How to fit a drain cock without draining down the heating system

Need to drain down your heating system only to find there is no drain cock or the one you have is jammed fast? Here is the easy way to fit a new one. VIDEO UPDATE. (2023) After 2 years in the system the valve becomes blocked due to the small hole bored in the pipe and the piece of copper that was cut out also helps block the drain cock. SO ONLY FIT FOR A TEMPORY JOB . Use it to drain out then fix your old drain valve. Visit Al`s Amazon plumbing shop .http://www.amazon.co.uk/shop/dereton33