Though copper supply pipes are soldered into place and PVC/ABS/CPVC joints are permanently cemented, gas pipe sections are threaded and tightened into place. If the gas pipe is screwed too tightly, it can break the threads on the gas pipe, as well as the female threads on the gas pipe coupling. Loosening the gas pipe is carried out with a pipe wrench, and a soapy water test is then conducted to ensure that no gas is leaking from the coupling joints.
Turn off the gas supply at the gas meter. Loosen and remove the flexible gas supply hose connected to the gas shutoff valve. Do this by placing a crescent wrench around the hose nut attached to the shutoff valve, and turning the wrench handle counterclockwise (the shutoff valve will be attached to the end of the gas supply line).
Place a pipe wrench around the shutoff valve's body, and turn the wrench counterclockwise to remove the valve from the gas pipe. Place the wrench around the first gas pipe section, and turn it counterclockwise to remove it from the first connecting coupling. Place the wrench around the connecting coupling, turning it counterclockwise to remove the coupling. Continue in like fashion until the over-tightened gas pipe end is reached.
Place the wrench around the over-tightened pipe, and turn the wrench counterclockwise to fully remove the pipe -- the gas pipe must not merely be loosened, as the threading compound applied to the pipe thread now may not adequately seal the pipe to the coupling. Brush the threading compound around the gas pipe thread, and screw it by hand into the existing coupling. Place the wrench around the pipe near the coupling, and turn the wrench clockwise to tighten the pipe in place. Do not over-tighten the pipe, but after fully hand-tightening the pipe, use the wrench to complete no more than two full rotations.
Reinstall all pipe sections in like fashion by first applying threading compound to the pipe threads, and tightening the pipes (and end shutoff valve) into place with the wrench. Wrap yellow sealing tape twice clockwise around the thread on the side/end of the shutoff valve, and screw on the supply hose nut by hand. Tighten the nut in place with the crescent wrench. Turn the gas on at the gas meter.
Mix some water and soap to create a soapy solution. Pour it into a spray bottle. Spray the solution all around the pipe couplings that have been removed and reinstalled. Wait for the solution to settle, and look for bubbles indicating that gas is escaping from the coupling joints. If this is the case, the pipe has to be tightened to the coupling one-quarter turn until the bubbles cease.
Call a city inspector after the work has been completed to inspect the gas line for any leaks.