As a rough rule of thumb, if there are more or the same number of bedrooms in your house than people, check out getting a meter. (moneysavingexpert.com)
They can also simply enter their location and home requirements, such as number of bedrooms or price, and see immediate results. (rismedia.com)
If you've more or the same number of bedrooms in your house than people, you're probably better off with a water meter. (theguardian.com)