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IGEM/UP/1A reference

Source: IGEM/UP/1A Edition 3, Draft for Comment (IGEM/TSP/13/282, 2013). Summary for quick reference; always check the full current standard.

Scope (Section 1, Fig 1)

Strength test, tightness test and direct purge of NG, LPG/air and LPG installations on industrial and commercial premises with MOP up to 60 mbar, diameter up to 150 mm and IV up to 1 m³ (0.5 m³ for LPG). Bigger, higher pressure, or back pressure / DP over 75 mbar: use IGEM/UP/1.

Strength test (Section 5, Table 1)

*The draft's own worked example uses 82.5 mbar here, so check the published edition. New work and extensions: always strength test (pneumatic, with air). Existing: only after repairs that cannot be tested separately or a pressure increase, and only after a risk assessment. Remove parts that STP could damage. Drop over 20%: find the leak with LDF, repair, retest.

Installation volume (6.2, Tables 2 and 3)

IV = meter + pipe + fittings. If fittings are unknown add 10% of pipe volume. Round the total up to 2 significant figures. Rotary or turbine meters: equivalent 1 m of pipe at connection size. Typical meter IV (m³): U6 0.008, U16 0.025, U25 0.052, U40 0.105, U65 0.129, U100 0.270, U160 0.304, E6 0.0024. Unknown hidden pipe: assume the largest size at the longest length.

Tightness test, new work (6.3 to 6.5.3, Tables 4, 5, 7)

Test with air at OP (TTP = OP). Stabilise for TTD or 6 min, whichever is longer. Pass: drop no more than GRM over TTD (0.5 mbar for a water gauge or 1dp electronic, 0.05 mbar for a 2dp electronic).

Roughly 1 minute per 0.03 m³ of NG volume on a water or 1dp gauge (Table 4). Selected rows only.

Tightness test, existing (6.4.2, 6.5.4, Tables 6, 8, 9)

Test with the gas it contains (air if it may hold air). Let-by first: about 50% OP, valve shut, no perceptible rise over the let-by period. Then raise to OP, stabilise TTD or 6 min, watch the drop over TTD. No smell of gas is also required.

Let-by: up to 0.5 m³ 2 min, to 0.8 m³ 3 min, to 1.0 m³ 4 min (Table 8). Max allowed drop (Table 9) depends on IV and the smallest occupied room volume (RV), roughly 0.5 to 4.7 mbar; bigger rooms allow more. Use the lower RV column and round down to 0.5 mbar on a water gauge. Pipework in an inadequately ventilated area: test joints with LDF or a detector, or test that part as new. Let-by on an ECV: call the Gas Emergency Service; on an MIV: tell the MAM.

Appliance connector (6.6)

Up to 0.12 m³ (NG): let-by on the AIV for 2 min, stabilise 2 min, then no perceptible drop over 2 min. "No perceptible movement" means 0.25 mbar or less (0.2 mbar on a 1dp gauge) (4.2.3).

Direct purge (Section 7, Tables 11 and 12)

Tightness test immediately before admitting gas. PV = 1.5 x (pipe + fittings IV) + meter PV + 1.5 x hose volume; diaphragm meter PV = 5 x cyclic volume. Round PV up before timing. Minimum flow by largest pipe (m³/h): 20 mm 0.7, 25 mm 1.0, 32 mm 1.7, 40 mm 2.5, 50 mm 4.5, 80 mm 11, 100 mm 20, 125 mm 30, 150 mm 38 (at least 0.6 m/s). Recommended purge point / hose / flame arrestor (mm): 20-40 pipe use 20/20/20; 50-100 use 25/40/50; 125-150 use 40/50/50. Max purge time (s) = PV x 3600 / flow. End points: air to gas 90% gas; gas to air under 40% LFL (1.8% gas) for NG.

Safety points

• Vent outdoors, at least 2.5 m above ground and 5 m from ignition sources; flame arrestor on the vent; no PE hose.
• No smoking signs, label valves, fire extinguisher at the vent, keep bonds in place.
• Do not exceed MOP when purging; flare heavier than air gases.
• Under 0.035 m³ can be purged into a well ventilated room without hose (Appendix 6).
• Record STP, MOP and results on a certificate.

IGEM/UP/1B reference

Source: public summaries only (no copy of the standard used): IGEM product page and FAQ for IGEM/UP/1B Edition 4 (published March 2026, in force from 1 October 2026, Edition 3 withdrawn 30 September 2026), Installer Online articles on Editions 3 and 4, and trade quick guides (ACS Gas Quick Reference, TomKat IGEM worksheet, gb-gas onsite guide). Summary for quick reference; always check the full current standard.

