I read that the elimination of pressure in a propane line will destroy the pipe sealing compound at the treads, causing leaks. That is the reason a propane seller will require a leak test if the tank is allowed to run out.
During normal usage, a propane plumbing system is at a constant pressure. This means that as long as the tank has gas and is supplying the system with propane, a constant pressure is exerted on the piping and the pipe joint compound. The pipe joint compound will expand during normal pressurized usage and will retract if the system loses pressure. This loss of gas pressure may cause leaks to form because of the expansion and retraction of the piping compound within the propane plumbing system.
Will allowing the pressure to drop to zero also destroy a pipe joint seal where Teflon tape was used? I am currently using small portable tanks connected to gas logs by a 1/2 steel line where I used Teflon tape on the joints.
Best Answer
I've been a gas fitter for over 20 years and worked with it much of my childhood before that. That is a completely false statement. I think it's just an excuse to get a tech in your house to see if they can generate a sale. You can almost blow with your mouth the amount of pressure that a propane system will see. After the second stage regulator the pressure is commonly 11" water column. Can you blow water up a 12" straw? Probably. Then you can blow more pressure then what's in your piping system. If a leak were to develop after "losing pressure" then it was extremely loose to begin with and wouldn't have passed the original 15 psi pressue test. 15 psi is 420" water column.
What about when the temperature changes in the house? The expansion and contraction of the fittings would be greatly more significant than a 11" pressure drop. What if you bump into the pipe? Also pipe dope is primarily a anti-seize agent not a leak sealant. It does effectively help seal poorly made threaded connections but that's not its job.