In sealed systems such as heating systems micro leak result in a slow and constant loss of pressure with no obvious cause. Pressure loss will eventually leak to boilers failing and indicating low system pressure, plumbers can be called out to top up the system at expense. Many systems have to be constantly topped up by heating engineers or the residents themselves sometime maybe once a year or every few months, other cases can be even more frequent especially in smaller systems with a lower total water content one leak makes a greater difference.
Micro leaks are more likely to occur in heating and hot water pipes as the water is hotter so the rate of evaporation is faster.
Loss of pressure through micro leaks will result in closed system such as heating circuits and wet cooling circuits running on low pressure. This will reduce efficiency. Modern domestic boilers will activate a fault code when water pressure is low this protects the heat exchanger.