How To Drain Radiator. Open the drain valve by turning it counter-clockwise. All the water will start to drain out.
Let the system cool down for at least 30 minutes. Turn off the gas to the boiler system. After the engine cools down remove the radiator cap.
Refill the radiator to within an inch of it overflowing.
The radiators pressure cap is located at the top of the radiator. Turn off the gas to the boiler system. Install a tube on the radiator drain. The water will begin to drain from the boiler.
