Short answer
Low commercial gas pressure is usually caused by one of five things: an undersized or partially blocked service or meter, a faulty or wrongly set meter regulator, undersized installation pipework for the connected load, added appliances that exceed the original design, or a supply network problem. Measuring standing and working pressures at the meter and at appliances isolates which one it is.
Diagnosis method
1. Standing pressure at meter outlet — low suggests the regulator or supply. 2. Working pressure at meter outlet under full load — a large drop from standing suggests meter, regulator or service restriction. 3. Working pressure at appliance inlets — a large drop from the meter outlet suggests installation pipework.
Upstream causes
Faulty meter regulator (diaphragm damage, debris on the valve seat, wrong spring), filters choked with debris, meters undersized for the load, or network pressure low on cold days. Meter and service issues are the responsibility of the meter asset manager or gas transporter and must be reported to them.
Installation causes
Pipework sized for the original load but extended with extra appliances, long runs of small-bore pipe, excessive fittings, debris or water in the pipe, and partially closed or failed isolation valves.
Fixes
Upsizing pipework, re-routing, upgrading the meter, installing a booster (with gas transporter approval) or staging appliance demand. The right fix depends on where the pressure is being lost.
Figures are typical for UK natural gas. The current edition of the relevant IGEM standard and the manufacturer's instructions always take precedence on site.
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