MET1 revision notes
Meters and the emergency control valve — installation, ventilation and tightness.
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BS 6400: Meter Housings, Regulators & ECV Access
- Electrical Equipotential Bonding on Gas installationsWhere main protective bonding connects at internal and external gas meters, what it does, and what to do if you find it missing.
- Gas meter and emergency control valve (diagram)The order of parts at a domestic gas meter, from service pipe to appliances, what each one does, and why the ECV must stay reachable.
- Gas meter controls: ECV and meter ventilationThe ECV rules, why every gas meter position must be ventilated, where a meter must not go, and the checks after meter work.
- Meter boxes: protection, ventilation and accessWhat an external gas meter box is for, why its vents must stay clear, and the box faults to spot and put right.
- Meter installation and the emergency control valveHow to pick out the ECV, the handover checks that let a user shut the gas off unaided, and the faults that defeat it.
Emergency Control Valve and Meter Regulator
- Emergency control valve: access, handle and noticeWhat the ECV must give a user: reach, a fixed handle, a notice, an AECV where needed, and the safe way to use it if you smell gas.
- Regulators and standing pressure: what good looks likeWhat the meter regulator does, the natural-gas pressures to know (21, 19 to 23 and 1 mbar), lock-up versus creep, and the seal, breather and OPSO.
Meter Location, Protection and Tightness Testing
- Let-by and tightness test sequence (domestic)The order of a domestic tightness test after meter work: set-up, let-by, stabilisation, the timed test, the Edition 4 result and what to do with a loss.
- Meter and gas testing terms glossaryPlain definitions of the meter, pressure, testing and purging terms in MET1, with the formulas for gas rate, heat input and purge volume.
- Purging gas after meter or pipework workWhy gas pipework is purged after meter or pipework work, how to size the purge (PV = 1.5 × IV) and the order of checks around it.
- Where a gas meter can and cannot be locatedAcceptable and unsuitable gas meter positions: access to the ECV, ventilation, separation from electrics, heat and damage, and escape routes.
Primary Meter Types & Components
Read a gas meter installation as a complete arrangement
MET1 revision brings the meter, regulator, emergency control and installation pipework together. When a question gives a pressure reading, name the measurement point and whether gas is flowing. Those details determine what the reading can establish.
Follow the MET1 guide for the installation checks and the gas-rate calculation guide for timed meter readings. Use the gas pipe-sizing worksheet when revising the downstream appliance load; calculating demand does not establish the condition of the meter or regulator.
In-depth guides for this module
Longer walkthroughs that sit alongside the revision notes.
MET1 revision guide: gas meters, regulators and the ECV
MET1 is about the meter installation itself: location, the ECV, regulator, seals, labels and leaving the installation safe.
BS 6891 gas pipe sizing explained: load, length and pressure drop
Gas pipe size is not chosen from boiler kW alone: each section needs its downstream load, route resistance, fuel, material and pressure-loss check.
More Gas modules
Every module has its own revision notes and question bank.