A drain-down valve is a small valve installed at the lowest points of a heating or water system to allow it to be drained for maintenance, alteration or freezing protection. UK installations follow BS EN 215 for thermostatic radiator valves and BS EN 1213 for fittings, with drain valves used in conjunction with isolation valves to enable a controlled drain down. The valve is typically operated with a square key and includes a threaded outlet for a hose connection. Drain-down valves are critical when servicing combination boilers, unvented cylinders and radiators in flats across central London. They are also used to drain external pipework before periods of severe frost. Regular inspection helps ensure that the seal does not fail unexpectedly, which can be a hidden cause of low system pressure.
Drain-down valve
Valve fitted at low points to drain a heating or water system for maintenance.
