Dig a trench from your propane tank to where the new line will connect to the house. Propane tanks should be set away from the house. In some states, this can be as much as 100 feet from any building. This helps to prevent fire hazards due to leaks or emergencies. Dig your trench a minimum of 18 inches deep to ensure pipes will not be damaged by any traffic or future excavations.
Install the pipes from the tank to the installation site. Many states have specific requirements as to type of pipe and how it is protected from corrosion. Metal pipes will need to be protected from corrosion by wrapping with a special protective tape before burying. Another alternative is to sleeve the pipe inside a PVC pipe. Pipe diameter is dependent upon how much propane is required on the service end. The standard size is normally about 3/4 inch.
Install a valve, if desired, and flex lines on each end of your pipe. You will need to use flex line from the tank to your new pipe as well as from the new pipe to the house connection. Hot and cold causes the pipe to shift, and flex line provides the natural give and take to keep fittings tight and leak proof. Flex lines are usually about 3 feet in length maximum.
Turn on the propane and bubble test for leaks before you bury your pipeline. Use one part dish soap to two parts water to check all fittings and connections. Place a few drops of the soapy water onto the fittings. If you see bubbles forming, then you have a leak. Turn off the propane and tighten any loose fittings.
Have the pipe inspected, if required. Many states require new propane service to be inspected before it is buried. If so, have your state inspector review your installation before you bury your pipeline.