How to loose a rusty drain cock in central heating system

[michael2008]

The drain cock in my central system is rusty outside, looks green. I couldn't unscrew it. How can I unscrew it and drain the central heating system. Thanks for any tips!

[justlead1]

Hi. There are two type of Doc. One that screws into a 1/2" bsp. fitting or the type that are soldered into a capillary fitting. It is not unusual to find this problem, with the soldered type unless the washer assembly is removed prior to heating the washer often welds its self to the seating. Any how. Turn off the supply to the heating system. Find a rad at low level, turn off both wheel head and lockshield valves. have a rag handy and remove plug at to of rad, once removed screw in a 1/2" fitting that will allow the conection of a hose. (Doc Or copper to irn with a small peice of 15 mm copper tube.) fit hose and open valves on rad. this will drain down most of system and reduce the pressure at the point of failed fitting allowing you to remove and replace with less flooding risk. Go Luck