There are three spots where gas leaks are usually found in copper gas pipe: gas valves, unions and flare fittings.
Methods to Find Leaks
There are three methods for finding the gas leak in the copper gas pipe.
Check the flare fittings, unions and gas valves with a combustible gas detector. It can be adjusted to detect lower levels of leaking gas.
Check for stains on the copper pipes.
Use dish soap or a gas leak detection solution to find the leak.
To use the combustible gas detector run it along all of the pipes. It makes a clicking sound when you are near the leak enabling you to find the exact location. If you see black stains on the copper tubing that could signify a protracted leak. Mix six drops of dish soap in 1 cup of water to make a solution. Smear it on all of the gas pipe's joints and connections. Allow two minutes for bubbles to form where the soapy water was applied.
Many gas technicians use the soap method or a gas leak detection solution, which also bubbles where a pipe is leaking. A big leak can push the solution away prior to bubbles forming. Don't forget to test the seams of your water heater's valve.