Scope (Edition 4, clause 2.2, from IGEM summary)

• NG, LPG/air and LPG; NG includes blends with up to 20% hydrogen.
• MOP at the ECV outlet up to 2 bar (NG and LPG/air).
• Pipe nominal bore up to 35 mm (DN32, R1¼).
• Meter badged capacity up to 16 m³/h.
• Installation volume up to 0.035 m³ for an individual dwelling or non-domestic premises.
• Nominal OP up to 21 mbar at the meter outlet and in the section (NG, LPG/air); LPG up to 37 mbar after the final stage regulator.
• Bigger than this: use IGEM/UP/1A or IGEM/UP/1.

Tightness test procedure (NG, from trade guides)

1. Inspect, seal open ends. Appliance isolation valves open, burner taps and pilots off, cooker lids up.
2. Turn off the ECV / AECV / MIV, fit the gauge.
3. Let-by: 7 to 10 mbar, watch for 1 min. No perceptible rise.
4. Raise to 20 to 21 mbar (low pressure supply; 18 to 19 mbar is quoted for medium pressure meters). Stabilise 1 min, re-adjust.
5. Test 2 min. No perceptible movement (0.25 mbar on a water gauge) and no smell of gas = pass.
6. Drop with existing appliances connected: work out IV and compare with the limits below; then isolate appliances and prove the pipework alone with no perceptible movement.
7. Remove the gauge, reseal, restore gas, LDF test the test point, ECV outlet and regulator joints.

Max drop, existing appliances, natural gas

Edition 4 (by installation volume; from ACS and TomKat guides, not checked against the standard):

Edition 3 (by meter, now withdrawn; Installer Online): no meter or E6: 8 mbar (pipe up to 28 mm), 4 mbar (over 28 to 35 mm). Diaphragm under 6 m³/h (U6, G4): 4 mbar / 2.5 mbar. Diaphragm 6 to 16 m³/h (U16): 1 mbar. New work or pipework only: no perceptible movement.

Other fuels, Edition 4 (TomKat guide, unconfirmed): LPG/air up to 0.025 m³ 1.5 mbar, to 0.035 m³ 0.5 mbar. LPG up to 0.0025 m³ 2 mbar, to 0.005 m³ 1 mbar, to 0.010 m³ 0.5 mbar, above that no perceptible movement.

Volumes used

Meter IV (m³): U6 / G4 0.008, U16 / G10 0.025, E6 0.0024. Copper per m: 15 mm 0.00014, 22 mm 0.00032, 28 mm 0.00054, 35 mm 0.00084. Add 10% for fittings if unknown.

Purge (Edition 4)

Always calculate IV, then PV = 1.5 x IV (IGEM FAQ; Edition 3 allowed assumed purge volumes for some small jobs). NG: purge to air up to 0.02 m³ PV, purge to ignition (burner) above 0.02 m³. LPG and LPG/air: purge to ignition. Procedure otherwise unchanged from Edition 3.

Not confirmed here

LPG test pressures, purge procedure detail, E6 specific let-by advice and any Edition 4 change to stabilise or test times are not checked against the standard. Use the published Edition 4.

IGEM/UP/1 reference

Source: IGE/UP/1 Edition 2, Reprint with Amendments, August 2005 (Communication 1716). Summary for quick reference; always check the full current standard (later editions exist).

Scope

Strength test, tightness test and direct purge of industrial and commercial installations; testing up to 16 bar MOP, no MOP limit for purging. In this calculator UP/1 applies when IV is over 1 m³ (or outside UP/1A limits).

Strength test, metallic pipe (Section 4, Table 1)

Max drop: 20% STP pneumatic, 5% hydrostatic. PE has its own rows (for example over 100 to 200 mbar uses 1.75 MOP). Hydrostatic needed if STP is over 10.5 bar (up to 150 mm) or 3.5 bar (over 150 mm). Pneumatic STP over 1 bar needs an exclusion zone (Table 2, about 1 to 8 m by STP and IV). Over 2 bar: check at 350 mbar first, then raise in 10% steps. PE over 350 mbar STP: relax at MOP or less for 3 hours before tightness testing.

Tightness test duration (5.6, Tables 9 and 10)

F1 (Table 10): NG 42 on gas, 67 on air or nitrogen; propane 102 / 221; butane 128 / 305; LPG/air SNG 45 / 60. Round up to the next whole minute. If TTD is over the gauge's maximum (Table 6), split the section or do an extended test (for example 24 h) with temperature and pressure corrections (Appendix 6).

