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Working pressure is at the meter whilst appliance is working to check governor/regulator
Operating pressure is burner pressure at burner to check gas valve is set correctly
Inlet pressure is testing pipework whilst appliance is working
Standing pressure is the useless one
Thats how I know it
Reply to the thread, titled "Working Pressure versus Operation Pressure" which is posted in Gaining Plumbing Experience on Plumbers Forums.
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