Key takeaways
- If your black tank is 30 gallons: 30 x 0.85 = 25.5 gallons. A 28-gallon tank handles it in one trip.
- If your black tank is 40 gallons and gray is 35 gallons: You cannot empty both at once with any single portable tank. A 28 or 32-gallon tank lets you empty the black tank in one trip and the gray in a second trip. A 15-gallon model would require 3 trips for the same job.
- If your RV has 20-gallon tanks (typical for small campers/vans): A 15 to 21-gallon tank is sufficient and much easier to store and tow when full. A 36-gallon tank would be overkill at 300+ lbs when full.
The best portable waste tanks for RVs are the Camco Rhino Heavy Duty series for most RVers due to its durable blow-molded construction and versatile capacities, the Barker 4-Wheeler Tote-Along for frequent campers who need large pneumatic wheels and easy towing, and the Thetford SmartTote2 LX for RVers who want integrated hose storage and auto-stop level indication.
Choosing the right size and design depends less on brand loyalty and more on your RV’s gray and black tank size, how far you have to tow to the dump station, and whether you need to lift the tank into a truck bed. A tank that is too small means multiple trips, while one that is too large is difficult to maneuver when full — water weighs 8.34 pounds per gallon.
Portable Waste Tank Comparison: Specs That Matter
Capacity is only the starting point. Wheel type, tank height, drain configuration, and hose compatibility determine how easily you can actually use the tank at a campground.
| Model | Capacity | Empty Weight | Full Weight (approx.) | Dimensions (L x W x H) | Wheels | Hose & Fittings |
|---|---|---|---|---|---|---|
| Camco Rhino 15-Gallon (39002) | 15 gallons | ~15 lbs | ~140 lbs | 34 x 20 x 13 in | 2 heavy-duty no-flat wheels | 3 ft sewer hose, 4 adapters included |
| Camco Rhino 21-Gallon (39004) | 21 gallons | ~18 lbs | ~193 lbs | 37 x 20 x 14 in | 2 heavy-duty no-flat wheels | 3 ft sewer hose, 4 adapters included |
| Camco Rhino 28-Gallon (39006) | 28 gallons | ~22 lbs | ~255 lbs | 39 x 22 x 14.5 in | 2 heavy-duty no-flat wheels | 3 ft sewer hose, 4 adapters included |
| Camco Rhino 36-Gallon (39007) | 36 gallons | ~27 lbs | ~327 lbs | 45 x 22 x 15 in | 2 heavy-duty no-flat wheels | 3 ft sewer hose, 4 adapters included |
| Barker 4-Wheeler Tote-Along 16-Gallon (10893) | 16 gallons | ~18 lbs | ~151 lbs | 36 x 20 x 13 in | 4 pneumatic rubber wheels | 3 ft hose, bayonet fittings |
| Barker 4-Wheeler Tote-Along 32-Gallon (30844) | 32 gallons | ~31 lbs | ~298 lbs | 44 x 23 x 15.5 in | 4 pneumatic rubber wheels | 5 ft hose, double bayonet |
| Barker 4-Wheeler Tote-Along 42-Gallon (30849) | 42 gallons | ~36 lbs | ~386 lbs | 48 x 24 x 16 in | 4 pneumatic rubber wheels | 5 ft hose, double bayonet |
| Thetford SmartTote2 LX 27-Gallon (40519) | 27 gallons | ~24 lbs | ~249 lbs | 40 x 22 x 14 in | 2 front wheels + rear casters | 3 ft hose, built-in hose storage, AutoStop level gauge |
All three lines use blow-molded polyethylene, but the construction differs: Camco Rhino uses a stepped low-profile design for stability during towing, Barker uses a single-piece tank with a full-length double handle for hand-towing like a wagon, and Thetford uses a two-wheel design with a front steer handle and integrated ladder hook for hanging on the RV ladder.
How to Choose the Right Capacity: A Worked Calculation
Do not guess. Match the portable tank to your RV’s holding tanks. Most travel trailers and fifth wheels have 30 to 40-gallon black tanks and 30 to 50-gallon gray tanks combined. Class B and C motorhomes often have 20 to 30-gallon tanks total.
