If you have a conventional gravity-fed system (the kind with a cold water tank in the loft), sometimes the best tool is patience.

Old Man Higgins lived in a crooked cottage at the end of Puddledown Lane. One morning, he turned on his kitchen tap, and instead of a healthy rush of water, he got a pathetic sputter, a deep gurgle , and then nothing but a sad sigh of air.

While it sounds like a mechanical failure requiring a plumber and a second mortgage, an airlock is usually just a simple case of physics gone wrong. Air, being lighter than water, has become trapped in a high point of your pipework, forming a "bubble" that blocks the flow, much like a cork in a bottle.

This is the gold standard of DIY plumbing fixes. It uses the superior pressure of your cold mains water to bully the air bubble out of the hot water pipes.