Sounds like air in the lines as SecretSquirrel mentioned. One thing I do is connect a water source to the City Water connection. Feed water into City water and open faucets one at a time. This will purge air out of the lines. Also open the pressure relief valve near the top of the hot water tank to purge air out of the tank.
Hope this helps
2014 Micro Lite 19fd
2015 F-150 5.0L V8 XLT Crew Cab, 4x4, Tow Package, 36 gal tank, 3.55 locker, 1891 payload, Integrated Brake Controller, Roadmaster Active Suspension
Wooden Spoon Survivor