MPLR (5.5)

New work: no movement over GRM. Existing (NG): Type A 0.0014 m³/h, Type B 0.0005 m³/h per m³ of smallest room, Type C 0.03 m³/h. Leak rate = F3 x drop (mbar) x IV / TTD (F3: NG 0.059 on gas, 0.094 on air, Table 11).

Test method (5.7)

• New: valves open against sealed ends; raise slowly (10% steps over 2 bar); stabilise TTD or 15 min, whichever is longer (60 min usually enough for long tests); movement must be under GRM.
• Existing: let-by test at about 50% OP over TTD, no rise over GRM; then stabilise and test as above; if drop is over GRM, calculate leak rate against MPLR.
• Untraceable small leak: only deem safe if no smell, Type A pipe tested to new standard, joints and ground checked with a detector, and the customer agrees in writing.
• Appliance connector up to 0.12 m³: no perceptible movement over 2 min at OP or more.

Direct purge (Section 6, Tables 12 and 13)

Tightness test immediately before admitting gas. PV = 1.5 x (pipe + fittings IV) + meter PV + 1.5 x hose / vent volume; diaphragm meter PV = 5 x cyclic; rotary / turbine PV = 1.5 x equivalent pipe IV. Minimum flow (m³/h) by largest pipe: 20 mm 0.7, 25 mm 1.0, 32 mm 1.7, 40 mm 2.5, 50 mm 4.5, 80 mm 11, 100 mm 20, 125 mm 30, 150 mm 38, 200 mm 79, 250 mm 141, 300 mm 216, 400 mm 473. Over 150 mm, max purge length is limited (for example 500 m at 200 to 600 mm). Recommended purge point / hose / flame arrestor grow with pipe size (Table 12). Max purge time (s) = PV x 3600 / flow. Start testing vent gas after half the purge time. End points for NG: air to gas 90% gas; gas to air 1.8% gas (40% LFL). Incomplete purge: stop and purge with nitrogen (Appendix 8). Propane, butane and LPG/air: nitrogen purge recommended.

Safety points

• Written procedure for all but simple purges; no other work on the section while purging.
• Purge points at every branch end; purge branches in reducing order of size; break up ring mains.
• Vent safely outdoors with flame arrestor, signs, extinguisher and bonds; do not exceed MOP.
• Never let air into the gas network. Record results on a certificate.

Information and sources

Which standard

This calculator picks the standard by installation volume only (meter + pipes + 10% fittings): IV up to and including 1 m³ uses IGEM/UP/1A, over 1 m³ uses IGEM/UP/1. Note: the published UP/1A scope also mentions MOP up to 40 mbar, supply MOP up to 75 mbar and bore up to 150 mm. The page shows a reminder if the pressures are higher, but it does not change the selection. Very small installations (IV up to 0.035 m³, pipe up to 35 mm) may fall under IGEM/UP/1B instead.

Installation volume

IVt = IVm + IVp + IVf. IVf is taken as 10% of IVp when fittings can't be calculated. IVt is rounded up to 2 significant figures. Diaphragm meter IVs: U6 0.008, U16 0.025, U25 0.037, U40 0.067, U65 0.100, U100 0.182, U160 0.304 m³.

Rotary meters: IV taken as 1 m of pipe at the meter connection diameter. The standard's own formula is 0.79 x d² x L using the flange to flange length, so 1 m is on the safe (larger) side for these meters. Connection sizes are Dresser Roots sizes (Dresser codes B4B 2 in, B4C 3 in, B4D 4 in, B4E 6 in, B4F 8 in; 102M 10 in). 9M comes in 3 in and 4 in versions. Sizes can still be changed per job.

Tightness test duration (TTD)

Type A area (inadequately ventilated, used for new work): TTD = GRM x IV x F1.
Type B (adequately ventilated room under 60 m³): TTD = 2.8 x GRM x IV x F1 / RV.
Type C (over 60 m³, external or buried): TTD = 0.047 x GRM x IV x F1.
F1 = 42 natural gas, 67 air or nitrogen. Round up to the next full minute, minimum 2 minutes. If TTD is over the gauge's typical maximum (water / 1dp gauge 30 min, 2dp gauge 15 min, high SG 45 min) use a more sensitive gauge.

