We moved into a house about 5 years ago and the water pressure was 110 lbs. So I put a reducing valve on and set it at 55 lbs. ( on city water ) Everything has been fine except for the last week we have had low water pressure. When you turn on the water anywhere you have good pressure to start but after a minute it goes down to around 25 to 30 lbs. I put a gauge on the faucet and it read 55 lbs. I haven't done any digging to crimp a pipe....... Anybody know what could be the problem or where to start?