Final answer:
The hose used to connect a propane supply to a domestic water heater must be specifically approved and labeled for propane use, not for natural gas, and fitted with specialized connections for safety.
Step-by-step explanation:
When connecting a propane supply to a domestic water heater, it's vital to ensure that the hose used adheres to specific standards for safety and functionality. The correct choice would be a hose that is approved and labeled specifically for propane use. This is because propane and natural gas systems operate at different pressures and have different requirements. Therefore, it wouldn't be appropriate to use a hose rated for natural gas for a propane system. Additionally, there's usually no specific length requirement like the 10 feet mentioned in the question. Installation practices may vary, but in many cases, hoses are fitted with specialized connections rather than generic compression fittings to ensure a secure and leak-free seal.