At least one in four of the rural water supplies in most developing countries is out of order, and has frequently been broken down for some time. It is best to try to build a 'fail-safe' character into rural water supplies so that one small fault is not likely to put the whole system out of action. As a general rule the cheaper and simpler the technology, the less maintenance it requires, the more reliable it is in practice and the easier to repair under village conditions. The major exception is in the choice of hand pump, where the more robust and reliable pumps are usually more expensive and more difficult to repair.