How can I tell if I have a leaky loo?

It's the most common leak in the house, and the easiest one to miss. Nothing drips on the floor and nothing pools — the water simply runs quietly down the back of the pan and away, day and night.

The paper test is reliable because the trickle is often too slow to see against white porcelain.

You don't have to take our word for the scale of it, either. United Utilities — who supply every home in Macclesfield — reckon a leaky loo in the North West wastes somewhere between 200 and 400 litres a day, and that on a metered supply it can cost you up to £400 a year. They'll post you free leak-detection strips to check with: you drop one in the cistern, wait, and if the colour appears in the pan without you flushing, that's your answer.

The usual culprits are a worn flush valve or flapper washer, a float or fill valve set too high so water runs into the overflow, or grit holding a seal open. It's normally a cheap part and a short visit — and it pays for itself quickly if you're on a meter.