Guide only — not a substitute for IGEM/UP/1B Ed 4 training or the standard itself. The permissible drop for an existing installation is set by the Installation Volume and read from the Ed 4 permissible-limits table for the gas type — calculate IV and enter the value; this tool won't derive it. Any perceptible movement on a new install or a pipework-only retest is a fail. UP/1B scope is IV ≤ 0.035 m³, ≤ 35 mm, ≤ 21 mbar; larger commercial work falls under UP/1A or UP/1.
Purge Volume
IGEM/UP/1B Ed 4
Installation Volume (IV)
— m³
Purge Volume (PV = 1.5 × IV)
— m³
Pipework internal volume using standard internal diameters (steel to BS 1387 medium; copper to BS EN 1057). Edition 4 standardises purge volume as PV = 1.5 × IV for all installations. Fittings are taken as ~10% of the pipework volume. Purge at an adequate rate and confirm with a gas detector at the far outlet; appliance volumes are not included here.
Gas Rate & Heat Input
Metering · Thermal Energy Regs 1996
0.0s
Stop fills the time field
Gas Rate
— m³/h
Standard method: metric — measure the volume used over 120 seconds; imperial — time one full revolution of the test dial. The 1.02264 correction factor is the natural-gas figure set by the Gas (Calculation of Thermal Energy) Regulations 1996; it is set to 1.000 for LPG (edit if a specific factor applies). Gross CV ~39.5 MJ/m³ for UK natural gas, ~95 MJ/m³ for propane — use the actual figure where known. Net heat input uses a gross→net factor of 0.901 (NG) / 0.921 (LPG).
Plant-room Ventilation
BS 6644 · IGEM/UP/10
Low-level (inlet) Free Area
— cm²
High-level (outlet) Free Area
— cm²
Mechanical Air Supply (low level)
— m³/s
High-level Discharge (if not mechanically assisted)
— cm²
Pipe Sizing — Pressure Drop
BS 6891 · IGEM/UP/2
Enter each section's pipe size, length, fittings and the gas rate through it — the tool computes the pressure drop from the BS 6891 discharge data and totals it against the limit. Use the helper to convert appliance kW to m³/h.
Total Pressure Drop
— mbar
Pressure drop is computed by the BS 6891 method — the discharge that gives 1 mbar at that length is scaled by the actual gas rate (drop is taken as linear in rate, which is slightly conservative). Effective length = measured length + fittings (elbow 0.5 m, tee 0.5 m, 90° bend 0.3 m; for 35 mm+ the elbow/tee allowance rises to ~1.0 m — use the extra-length box). Each appliance's drop from the meter outlet must stay within 1 mbar (NG). BS 6891 covers ≤ 35 mm copper / 32 mm steel; larger commercial pipework is IGEM/UP/2. Verify against the standard before sign-off.