Where are your water pipes located? Excluding the new supply from the wellhole pump about 90% of the piping supplying water to our house is under the concrete (150mm) floors. It was apparent that we had a leak recently (the pump was working intermittently to maintain the pressure although no water was being used) which was a bit of a headache. As it's been raining continuously recently we had no way of determining the source of the leak. However, the 36 hour cessation of rain lead us to discover that the leak was, in fact, not far from the pressure pump and thankfully under the ground and not under the house. The source has now been excavated and the leak repaired. I wouldn't have had a clue what to do if the leaking pipe had been under the concrete.