Pipework & Meters Flashcards
6 cards from real ACS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Pipework & Meters flashcards as text
What is the minimum depth at which a domestic gas service pipe must be buried in a footway (pavement)?
Answer: 375mm
Gas service pipes must be buried at a minimum depth of 375mm in footways and 450mm in roads and driveways to protect them from damage by excavation or surface loading.
What is a 'gas isolation valve' and what are the two main types used in domestic installations?
Answer: A quarter-turn ball valve or lever valve used to isolate individual appliances from the gas supply, and the plug cock used as the Emergency Control Valve
Quarter-turn ball valves (lever valves) isolate individual appliances quickly; plug cocks are commonly used as the ECV; both provide positive isolation of the gas supply.
What information must be marked on a gas meter at a domestic installation?
Answer: The meter serial number, gas transporter's name, index reading units, and maximum continuous flow rate (Qmax)
Gas meters must carry identifying information including the serial number, transporter identity, Qmax (maximum flow rate), and units of measurement to enable accurate billing and engineering assessment.
What is the purpose of a 'gas strainer' installed upstream of a gas meter or regulator?
Answer: To remove solid particles, debris, and scale from the gas supply that could damage the meter or appliance controls
A gas strainer (filter) captures solid contaminants in the gas supply that could damage sensitive meter mechanisms, pressure regulators, or appliance controls, extending their service life.
Under BS 6891, when gas installation pipework has been left open or disturbed, what must be done before restoring the gas supply?
Answer: Cap or plug all open ends, conduct a full tightness test to verify integrity, then purge the air from the installation in accordance with the purging procedure
Open pipework must be sealed, the installation must pass a tightness test, and air must be purged before any appliance is lit — failing to do so risks a dangerous air-gas mixture or undetected leak.
What is the maximum permissible pressure drop in a domestic gas installation during a working pressure test with all appliances on full fire?
Answer: 1 mbar below standing pressure at the appliance, as any greater drop indicates undersized or restricted pipework
BS 6891 and appliance manufacturer data specify that working pressure at the appliance should be within 1 mbar of the required operating pressure — greater drops indicate undersized pipework that must be rectified.