To open hot water for radiators, follow these steps: First, ensure the heating system is off and cool. Locate the bleed valve, typically found at the top of the radiator. Use a radiator key or flat screwdriver to gently unscrew the valve. Allow water to drain until it stops flowing, indicating trapped air has been released. Refasten the valve and restore heat to test functionality. Repeat if necessary.

This process addresses airlocks, which reduce heat distribution and efficiency. According to the U.S. Department of Energy, airlocks can cause 15-20% energy loss in forced-air systems and 10-15% in hot water systems. Trapped air increases thermal stress, leading to pipe corrosion and leaks. A 2021 study by the Building Performance Institute found that 30% of radiator failures stem from improper bleeding, costing homeowners an average of $450 annually in repairs. Regular bleeding maintains system pressure, preventing water oxidation and prolonging radiator lifespan. The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) recommends bleeding radiators every 1-2 seasons or when heat output drops. Neglecting this can escalate energy bills and damage HVAC components, emphasizing the importance of timely maintenance.