The keys to efficiency

Anyone who has lived in a house with radiators would know what these keys are for. For those of you who have never seen keys like this, let me explain. On each radiator is a small valve where these keys fit. If the radiator begins to gurgle too much, it means there is air in it and it needs to be released so the radiator can work efficiently. Insert the key into the valve, give the valve a few turns until it starts to hiss. After a bit some very dirty water will join in with the hissing and then the job is done. It's a very easy process but certainly makes a big difference. Just what you wanted to know today!