Key takeaways
- 12–15 gallons: Best for small travel trailers, short stays, and sites near a dump point. Expect more than one trip when the RV tank is larger.
- 18–21 gallons: A useful compromise for many couples and medium-sized trailers.
- 25–36 gallons: Better for larger holding tanks, extended stays, or reducing the number of trips.
- 42–45 gallons: Suitable only when the route is reasonably level and the user can manage a very heavy loaded tank.
The best portable waste tanks for RVs are the Thetford SmartTote2 for a refined all-around setup, the Barker Tote-Along for heavy-duty capacity and towing, and the Camco Rhino for a widely available range of sizes and accessories.
A portable waste tank lets you empty an RV holding tank without moving the vehicle to a dump station. The right choice depends less on the biggest advertised capacity than on whether your RV can safely fill, move, and store that tank. Compare capacity with your holding-tank size, then check wheel layout, handle strength, hose storage, towing method, and odor control.
Best portable waste tanks for RVs compared
| Tank family | Common capacities | Wheel and handle design | Hose storage | Best fit |
|---|---|---|---|---|
| Thetford SmartTote2 | 12, 18, 21, and 35 gallons | Two large wheels with a pull handle; compact models are easier to maneuver | Integrated storage area on many configurations for fittings and hose components | RVers who want a compact, well-organized tank for gray or black water |
| Barker Tote-Along | 15, 21, 25, 32, and 42 gallons | Large pneumatic-style wheels and a sturdy pull handle on larger models | Model-dependent; usually requires separate hose and fitting storage | Long-stay campers who need large capacity and better performance on uneven ground |
| Camco Rhino | 15, 21, 28, 36, and 45 gallons | Large wheels, molded tow handle, and fittings designed around the Rhino system | Dedicated compartment or accessory-based storage, depending on model | Buyers choosing among many capacities and compatible accessories |
Capacities and included accessories can vary by exact model number, so confirm the current product listing before buying. The table is most useful as a comparison of each product family’s design approach rather than a guarantee that every size includes identical equipment.
How to choose the right capacity
Start with the RV’s holding-tank capacity and the distance to the dump station. A portable tank should normally carry one practical transfer, not necessarily the entire RV system. A tank that is too small means multiple trips; one that is too large becomes heavy, difficult to pull, and harder to lift into position.
Use this calculation before choosing:
Full tank weight ≈ tank capacity in gallons × 8.34 pounds + tank weight + hose and fittings.
For example, a 21-gallon tank containing water-like gray water weighs approximately:
21 × 8.34 = 175 pounds
Add roughly 20–35 pounds for the empty tank, hose, and fittings, and the loaded unit may approach 200–210 pounds. Black-water contents vary, but the weight can still be substantial. This is why a 21-gallon tank may be practical for a couple with a nearby dump station but unrealistic if it must be dragged over gravel or pushed up a slope.
- 12–15 gallons: Best for small travel trailers, short stays, and sites near a dump point. Expect more than one trip when the RV tank is larger.
- 18–21 gallons: A useful compromise for many couples and medium-sized trailers.
- 25–36 gallons: Better for larger holding tanks, extended stays, or reducing the number of trips.
- 42–45 gallons: Suitable only when the route is reasonably level and the user can manage a very heavy loaded tank.
Head-to-head: wheel and handle designs
Two-wheel tanks
Two-wheel designs behave like hand carts. The handle carries much of the steering load, making them relatively predictable on pavement. They are usually easier to store because the body is narrower than a four-wheel wagon. Their weakness is balance: on rough grass, the operator must keep the tank tilted correctly, and a full large-capacity model can become difficult to control.
Four-wheel tanks
Four-wheel designs keep the tank more level and can feel stable when pushed across a campsite. They are useful for heavier capacities and short, smooth routes. However, fixed or small caster-style wheels can catch on gravel, and the tank may be awkward to turn in narrow spaces. Check the turning radius if your dump station is beside a fence, utility pedestal, or neighboring RV.
Handle and tow connection
A pull handle should be long enough to keep your feet clear of the tank and strong enough not to flex heavily under load. Some tanks include a connector intended for an RV bumper, while others are designed for manual pulling only. Do not assume that a bumper-mounted tow point is automatically safe: verify the bumper’s rating, the connector’s fit, and the route’s surface.
Towing a full tank behind a bicycle, golf cart, or vehicle is a poor substitute for a purpose-designed low-speed connection. Sudden turns can tip the tank, damage the valve, or pull a sewer hose loose. If the route is uneven, walking the tank is slower but gives you much better control.
