Yes, geothermal HVAC systems for irrigation preheating can be integrated with existing irrigation systems. The heat exchanger can be connected to the existing irrigation piping, and the geothermal system can be designed to provide supplemental heat as needed. Integration with existing systems may require modifications to the piping and control systems, but can offer significant energy savings and environmental benefits. A thorough analysis of the existing system and geothermal system design is necessary to ensure seamless integration and optimal performance.