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Gas Information Sheet 04: Allowable leakage rate for existing standard installations operating at 1.13 kPa

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This gas information sheet provides information about the allowable leakage rate for an existing installation that has been altered, repaired, or extended, which is a requirement under AS/NZS 5601.1, Gas Installations, Part 1: General installations.

There can be no loss of pressure (and no allowable leakage rate) when the installation is a:

  • new natural gas or LPG installation
  • natural gas installation with a metering or operating pressure of 2.75 kPa or above
  • standard gas installation with a volume greater than 30 litres
  • complex gas installation as defined in the Gas Safety Act 1997.

Allowable leakage rates for existing standard gas installations

Testing for leaks

All gas installations must be leak tested before new work can commence. (See AS/NZS 5601.1 Appendix E6, for more information about leak testing.) Gas leaks can be found using a soapy water solution, leak detection fluid, or other suitable leak detection method.

Sometimes, small leaks can be hard to detect, which is often due to a combination of old appliances, worn gas cocks, and weepy pipe joints.

Provided there is no smell of gas, you can consider making an allowable leakage rate assessment after all reasonable efforts have been made to locate and fix a leak.

What is the allowable leakage rate for an existing standard gas installation with a volume less than 30 litres?

The maximum allowable leakage rate, which depends on the pipework’s volume, is measured over a five-minute period.  For example, for an existing standard gas installation with an overall pipework volume of 15 litres, the allowable leakage rate over five minutes can be anything up to 0.35 kPa. Anything more than that and the installation must:

  • have all faults located and rectified, or
  • be otherwise made safe by isolating the faulty appliance or section of piping.

For allowable leakage rates over five minutes, see AS/NZS 5601.1, Table E1, which has been adopted for use in Victoria.

When can leakage rates be determined with a manometer?

You can only determine leakage rates using a manometer (or by observing the meter test dial) when the:

  • existing standard gas installation is supplied through a domestic-size meter (maximum 6 m3 capacity), and
  • meter is located next to the premises.

Carry out the test with all appliances connected.

What is the difference between metering and flowing pressure?

Metering pressure is the pressure of gas as it flows from the meter:

  • Standard metering pressure is 1.13 kPa, which is a nominal figure used for billing purposes. It can vary between 1.13 kPa and 1.3 kPa depending on the amount of gas flowing and any slight regulator setting variations.
  • Flowing pressure is the gas installation pressure with all appliances operating. The flowing pressure in a standard gas installation with a nominal metering pressure of 1.13 kPa should not be less than 1.13 kPa at the inlet to any appliance.

What is the operating (or standing) pressure?

Operating (or standing) pressure is the maximum pressure the installation will be subjected to under normal conditions without any appliances operating. It:

  • is the pressure at which the meter regulator closes off the supply when gas is not flowing (otherwise known as lock-up pressure)
  • should not exceed 1.7 kPa in a standard installation.

Further information

For further information contact Gas Safety Technical Information on 1800 652 563 and select option 3 or email


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