Atwood GC10A-4E Replacement: Best Tankless RV Water Heater Upgrades 20

What's Going On

You're absolutely right that there's no direct plug-and-play replacement for your Atwood GC10A-4E with a gas-only instant unit while keeping the electric capability. Your instinct about keeping the electric option is spot-on - when you're plugged into shore power at a campground, running on electric is essentially free compared to burning propane. The GC10A-4E is actually pretty efficient on gas, so switching to an instant unit might not save you as much propane as you'd expect, especially since instant units need to burn gas every time you turn on hot water rather than maintaining a tank temperature.

Most RVers who've made this switch report mixed results. While instant units provide endless hot water, they require significant modifications to your gas lines, electrical connections, and venting systems. The Atwood GC10A-4E uses a specific mounting pattern and connection setup that doesn't match standard instant units like the Girard or Truma models.

Why This Happens

The lack of direct replacement options stems from the unique design of the GC10A-4E. This unit was designed as a combination electric/gas tank system with specific mounting brackets, a 10-gallon capacity, and electric and gas heating capability. Instant water heaters operate on completely different principles - they heat water on-demand as it flows through, requiring different gas flow rates, electrical requirements, and venting configurations.

Your concern about gas usage is valid but needs context. The GC10A-4E burns gas to maintain tank temperature, but once heated, it holds that temperature well with good insulation. An instant unit burns gas every single time you use hot water, which can actually consume more propane if you're frequently using hot water throughout the day. The electric element on your current unit draws about 1440 watts but costs pennies per hour when on shore power.

The mounting and connection differences are significant. The GC10A-4E mounts in a specific rectangular opening with particular clearance requirements, while most instant units have different dimensions and mounting requirements. The gas line connections, electrical hookups, and exhaust venting all differ substantially between tank and instant systems.

Getting Ready

WARNING: Gas line modifications and water heater installations involve serious safety risks including potential gas leaks, carbon monoxide exposure, and fire hazards. This type of work requires professional installation by certified technicians familiar with RV propane systems and local codes. Improper installation can result in dangerous gas leaks that may cause explosion or death.

Before considering this conversion, gather some data on your actual propane usage with the current system. Monitor how much propane you use over a typical camping period, noting when you're on electric versus gas-only operation. This will give you a baseline to compare against potential savings from an instant system.

If you decide to proceed, you'll need to research instant units that can physically fit in your available space. Popular replacement options include units similar to the Girard GSWH-2 or Truma AquaGo series, but you'll need to verify the correct part for your model (verify with dealer) and measure carefully - you may need to modify the exterior compartment opening. You'll also need to assess your gas line capacity, as instant units typically require higher BTU input rates than tank systems.

Consider your hot water usage patterns. If you typically take quick showers and don't use much hot water simultaneously from multiple fixtures, an instant unit might work well. However, if you often run hot water for extended periods or from multiple taps, the GC10A-4E's tank capacity might actually be more convenient.

Budget for professional installation. This isn't typically a DIY project for safety reasons, and you'll want proper permits and inspections for gas system modifications.

Walking Through the Fix

WARNING: The following steps involve gas system modifications that must be performed by qualified professionals only. Do not attempt gas line work without proper certification and equipment.

The conversion process involves several major steps, starting with removing the existing GC10A-4E system. A qualified technician will need to disconnect the gas line, electrical connections, and water lines, then remove the mounting hardware. Save all hardware and fittings - some may be reusable depending on your chosen replacement unit.

Next comes modifying the mounting opening. Most instant units have different dimensions than the GC10A-4E, so you'll likely need to enlarge or modify the exterior compartment opening. This requires careful measurement and potentially cutting into the RV's exterior wall, which should be done professionally to maintain water-tight integrity.

Gas line modifications are critical and must be performed by certified professionals. Instant units often need larger diameter gas lines or higher pressure than tank systems. The gas valve and regulator system may need upgrading to handle the different flow requirements. All gas connections must be pressure tested and inspected for safety compliance.

The electrical system will need complete rewiring. While you lose the 120V heating element, instant units typically require 12V power for ignition systems and control circuits. You'll need to run new 12V lines from your RV's electrical panel to the unit location. The existing 120V wiring should be properly disconnected and capped.

Venting requirements differ significantly between systems. The GC10A-4E has a specific exhaust configuration that won't work with instant units. You'll need to install new venting that meets the instant unit's specifications, which may require cutting additional holes in your RV's exterior walls.

Beyond DIY Territory

This conversion definitely falls into professional installation territory due to the gas system modifications and structural changes required. Working with propane systems requires specific certifications and knowledge of safety codes. Many RV service centers won't warranty work that involves significant gas system modifications, so choose your installer carefully.

Consider the cost-benefit analysis seriously. A quality instant water heater system will cost $800-1500 plus installation fees that can easily reach $1000-2000 when you factor in all the modifications needed. Your existing GC10A-4E, if functioning properly, is actually a reliable and efficient system that many RVers prefer for its tank capacity and dual-fuel capability.

Before committing to this major modification, try optimizing your current system first. Ensure the GC10A-4E is properly maintained, the anode rod is replaced regularly, and the unit is well-insulated. Use the electric element whenever possible when on shore power, and only run on gas when boondocking. This approach might give you the efficiency you're looking for without the expense and complexity of a complete system replacement.

If you absolutely must have endless hot water, consider whether upgrading to a larger capacity tank system might meet your needs better than switching to instant. The Suburban SW10DE or similar units offer more capacity while maintaining the dual-fuel capability you value.