You can use a radiator to drain a central heating system. Also seek expert advice from professionals such as Chislehurst Plumbers if you are not confident.This operation takes much more time to complete prompting most people to fit a drain cock initially. In order to drain from a radiator it is best to remove the radiator from the wall. With the radiator off the wall, connect a hose which should be a flexible hose with a piece of copper pipe around 4-6 inches long pushed into the end and held secure with a jubilee clip and fit a flexible tap connector to the copper pipe via a push fit connector. Valves come in two sizes newer being ? and older being ? so you need either a 15mm to ? or 15mm to ? flexible tap connector to do the job. Dont panic about mixing metric and imperial measurement as your local merchant will understand. Once the flexible connector is attached to the radiator, tighten by hand and then with an adjustable spanner. Run the hose outside to the garden or drain point in order to move the water remembering the water will be dirty. Open the valve on the radiator slowly and listen for the water running away. Once you are happy that there are no leaks the open the valve fully.Now if you are unlucky and dont have a hosepipe then you will have to collect the discharging water in a suitable container which will take a really long time. Of course having sorted your leak or leaks you must now replace the radiator back on the wall and fill the system again. It is not advisable to undertake work of this nature yourself unless you have previous experience and can be fraught with pitfalls and be quite dangerous. You can always call in your local Chislehurst Plumber and get a quote from him as this means that any work carried out is guaranteed.