Pipework Installation & Tightness Testing Flashcards

What does a gas tightness test confirm?

Answer: That the gas installation pipework contains no leaks — confirmed by applying a test pressure and observing for pressure drop

A gas tightness test applies a test pressure to the pipework and monitors for any pressure drop over a specified period. No pressure drop confirms the installation is gas-tight and free from leaks.

What test pressure is used for a domestic gas installation tightness test?

Answer: Twice the operating pressure (typically around 20 mbar for natural gas) or a minimum of 20 mbar whichever is greater

For domestic installations operating at low pressure (typically around 20 mbar), tightness testing is carried out at approximately twice the operating pressure — a minimum of 20 mbar. The specific pressure depends on the type of installation.

What is the standard gas tightness test procedure for a domestic installation?

Answer: Isolate appliances, apply test pressure, allow to stabilise, record pressure, wait specified time, record final pressure and compare

The standard tightness test involves isolating all appliances, applying the correct test pressure, allowing stabilisation for the specified period, recording the starting pressure, waiting the required time, and recording the final pressure to identify any drop.

What action must be taken if a tightness test reveals a pressure drop?

Answer: Trace and locate the leak(s), repair, then re-test to confirm tightness before proceeding with any gas work or restoring supply

Any pressure drop during a tightness test indicates a leak. The leak must be traced (using suitable leak detection fluid or an electronic gas detector), repaired, and the tightness test repeated to confirm the installation is gas-tight.

What material must NOT be used for gas pipework installations in the UK?

Answer: Lead — lead pipework is prohibited for gas installations due to its toxicity and poor joint integrity

Lead pipework is completely prohibited for gas installations in the UK. Materials approved for gas pipework include copper, carbon steel, and approved flexible hoses. Each must be joined using appropriate approved methods.

What pipe sizing consideration is critical to ensure correct gas appliance operation?

Answer: The pipe must be sized to deliver the required gas flow rate (volume) without excessive pressure drop — undersized pipes starve appliances of gas

Gas pipes must be sized to deliver adequate gas volume to all appliances simultaneously at the required pressure. Undersized pipes cause excessive pressure drop, starving appliances of gas and causing incomplete combustion.