.

This is the ideal solution for anyone who finds the idea of permanent, hard-plumbed tanks too intimidating or too difficult to integrate into their layout. It is rugged enough to handle heavy use and provides a modular alternative that can be tucked away when not in use. If you value flexibility and want to avoid the complexities of internal plumbing, this portable option is the superior path.

Valterra R8012 12 Gallon: Best Budget Option

The Valterra R8012 is a classic in the industry for a reason: it is affordable, widely available, and intentionally simple. It features a straightforward, low-profile design that is easy to plumb for basic gravity-fed drainage. For those keeping a close eye on their build budget without wanting to cut corners on safety, this is a dependable workhorse.

While it lacks the fancy mounting hardware of more expensive units, its standard dimensions make it compatible with common van cabinet sizes. It is perfectly suited for a DIY builder who plans to construct a simple wooden cradle or strap-down system for support. Choose this if you prefer to allocate your budget toward high-quality appliances rather than expensive plumbing infrastructure.

Ronco B390 7 Gallon: Best for Super-Tight Builds

In a micro-van or a minimalist setup, finding space for a large tank is often impossible. The Ronco B390 is compact enough to slide into very narrow vertical voids or under tight cabinetry where other tanks simply won’t fit. Its 7-gallon capacity is intentionally small, serving the needs of those who prioritize light weight and high turnover of water.

This tank acknowledges the reality that smaller capacity means more frequent dumping, which is often a worthwhile tradeoff for a more open interior. It is built to the same high standards as larger models but scaled down for the minimalist. If you are building a “stealth” rig where interior space is the absolute priority, this is your primary contender.

RecPro 5 Gallon Tank: Best for Minimalist Vans

The 5-gallon RecPro tank represents the absolute baseline for a functional sink setup. It is small, lightweight, and incredibly easy to handle even when full, making it ideal for those who prefer to dump their grey water daily. The design is so compact that it can often be stowed inside a single kitchen drawer or behind a small vanity cabinet.

This unit is perfect for solo travelers who rarely cook in the van and primarily use water for basic hand washing and brushing teeth. It eliminates the problem of stagnant grey water buildup and the associated odors. It is the perfect choice for the ultra-minimalist who wants the convenience of a sink without the plumbing footprint of a bathroom.

How Big a Grey Water Tank Do You Really Need?

Selecting tank size is a balancing act between physical space and the frequency of trips to a dump station. A common rule of thumb is to match your grey water tank size to your fresh water tank size, but many van dwellers choose to downsize the grey tank to save space. If you are mindful of your water usage—using a spray bottle or a low-flow faucet—you will find that you rarely fill a 10-gallon tank in a single day.

Overestimating your needs leads to excessive weight and wasted storage space. Conversely, choosing a tank that is too small results in daily chores that quickly become tiresome. Evaluate your lifestyle: if you are frequently camping in developed areas with easy access to drains, a smaller tank is perfectly fine. If you are embarking on long, off-grid excursions, you need to prioritize maximum capacity.

Mounting Your Tank: Inside vs. Undermount

Mounting a tank inside the van—usually under the sink—is the most common approach for ease of installation and protection from freezing temperatures. It requires a dedicated cabinet and a vent line to prevent odors from entering the living area. This is the safest bet for anyone who plans to travel in colder climates, as internal heat keeps the water from turning into a block of ice.

Undermounting, where the tank sits beneath the chassis, keeps the interior of the van entirely clear of plumbing and tanks. However, this exposes your system to road debris, freezing weather, and the difficulty of finding ground clearance. Only choose an undermount if you are confident in your ability to install robust, insulated hardware that can withstand the harsh reality of being attached to the underside of a vehicle.

Keeping Your Grey Tank Clean and Odor-Free

A grey water tank is a breeding ground for bacteria if left unmanaged, leading to the infamous “rotten egg” smell. The first line of defense is a proper vent line that extends above the roofline or through the floor, allowing gases to escape before they build up. Without proper ventilation, the pressure of filling the tank will force foul air back up through your sink drain.

Periodically flushing the tank with a mix of water and mild, eco-friendly dish soap or specialized RV grey-water treatments is essential. Avoid harsh chemicals that can damage seals or ruin the environment when you dump. If you notice a consistent odor, check your P-trap; keeping a small water seal in the pipe is the simplest way to block odors from migrating into your living space.

Dumping Your Grey Water: The Rules and Etiquette

The rules regarding grey water disposal vary wildly by location and are strictly enforced in many areas. Dumping grey water on the ground—even if it is just soap and water—is often illegal in protected wilderness areas and sensitive ecosystems. Always carry your grey water to an authorized dump station or a sewer connection.

Practicing good etiquette means never leaving a mess behind and keeping your hoses and couplings clean. Some dump stations are shared resources, and spending excessive time washing out your tank at a high-traffic location causes frustration for other travelers. Treat the environment and the facilities with respect, and you ensure that these dump sites remain open and accessible for the community.

The right grey water tank is one that fits seamlessly into your specific build while respecting the limitations of your travel style. By selecting a size that reflects your daily water use and ensuring a proper, vented installation, you eliminate the biggest points of friction in your mobile kitchen. Ultimately, a well-managed water system is a quiet, invisible component of your van, leaving you free to focus on the journey ahead.