MET1 revision guide: gas meters, regulators and the ECV

What MET1 covers

Domestic-sized meter installations: diaphragm meters such as the U6 and G4, electronic and smart equivalents such as the E6, meter boxes and compartments, regulators, the emergency control valve and the connections around them. The module tests whether you can install, exchange, check and leave a meter installation safe — and whether you recognise when someone else has left one unsafe.

Locations, boxes and compartments

• External meter boxes: purpose-made, protected from damage, with the box vented as designed — and never sealed up to keep draughts out.
• Internal locations: accessible, ventilated where required, away from heat and ignition sources, and not in a position that traps escaping gas.
• Compartments and cupboards follow the same principle: a meter must be reachable, readable and safe to work on.
• Protection matters: a meter where cars park, or under a likely impact point, is a siting question before it is anything else.

The emergency control valve

The ECV is the consumer’s means of shutting off the gas in an emergency, so the revision points are all about usability: it must be accessible without tools or keys hidden elsewhere, its handle fitted so the off position is obvious and reached with a simple movement, and it should be labelled with emergency instructions so a member of the public can act. An ECV buried behind boxing, painted solid or missing its label turns up constantly in unsafe-situations questions.

Regulators and seals

The meter regulator holds the installation at its working pressure. Two things matter for revision: the regulator must be the right one, fitted the right way, and its sealing arrangement must be intact — the seal is the transporter’s evidence that nobody has interfered with the pressure setting or stolen gas. A broken or missing seal is not yours to re-crimp: it gets reported to the meter owner, and suspected tampering or theft has its own reporting route.

Bonding and connections

Main equipotential bonding connects to the installation pipework near the meter outlet, before any branch — the commonly taught figure is within 600 mm of the meter outlet, with the clamp accessible and labelled; the current standard and the electrical side of the job give the exact requirement. Meter unions must be accessible, and where the installation uses an insulating joint, it stays in — it is there to keep stray electrical current off the buried supply.

Testing, labels and leaving safe

• Work on the meter installation ends with a tightness test and, where gas has been introduced or displaced, correct purging before appliances are relit.
• Labels and notices: the ECV emergency notice and the meter installation information a stranger would need.
• Smart meters change the technology, not the duties — location, ECV, sealing and tightness principles still apply.
• Record what you did and leave the installation so the next engineer can prove it safe quickly.

Common exam traps

• Treating the ECV and the meter outlet valve as interchangeable in scenario answers.
• Forgetting that the meter and regulator belong to the transporter/meter owner — damage and seals get reported, not improvised.
• Missing the bonding check after meter work.
• Accepting an unventilated, sealed-up meter box because the customer prefers it tidy.
• Quoting a pressure figure without saying where it is measured and under what condition.