Use this formula:
Required Portable Capacity = Largest Single Holding Tank x 0.85
The 0.85 multiplier accounts for the fact you rarely dump a completely full tank and gives you a margin to avoid overfilling the portable tank, which is a common cause of spills.
- If your black tank is 30 gallons: 30 x 0.85 = 25.5 gallons. A 28-gallon tank handles it in one trip.
- If your black tank is 40 gallons and gray is 35 gallons: You cannot empty both at once with any single portable tank. A 28 or 32-gallon tank lets you empty the black tank in one trip and the gray in a second trip. A 15-gallon model would require 3 trips for the same job.
- If your RV has 20-gallon tanks (typical for small campers/vans): A 15 to 21-gallon tank is sufficient and much easier to store and tow when full. A 36-gallon tank would be overkill at 300+ lbs when full.
Weight is the limiting factor. A 36-gallon tank at 327 lbs full cannot be lifted. It must be towed slowly (under 5 mph) to the dump station using a tow bracket on your hitch. A 15 to 21-gallon tank at 140 to 193 lbs can be pulled by hand over short, flat distances.
Decision Matrix: Which Tank Fits Your Situation
| Your Situation | Recommended Capacity | Best Design Choice | Why |
|---|---|---|---|
| Couple in 25-30 ft travel trailer, staying 4-7 days without sewer hookups | 28 to 32 gallons | Camco Rhino 28 or Barker 32-Gallon 4-Wheeler | Handles one full black tank dump in one trip, balances weight and storage size |
| Family in large fifth wheel or toy hauler, 40+ gallon tanks | 36 to 42 gallons | Barker 42-Gallon or Camco Rhino 36 | Minimizes trips for large tanks, requires vehicle tow bracket |
| Solo or couple in Class B/C or small trailer, limited storage | 15 to 21 gallons | Camco Rhino 15 or 21 | Light enough for hand towing, stores in basement compartment or truck bed easily |
| Campground with gravel, grass, or uneven dump station path | Any size, prioritize wheels | Barker 4-Wheeler with 4 pneumatic wheels | Large air-filled wheels roll over gravel and curbs; small no-flat wheels can dig in |
| Need to transport waste uphill or long distance (500+ ft) | 27 to 32 gallons with tow adapter | Thetford SmartTote2 LX or Barker with tow bracket | Integrated tow handle and hose storage prevent dragging and leaks during long tows |
Key Features Compared: Wheels, Handles, Hose, and Odor Control
1. Wheel Durability and Towing
Two-wheel designs (Camco Rhino, Thetford) are lower profile and more stable when stored, but all the weight rests on two points when moving. They work best on paved campground roads. Four-wheel wagon-style designs (Barker) distribute weight and use pneumatic tires that absorb bumps, but require checking tire pressure and are more prone to flats if not maintained. All models should be towed at walking speed. Most include a metal tow bracket that attaches to a standard 2-inch hitch ball for slow vehicle towing. Never tow at campground driving speeds.
2. Hose Compatibility and Emptying Convenience
Standard RV sewer hose is 3-inch bayonet. All three brands use this standard, so your existing RhinoFLEX or similar hose will connect. What differs is emptying:
- Camco Rhino has a built-in gate valve and a removable sewer hose with two bayonet adapters and an elbow. The low drain outlet and dual rinse ports help flush the tank.
- Barker has front and rear 3-inch drain valves, allowing you to drain from either end at the dump station without repositioning.
- Thetford SmartTote2 LX has an extra-wide fill opening, a front-mounted gate valve, and the AutoStop indicator that shows when the tank is full to prevent overfilling. Its integrated hose can be stored inside the tank cavity.
Look for a tank with both a top fill port and a bottom drain valve. Top-fill-only models require tipping to empty, which is messy and difficult when heavy.
3. Towing Handles and Storage
Handle design affects control. Camco uses a removable steel tow bar that doubles as a handle. Barker uses a long, double-bar handle that allows two-handed pulling and steering like a wagon. Thetford uses a folding front handle with a hook to hang the tank on an RV ladder for transport. For storage, measure your pass-through compartment: a 36-gallon tank at 45 inches long will not fit in many shorter bays. A 21 or 28-gallon low-profile tank is the most common sweet spot for storage.
