Around here, nothing but a yellow flex poly tubing is acceptable. Has to be the
right plastic so gas will not weep through and has to be yellow or orange so
people will reconize it when they find it accidently. Uses special conectors
with glads to prevent leaks. Years ago, I used black poly tubing and every time
my property flooded, I could fine the location of the buried gas line from the
tiny bubbles in the floodwater.