It depends where gauge is sited. A gauge on a T will read about 10% less than the actuall pressure when water is flowing, but will read the correct pressure when the flow is closed IE lance in lay down. So if you have a 200 bar machine and it reads 200 bar when lance is in lay down, but drops to 175 bar when you pull trigger thats about right as 10% of 200 = 20 so 200 minus 20 = 180bar
Unless..... Things have changed with your machine since new. Obviously you know your machine, has the pressre drop always been so? If not sounds like your drawing air, restricted filter(s) etc During this pressure drop does the machine/hoses etc vibrate more than normal, if it does this is cavitation and it needs sorting before you need a wad to fix it!