4. Odor Control
No portable tank is odor-proof if not sealed and cleaned. All use vented caps to prevent pressure buildup. Odor control comes from:
- Tight-sealing bayonet caps and gate valves with O-rings
- Rinsing with a dedicated tank rinser or built-in rinse port after each dump
- Using an RV tank deodorizer tablet in the portable tank if you must store waste for more than a day
- Storing the tank with valves open and caps off after thorough rinsing to allow drying and prevent mildew
Durability and Ownership Realities
Portable waste tanks are simple but not maintenance-free. Here is what actually wears out:
- Gate valves and O-rings: The first failure point. Sand and grit wear the valve seal. Rinse the valve after each use and apply silicone lubricant to the seals twice a season. Replacement valves are inexpensive and use standard 3-inch Valterra-style fittings.
- Wheels and axles: No-flat solid wheels can crack at the hub after years of UV exposure. Pneumatic wheels need air pressure checks and can go flat. Store the tank out of direct sun when not in use.
- Hose and bayonet fittings: The included 3-foot hose is short by design to prevent sagging during filling. It will crack at the ends first. Replace it with any standard 3-inch RV hose. Keep spare bayonet caps — losing a cap means odor and leaks in storage.
- Tank body: Polyethylene is rugged but can develop stress cracks if dropped when full or dragged over rocks. Never drag a tank without wheels, and do not overfill past the indicator.
Common mistakes to avoid: overfilling (leave 2-3 inches of air space), towing too fast (wheels and brackets are rated for under 5 mph), storing with waste inside, and using household cleaners that degrade seals. Flush the portable tank at the dump station with a non-potable rinse hose, not your fresh water hose, and flush your RV black tank before the gray tank so gray water can rinse the portable tank.
Market pricing in 2026 generally falls into three tiers: compact 15 to 21-gallon models in the lower range, mid-size 27 to 32-gallon models in the mid range, and large 36 to 42-gallon four-wheel models at the premium end due to wheel and frame cost. Kits that include hoses and tow brackets typically cost slightly more than tank-only options.
Final Picks by RV Size
Best Overall for Most RVers: Camco Rhino 28-Gallon. It covers a single full black tank for most trailers, stays under 260 lbs when full, includes all hose adapters, and stores more easily than 36+ gallon models.
Best for Large RVs and Long Stays: Barker 4-Wheeler 32 or 42-Gallon. The four pneumatic wheels and wagon handle make moving 300+ lbs over grass and gravel realistic, and the dual drain valves simplify dumping. Ideal if you have a large tow vehicle and space to store it.
Best for Small RVs and Easy Storage: Camco Rhino 15 or 21-Gallon. Lightest to handle by hand, fits in compact storage bays, and is sufficient if your holding tanks are under 25 gallons.
Best for Convenience Features: Thetford SmartTote2 LX 27-Gallon. The built-in hose storage, level gauge, and ladder hook address the small annoyances of transport and overfilling for campers who move frequently between sites without sewer.
If you are unsure between two sizes, choose the smaller tank that can empty your largest holding tank in one trip. An extra trip is easier than wrestling an overweight tank or finding storage for a tank that is too long for your compartment.
Frequently Asked Questions
Can I dump gray and black water together in one portable tank?
You can, but do not mix them if you plan to reuse the gray water or if campground rules separate them. Most RVers dump black first, rinse the portable tank, then dump gray. If you combine them, treat the entire load as black water at the dump station.
How do I clean a portable waste tank after use?
At the dump station, drain completely, then use the station’s non-potable rinse hose through the fill port or dedicated rinse port. Open the gate valve and flush until water runs clear. Leave valves open to air dry before storing. A periodic rinse with an RV tank cleaner helps prevent buildup.
Do I need a separate hose for the portable tank?
Yes, use a dedicated sewer hose for waste transfer. Keep your fresh water hose completely separate to avoid cross-contamination. The short hose included with most tanks is intentional — a long hose sags and traps waste.
