What the test is

After a repair or new installation, the gas piping is closed off from the meter and the appliances, then pressurized, usually with air, and connected to a gauge. The contractor records the reading and watches it over a set time. If nothing escapes, the needle does not move.

Test pressure and duration are set by code and, where a permit is involved, by what the city's inspector requires. That is why the details vary from job to job. What does not vary is the principle: no gas goes back into piping that has not held its test.

A typical sequence

Before the test
All new joints are made up and appliance valves are closed or the appliances are disconnected and capped.
Pressurize
The piping is charged to the test pressure and a gauge is attached where it can be read.
Hold
The reading is noted and the system is left alone for the required time.
Inspection
Where a permit applies, the inspector may want to see the gauge holding before walls are closed.
Pass
Test pressure is released, appliances are reconnected, and joints at the appliances are checked with leak solution.
Restore
Gas is turned back on, air is purged from the lines, and pilots and burners are lit and checked.

Reading the result

  • IfThe needle holds steady for the full timeThenThe piping passed; move on to reconnecting appliances.
  • IfThe needle drops slowlyThenThere is a small leak. Isolate sections and check joints with leak solution.
  • IfThe needle drops fastThenA large leak or an open line; check for missed caps and open valves first.
  • IfThe reading moves up or down with temperatureThenSun on an outdoor line can shift readings; the contractor should account for it before calling it a pass.

Jobs that should end with a pressure test

Why the test cannot be skipped

A new threaded joint can look perfect and still weep. A CSST fitting can be one turn short. A cap on an abandoned line can be loose. None of these show up by looking, and some will not smell right away either. The gauge catches them before anyone is living with the result, which is why a test is part of the job rather than an extra.

Common questions

Is a leak solution check the same as a pressure test?

No. Leak solution finds a leak at a joint you can see. A pressure test proves the whole section of piping is tight, including joints you cannot see.

Will the inspector do the test?

Usually the contractor sets up the test and the inspector observes it where a permit is involved. Check with the city on how it handles your job.

How long does it take?

It depends on code and the inspector's requirements. Plan for the gas to stay off until the test passes and appliances are relit.

General information for Fullerton, not a quote or professional advice. In an emergency, call 911.