Awesome. Simple and to the point. Thank you.

A main drain test "drain drop" should be performed anytime the control valve has been closed to ensure control valve is fully open and proper flow. Same reason we flow test hydrants to check for obstructions in the water supply. Residual supply pressure should usually not exceed 10 psi drop when 2" main drain is fully open.

In the United States an Excess Pressure Pump is not used in the trim, and the gauges will show the same pressure at the time of set-up. If the Water supply is a variable supply, once the pressure increases the top gauge will show the highest pressure that the system has been exposed to, while the lower gauge will show the current pressure.

Is it mandatory in nfpa? Where is the best position to install is it in pump room or outside it? Is the only propose of it to get alarm sound?

But why is mechanical alarm required When we have detectors connected to alarms

1:05 a WHAT CHAMBER