Hose storage and setup convenience
Hose storage is more important than it sounds. A tank that accepts a cleanly capped hose and stores the adapters with it is less likely to leave fittings scattered around the campsite. Integrated storage also reduces the chance that a sewer hose will be placed on a picnic table, storage-bay floor, or other clean surface.
Before buying, check whether the tank includes all of these items:
- A sewer hose inlet that matches your existing bayonet fittings.
- A cap for the tank inlet and a cap or plug for the outlet.
- A clear elbow or transparent adapter if you want to verify flow.
- A vent or air-admission arrangement that prevents slow, surging drainage.
- Storage space large enough for the hose when it is fully drained.
Many kits include a hose but not the exact length or elbow needed for your RV layout. Measure the distance from the RV outlet to the tank inlet, including the height difference. A hose that is too short forces the tank close to the RV; one that is excessively long creates low spots where waste can remain.
Compatibility matrix for common RV layouts
| Your situation | Recommended size or design | Why it fits | What to avoid |
|---|---|---|---|
| Small trailer, 15–25-gallon holding tank, paved campground | 12–18-gallon two-wheel tank | Lower loaded weight and easy storage | 42–45-gallon tanks that exceed your lifting and route needs |
| Couple in a 30–40-foot trailer staying a week | 21–28-gallon tank with large wheels | Balances fewer trips with manageable towing weight | Small tanks that require repeated transfers |
| Motorhome with a rear or side sewer outlet | Tank with a long handle and secure tow connection | Allows the tank to be positioned without sharply bending the hose | Short-handle designs that place the tank directly under the coach |
| Uneven grass or gravel route | Large-wheel 25–36-gallon design | Better clearance and less wheel snagging | Small casters and oversized tanks that are difficult to steer |
| Limited storage compartment | Compact 12–21-gallon tank with integrated fitting storage | Smaller footprint and fewer loose parts | Wide four-wheel models whose dimensions exceed the bay opening |
Odor control: what actually works
A portable tank should be treated as a sealed waste container, not as an open bucket. Keep the inlet and outlet capped during transport and storage, rinse the tank after every dump, and leave it slightly ventilated only when the manufacturer’s instructions allow it. Do not store a black-water tank with untreated waste inside it.
Odor usually comes from residue in the hose, a leaking cap, a dry or damaged valve seal, or waste sitting in a warm tank. After emptying, run clean water through the hose and tank. A small amount of RV holding-tank treatment can help control residue, but use a product labeled as compatible with the tank and seals. Avoid household bleach, solvents, and harsh drain cleaners unless the manufacturer specifically permits them.
Which model should you buy?
Choose Thetford SmartTote2 for compact convenience
The SmartTote2 is a strong choice when storage space, organized fittings, and manageable dimensions matter more than maximum capacity. The 12- or 18-gallon versions suit smaller RVs, while the 21- and 35-gallon options cover larger layouts if the route is reasonably smooth.
Choose Barker Tote-Along for durable heavy-duty hauling
The Barker Tote-Along line makes sense for campers who prioritize a substantial handle, large wheels, and higher-capacity options. Its larger tanks are attractive for long stays, but the weight calculation matters: a full 32- or 42-gallon tank can be too heavy for one person on an incline.
Choose Camco Rhino for capacity choice and system compatibility
The Camco Rhino range is useful when you want several size options and a broad accessory ecosystem. A 15- or 21-gallon model is easier for routine use; 28 gallons and above reduce trips but demand a level route and careful handling.
Final buying checklist
- Match the tank’s capacity to your RV’s holding tank and expected number of transfers.
- Calculate the loaded weight before choosing a 32-, 42-, or 45-gallon model.
- Measure the RV sewer outlet height and the required hose length.
- Confirm that the wheels suit pavement, grass, gravel, or slopes at your campsite.
- Check bumper and tow-connector ratings before using any towing method.
- Choose integrated hose storage if your RV has limited exterior compartments.
- Confirm replacement caps, valves, seals, and fittings are available.
- Plan where the tank will be rinsed and stored without contaminating clean gear.
For most RV owners, a 21-gallon tank is the practical middle ground. Choose a smaller Thetford SmartTote2 when portability and storage dominate, a Barker Tote-Along when wheel strength and heavy-duty hauling matter most, or a Camco Rhino when you want a broad capacity range and compatible accessories. The best portable waste tank for RVs is the largest model you can move safely along your actual route—not the largest one that fits on paper.
