CCN1 Pipework Installation & Tightness Testing 2 — Questions and Answers
Question 1: What is the purpose of a gas meter bypass?
- It is not a legitimate installation component — a bypass around a gas meter is illegal as it allows gas use without metering (Correct answer)
- It allows gas to continue during meter maintenance
- It is a pressure regulator fitted parallel to the meter
- It is a safety valve that diverts gas during excess pressure events
Correct answer: It is not a legitimate installation component — a bypass around a gas meter is illegal as it allows gas use without metering
There is no legitimate purpose for a bypass around a gas meter in a domestic installation. Creating or using a meter bypass is a criminal offence as it enables theft of gas and creates serious safety risks.
Question 2: What is a 'pressure governor' (regulator) in a domestic gas installation and where is it located?
- A device that reduces the high pressure from the gas main to the lower working pressure (typically 20-21 mbar) required by domestic appliances — located at or in the meter assembly (Correct answer)
- A device inside each individual gas appliance
- A device in the gas main under the road
- A pressure governor is only fitted to commercial installations
Correct answer: A device that reduces the high pressure from the gas main to the lower working pressure (typically 20-21 mbar) required by domestic appliances — located at or in the meter assembly
The pressure governor (regulator) is part of the meter assembly. It reduces the gas supply pressure from the higher distribution main pressure to the lower working pressure (approximately 20-21 mbar) required by domestic appliances.
Question 3: What must a Gas Safe engineer check when installing new gas pipework?
- That it is correctly sized, properly supported, uses approved materials and jointing methods, is tested for tightness, and is correctly identified (Correct answer)
- Only that the pipe reaches the appliance
- Only that the pipe is correctly sized
- That it matches the colour of the existing pipework
Correct answer: That it is correctly sized, properly supported, uses approved materials and jointing methods, is tested for tightness, and is correctly identified
New pipework installation requires correct sizing, proper mechanical support at specified intervals, use of approved materials and jointing methods, a tightness test of the completed pipework, and correct identification (labelling or marking).
Question 4: What is the correct jointing method for copper gas pipework?
- Compression fittings or capillary (solder) fittings approved for gas use — never push-fit plastic fittings (Correct answer)
- Only push-fit fittings approved for water can also be used for gas
- Adhesive (solvent weld) jointing is the preferred method
- Any plumbing jointing method is acceptable for gas copper pipe
Correct answer: Compression fittings or capillary (solder) fittings approved for gas use — never push-fit plastic fittings
Copper gas pipework may be joined with compression fittings or capillary solder fittings that are approved for gas use. Push-fit plastic fittings approved for water are NOT suitable for gas. Approved fittings must carry the relevant British Standard marking.
Question 5: At what intervals must copper gas pipework be supported (clipped) in a domestic installation?
- Every 1.2 metres for horizontal runs and every 1.8 metres for vertical runs (15 mm copper) — per BS 6891 (Correct answer)
- Every 3 metres regardless of pipe size or orientation
- Only at changes of direction
- Support intervals are at the installer's discretion
Correct answer: Every 1.2 metres for horizontal runs and every 1.8 metres for vertical runs (15 mm copper) — per BS 6891
BS 6891 specifies support intervals for domestic gas installations. For 15 mm copper pipe, supports are required at maximum 1.2 m intervals on horizontal runs and 1.8 m on vertical runs. Correct support prevents sagging and joint stress.
Question 6: What is a CSST (Corrugated Stainless Steel Tubing) and what special installation consideration applies?
- A flexible stainless steel gas pipework system — requires specific bonding and must be installed in accordance with the manufacturer's instructions to prevent static discharge ignition (Correct answer)
- A type of rigid steel pipework used in commercial installations only
- A type of pipework only used for LPG systems
- CSST has no special considerations compared to copper
Correct answer: A flexible stainless steel gas pipework system — requires specific bonding and must be installed in accordance with the manufacturer's instructions to prevent static discharge ignition
CSST is a flexible stainless steel gas piping system. It requires specific bonding (electrical earthing) to prevent static electricity accumulation, which could in extreme cases cause ignition. Manufacturer's installation instructions must be followed precisely.
CCN1 Pipework Installation & Tightness Testing 2
What is the purpose of a gas meter bypass?