MPLR: Type A 0.0014 m³/h, Type B 0.0005 m³/h per m³ room, Type C 0.03 m³/h. New installations: no gauge movement over GRM allowed. Stabilisation: TTD or 15 min, whichever is longer (UP/1 method).

UP/1A existing installations, typical TTD by IV (gas / air): up to 0.15: 2/2; to 0.3: 2/3; to 0.45: 3/5; to 0.6: 4/6; to 0.75: 5/8; to 0.9: 6/9; to 1.0: 6/10 min. Let-by at 50% OP: up to 0.5 m³ 2 min, to 0.8 m³ 3 min, to 1.0 m³ 4 min.

Strength test (pneumatic)

MOP up to 100 mbar: STP = greater of 1.1 x MIP or 2.5 x MOP, stabilise 5 min, STD 5 min.
MOP over 100 mbar to 2 bar: STP = greater of 1.1 x MIP or 1.5 x MOP, stabilise 10 min, STD 5 min.
MOP over 2 bar to 7 bar: STP = greater of 1.1 x MIP or 1.5 x MOP, stabilise 15 min, STD 30 min.
Maximum permitted drop 20% of STP. Hydrostatic test needed where STP would exceed 3.5 bar on pipe over 150 mm, or 10.5 bar on pipe over 25 mm. Typical LP meter installation: MOP 21 to 23 mbar, MIP 75 mbar, so STP 82.5 mbar.

Purge

PV = 1.5 x (IVp + IVf) + meter PV + 1.5 x hose volume. Diaphragm meter PV = 5 x cyclic volume (U6 0.01, U16 0.03, U25 0.05, U40 0.10, U65 0.125, U100 0.285, U160 0.355 m³). Rotary / turbine meter PV = 1.5 x its IV. Hose volume uses the steel pipe volume per metre for the hose bore.

Minimum purge flow by largest nominal pipe size (m³/h): 20 mm 0.7, 25 mm 1.0, 32 mm 1.7, 40 mm 2.5, 50 mm 4.5, 80 mm 11, 100 mm 20, 125 mm 30, 150 mm 38, 200 mm 79, 250 mm 141, 300 mm 216. Sizes not listed use the next larger size (so 65 mm uses 80 mm, 15 mm uses 20 mm). Max purge time = PV x 3600 / flow (seconds). Above 150 mm, IGEM/UP/1 limits purge lengths; check the standard.

Meter only test (no pipework added): IV = meter IV only; purge volume = meter PV + hose. Rotary meters use the flow rate for the meter's connection size. Diaphragm meters use the larger of the meter outlet and the largest pipe for the purge flow rate. Outlet sizes: U6 25 mm, U16 32 mm, U25 and U40 50 mm, U65 and U100 80 mm, U160 100 mm. Manually entered meters with no pipework use the 150 mm rate. The purge size can still be set by hand.

Pipe volumes per metre (m³)

Steel: 15 0.00024, 20 0.00046, 25 0.00064, 32 0.0011, 40 0.0015, 50 0.0024, 65 0.0038, 80 0.0054, 100 0.009, 125 0.014, 150 0.02, 200 0.035, 250 0.053, 300 0.074.
Copper: 15 0.00014, 22 0.00032, 28 0.00054, 35 0.00084, 42 0.0013, 54 0.0021; 67, 76.1 and 108 worked out from the tube bore (marked *).
PE SDR11: 20 0.00019, 25 0.00033, 32 0.00053; bigger sizes and all SDR17 worked out from bore = OD x (1 - 2/SDR) (marked *).

Sources

• IGEM: IGE/UP/1A Edition 2 scope (igem.org.uk resource page) for the UP/1A limits.
• IGEM/UP/1C draft for comment (IGEM/TSP/10/122): Table 5 strength testing, Table 10 purge flow rates, Table 14 meter IV and cyclic volumes, Table 15 pipe volumes, Tables 16 and 17 gauge GRM and F1, TTD = GRM x IV x F1.
• Installer magazine "Nice and tight" (IGE/UP/1 summary): MPLR types A, B, C and TTD formulas.
• RAD Midlands IV and PV calculation sheets: steel pipe volumes, meter IV and PV.
• NICEIC Pocket Guide Gas 2: copper and PE pipe volumes, fittings at 10%.
• heatwizard.co.uk summary of UP/1A existing installation TTD and let-by tables.
• Dresser Roots Series B3 rotary meter data sheet and misl.org / processvalve.com summaries: rotary connection sizes.

This page is a calculator to help with planning. It does not replace the standards, your training, or a site specific procedure.