Pipework and meter
Choose each pipe size, enter the length and select the meter.
Reference values and calculation notes
Choose the actual pipe material and nominal size, then enter its measured length. The reference volume per metre is filled in automatically. Add every run in the section being tested; use a verified manufacturer value for unlisted pipework. STS must check these preset reference values against its final licensed Edition 4 copy before live use.
Reference values and calculation notes
The metric/imperial choice describes the meter register. A listed meter fills in its internal capacity in m³ regardless of the register type. For any other meter use verified manufacturer data in m³, never the cumulative consumption reading. Where actual valves and fittings volume is known, enter that value. Otherwise, the 10% fallback is applied to the calculated pipework volume. The selected amount is added to pipe and meter volumes. Select “No meter” when excluded and enter 0.
Test setup
Confirm the installation and the test you are carrying out.
Which installations does this cover?
This STS assistant is configured for domestic dwellings with installation volume no greater than 0.035 m³. IGEM/UP/1B itself may cover other qualifying installations, but this tool does not assess them. The engineer must confirm pressure, pipe bore, meter capacity, installation volume and all other scope conditions against the full standard.
Readings and checks
Record observations from the prescribed physical test.
Your test at a glance
Installation: Complete the installation details.
What is allowed? Complete the test setup.
Your pressure drop: Enter the gauge readings.
Your next action: Complete the installation and setup.
Follow the test step by step
- Enter the installation details and confirm the scope. Select the fuel and whether existing appliances are connected, only new appliances are connected, or you are testing pipework only.
- Carry out the physical checks and prescribed timed test. Record the readings and actual gauge movement.
- Follow “Your next action”. A permissible drop with existing appliances is only the first check; any perceptible drop needs an appliance-isolation pipework retest with no perceptible movement.
- Complete the reinstatement, LDF and no-smell checks. Review the overall result and save your working note.
This guide supports a competent engineer using the full current controlled procedure. A phone cannot measure the gas installation or confirm it is safe.
Before the timed test
Confirm the checks required for this arrangement using the controlled procedure.
On-site test helper
Guided test timer
One stage at a time. Set up the gauge and valve as prescribed before you press Start.
- Let-by · 1 min
- Stabilise · 1 min
- Tightness · 2 min
Record gauge readings
Enter the readings observed during each stage. The pressure drop is calculated from the tightness readings; gauge movement remains your observation.
Enter all four readings to document the test stages.
Audible warning
Sound muted. On-screen alerts remain active.
Enable sound on this device and use Test sound before relying on it. Keep GasAssist open and visible. Phone volume, silent settings and browser restrictions can affect playback; always read the on-screen result.
Complete the overall test outcome
Edition 4 limits and completion procedure
Permissible pressure drops depend on total installation volume and fuel, not meter type. The meter contributes its internal volume. An allowance applies only with existing appliances connected and no reported smell of gas.
For natural gas: up to 0.005 m³ → 8 mbar; over 0.005 to 0.010 m³ → 4 mbar; over 0.010 to 0.015 m³ → 2.5 mbar; over 0.015 to 0.035 m³ → 1 mbar.
Any perceptible drop within the applicable allowance requires appliance isolation and a pipework/meter retest showing no perceptible movement. If an appliance cannot be isolated, leave it connected and apply no perceptible movement. A drop above the allowance fails: trace and repair the escape or make safe under the applicable procedure.
New installations, tests with only new appliances, and pipework-only tests require no perceptible movement. This is a gauge criterion: maximum 0.25 mbar for a water or suitable electronic gauge, or 0.2 mbar for an electronic gauge displaying one decimal place. The engineer must confirm the actual observation; the app does not infer it from rounded readings.
Guidance checked against Gas Safe Register ISU 133 Edition 2 (15 April 2026) and its May 2026 technical explanation. Use the full current controlled IGEM/UP/1B Edition 4 procedure. A pass shown here records the entered evidence and remains an engineer aid.
Use the procedure and timings in STS’s controlled copy of the standard. A 0.25 mbar reading on a water or suitable digital gauge, or 0.2 mbar on a one-decimal digital gauge, can count as “no perceptible movement” under ISU 133 Edition 2; the engineer must assess the instrument and actual movement. This form does not infer gauge movement from a number.
Review the calculation
Check the inputs and conditional guidance before saving your working note.
A satisfactory tightness test is required immediately before admitting fuel gas for purging. Maintain good ventilation, prevent gas accumulation and control ignition sources except the intended burner ignition. Keep the purge area attended and follow the complete procedure, including every branch and final appliance checks.
Method threshold uses installation volume, before × 1.5. Quantity alone does not authorise a purge. Follow the applicable current purging procedure and its precautions.
Prototype for STS review · Reference values require verification before live use.