Hi Justin. You can consider ...

Hi Justin. You can consider use of tracer chemicals (even chlorine) then sample the pipe route. The dilution effect will indicate the size of any leak. However the chemicals must be considered very carefully. If the pipe can be drained then use pressurised air and look for the bubbles. If it cannot be isolated then consider using helium mixed into the water. For permanent monitoring why not install high accuracy meters at either end and monitor the difference. Pressure monitoring may be used as well.