Fault guide
Gas Proving System Fault
A gas proving system pressure-tests the kitchen pipework before it lets gas through. A proving fault means the test failed — most often an appliance tap left open, but sometimes a genuine leak or a passing valve seat, so it must never be reset blindly.
- Failed proof is a safety result, not a nuisance trip
- Tightness testing and leak location before any reset
- Proving panels, valves and switches repaired or replaced
System architecture
How proving works
- Ventilation is proven and the operator presses start
- The panel opens a small proving valve to pressurise the appliance pipework
- A pressure switch checks the pipework holds pressure for a set period
- If the test passes, the main solenoid valve opens and the gas-on lamp lights
- If pressure bleeds away, the panel locks out and keeps the gas closed
Why the proof fails
| Cause | Detail | Action |
|---|---|---|
| Appliance tap or hose left open | Most common cause by far | Close all appliance taps and reconnect hoses, then retest |
| Genuine pipework or appliance leak | Pressure bleeds away every attempt | Tightness test and leak location — do not reset |
| Passing main valve seat | Pipework cannot be isolated for the test | Replace the solenoid valve |
| Proving pressure switch drifted | Fails at pressures that should pass | Recalibrate or replace the switch |
| Proving valve stuck or blocked | Pipework never pressurises | Repair or replace the proving valve |
| Test period set wrongly | Marginal fails on a large installation | Recommission the panel settings |
What we do on site
- Read the panel lockout code and test sequence
- Isolate and tightness test the carcass to the relevant procedure
- Locate and repair leaks, or replace passing valves
- Recalibrate the proving pressure switch and test timings
- Prove, reset, functionally test and certify the whole system
If you can smell gas
- Turn off the gas at the emergency control valve and press the emergency stop button
- Do not switch anything electrical on or off, and do not use naked flames
- Open doors and windows, evacuate and keep people clear
- Call the National Gas Emergency Service on 0800 111 999
- Only then call us to make the installation safe and return it to service
Frequently asked questions
Can a proving lockout be reset without testing?
No. The lockout is telling you the pipework did not hold pressure. Resetting without investigation risks releasing gas into leaking pipework.
Why does it fail first thing in the morning only?
Usually because appliance taps or quick-release hoses were left open overnight. Cold pipework and a marginal test period can also contribute.
Do all kitchens need proving as well as interlock?
Not all. Proving is commonly specified for schools, care homes and other higher-risk or unsupervised premises; the risk assessment and specification decide.
Do you supply proving panels?
Yes — Merlin, Medem, Black Teknigas and equivalent proving panels, supplied, fitted and commissioned.
Related guides
Gas Proving Systems
Pressure proving panels, operating sequences and commissioning.
Gas Safety Control Panels
Interlock and proving panels, indicators and diagnostic codes.
Solenoid Valve Faults
Valve won't open, keeps closing, buzzing or leaking by.
Interlock Won't Reset
Reset sequence, latched faults and why the panel keeps dropping out.
Emergency Interlock Engineer
24/7 UK call-out when the kitchen has no gas and service is on.
Commercial Kitchen Gas Safety
Ventilation interlock, airflow proving and CP42 compliance.
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