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Does anyone give me some idea what happened ? I put a water pressure gauge right after the main water main. To see there is any water leak in the system. beginning few months the water pressure hold at 68 psi. one day the water no longer hold, If I shut down the water main, the gauge start losing pressure. about 5 minutes, go to 60 psi, another 5 minutes, go to 50, then 40, then after a while go to 0. This has been few months already, I check the whole house, do not see any faucets or toiler leaking, any water pipe expose I can see I checked, no leaking. check the sheetrock where the pipe travel inside, do not see any wet. It is very strange. Talk to the plumber who installed the system, he just said no problem. But when I open the water main again. I can hear the water traveling to fill up the system. Definitely somewhere leaking. My water system is after water main, one go to hot water system, one go to house water. I did try to cut off the hot water system, it is still the same, water pressure drop. Any comment appreciated.