High water pressure issue from hot water heater
If you get a burst of water flow which seems like an over-pressure, it may be time to replace the pressure reducing valve in the water supply line.I would put a pressure gauge on the cold water. Then run the water for a few seconds until the pressure stabilizes in the line. Stop running water and see if the pressure gauge rises as I suspect it will. You can buy a pressure gauge that will screw onto any outlet that will accept a garden hose. Buy at a hardware store like Ace or Home Depot, or Lowes.