1. Gray Water Tank

The Thetford 12 Gallon RV Waste Holding Tank, Model 40711 is a widely chosen gray water tank for campervan and RV conversions due to its versatile size, robust construction, and compatibility with a range of plumbing layouts.

What Makes It Ideal for Campervan Conversions

• Compact Size: At 12 gallons, it strikes a balance between sufficient capacity and space efficiency, making it suitable for most van layouts without consuming excessive underbody or interior storage space.
• Proven Durability: Manufactured by Thetford, a leading RV sanitation brand, it is designed to withstand vibrations, UV exposure, and temperature variations commonly encountered in mobile setups.
• Universal Fit: The tank’s standardized fittings and flat-bottomed design simplify integration into DIY and professional builds.

Key Features and Benefits

• 12-Gallon Capacity: Provides adequate holding for gray water from sinks and showers for smaller families or solo travelers, usually lasting 2–3 days between dumps for moderate use.
• Heavy-Duty Construction: Made from high-density polyethylene (HDPE), which resists cracking, impact damage, and chemical corrosion commonly caused by soaps, food particles, and detergents[4].
• Multiple Inlet/Outlet Ports: Facilitates flexible plumbing for both side and bottom drain installations.
• Odor Control Compatible: Works seamlessly with treatments like Thetford Grey Water Fresh Concentrated to reduce odor and deposits[1][2][3].
• Easy Maintenance: Smooth interior surfaces minimize buildup and simplify rinsing/cleaning.

What to Look for When Buying

• Capacity Suitability: Ensure 12 gallons matches your daily usage and trip duration—larger groups or extended boondocking may require bigger tanks; for solo or couple weekend use, 12 gallons is typically optimal.
• Mounting Locations: Confirm tank dimensions fit your planned install location (underbody, inside cabinetry, etc.).
• Ease of Drainage: Check that the tank’s outlet location and size align with your hose and dump station setup.
• Quality of Materials: Favor tanks made of UV-resistant, seamless HDPE for long-term reliability.
• Accessory Compatibility: Verify that it is compatible with vents, sensors, and cleaning chemicals.

Common Mistakes to Avoid

• Ignoring Maintenance: Not treating the tank regularly with odor-control and cleaning agents can result in foul smells and buildup[1][2][3].
• Improper Mounting: Failing to secure the tank adequately can cause leaks and wear from vibrations.
• Overestimating Capacity Needs: Installing a tank larger than necessary wastes space and adds weight; underestimating leads to frequent dumps.

Best Use Cases

| Use Case | Suitability |
|--------------------|-------------------------------------------------|
| Weekend Warrior | Excellent—ample for 2–3 days for 1–2 people. |
| Full-Time Living | Sufficient for solo/couple with regular dumps; may require more frequent emptying for families or group travel. |

Budget Considerations and Value Analysis

• Mid-Range Pricing: Thetford tanks tend to cost more than generic options but deliver superior build quality, longevity, and a warranty backed by a trusted RV supplies brand.
• Long-Term Value: Investing in a reputable tank reduces the risk of leaks, odors, and costly replacements, especially over years of constant use.
• Accessory Costs: Consider budgeting for cleaning treatments and installation accessories to maintain optimal performance and hygiene[1][2][3].

Selecting the Thetford 12 Gallon Model 40711 gray water tank provides a reliable, space-efficient, and RV-proven solution for most campervan conversions, with the right balance of size, quality, and support for both casual and full-time travel.

A gray water tank collects wastewater from sinks and showers in campervans and RVs, separating it from black water tanks (toilet waste)[1][3]. Top alternatives in the van life category include:

Top 3–5 Gray Water Tank Alternatives (2025):

• Valterra R8030 Gray Water Tank (15 gallons, ABS, underslung design)[2]
• Class A Customs Universal Tank (multiple sizes, low-profile, potable/non-potable use)
• RecPro RV Water Tank (various shapes, heavy-duty plastic)
• Camco Portable Waste Tank (portable, wheeled, external disposal)
• DIY Freshwater/Graywater Tank (custom polyethylene, fits unique layouts)[2][4]

Comparison Table: Gray Water Tank Alternatives

| Product | Pros | Cons | Price Range |
|------------------------|------------------------------------|----------------------------------------|------------------|
| Valterra R8030 | Lightweight, rust/algae resistant, easy install, many sizes | Cracks under vertical pressure, must vent, no gauge | $70–$150 |
| Class A Customs | Fits wheel wells, potable approved, durable | Heavy, limited shape options | $90–$200 |
| RecPro | Heavy-duty, fits RV/van dimensions | May need separate venting/fittings | $75–$185 |
| Camco Portable | Portable, easy dump, no install | Low capacity, external only | $50–$120 |
| DIY Polyethylene | Custom design, fits unique spaces | Labor/skill required, potential leaks | $50–$250 |

When to Choose the 1. Gray Water Tank vs Alternatives:

• Opt for the Valterra R8030 or similar fixed tank if you want an affordable, durable, permanent underslung solution with varied size options.
• Choose Class A Customs or RecPro for specific shape requirements or potable water compatibility.
• Use Camco Portable for flexibility in locations without easy dump access, or when you need to avoid modification.
• Go DIY if your van has unique layout constraints or you prioritize exact fit over convenience.

Performance Differences for Van Life Use Cases:

• Fixed tanks (Valterra, RecPro, Class A): Better for extended off-grid use, less frequent emptying, and stealth camping thanks to inconspicuous installation[2][4].
• Portable tanks (Camco): Preferred for short trips, campsites with dump stations, or rental vans needing temporary solutions.
• DIY: Best for maximizing storage in odd-shaped spaces but may need careful sealing and installation to avoid leaks.

Capacity, material durability, and installation flexibility are decisive; high-quality fixed tanks offer better long-term reliability for serious van life. However, portable tanks excel in maneuverability and ease of emptying, while DIY tanks adapt to any custom build with potential trade-offs in construction time[2][4]. Most options range $50–$250, with fixed ABS/poly tanks typically $70–$185.

Installing a gray water tank in a campervan requires careful planning and proper execution. Here's a comprehensive guide based on experienced van builders' insights.

Step-by-Step Overview

Planning and Preparation: Choose your tank location, typically under the van behind the driver's seat where chassis ribs provide mounting points[2]. Measure the space to ensure your tank fits - Sprinter ribs are often 36" apart, which works well for standard tanks[2].

Tank Preparation: Install all fittings before mounting, including fill ports, vent lines, and drain valves. Apply Teflon tape to threaded connections and add rubber padding where the tank contacts the frame[1].

Mounting Process: Use custom steel brackets attached to existing chassis mounting points. A floor jack is essential for positioning the tank - borrowing a neighbor's lift jack makes this much easier[2]. Install brackets one at a time without removing multiple bolts simultaneously[1].

Tools and Materials Needed

Essential components include a 15-gallon tank, steel mounting brackets, plusnuts, bulkhead fittings, barbed adapters, drain hose, air vent components, and an electronic solenoid valve for convenient dumping[1]. A 90-degree drill adapter is crucial for accessing tight spaces[2].

Common Mistakes to Avoid

Never compress the fuel tank during installation[1]. Use slotted brackets instead of round holes to avoid alignment issues with Mercedes tank straps[1]. Ensure flexible hoses are cut to proper length - this often requires multiple iterations[3].

Safety and Professional Considerations

Estimated time: 6-8 hours for experienced DIYers. Consider professional installation if you're uncomfortable working under the vehicle or lack proper jack equipment. Always support the tank properly during installation and test all connections before final assembly.