Old plumber told me to never use Teflon tape on gas fittings - I learned why the hard way

So my uncle who's been doing commercial work since the 80s kept saying tape is for water, gas needs dope. I figured he was just old school and ignored him on a 4 inch gas line job last month. Had a leak at the first fitting I tested. Redid it with pipe dope and it sealed up perfect. 45 minutes of extra work for nothing. Has anyone else had a gas fitting hold with tape for a while or am I just lucky it failed right away?

2 comments

2 Comments

king.lisa1mo ago

...and then I had to cut the whole thing out and start over because the tape let go at the second joint too. I feel your pain, man. My dad told me the same thing - gas gets dope, water gets tape - and I thought he was being dramatic. Three separate leaks later, I finally gave up and used the dope. Every single one sealed right away. I don't know why tape doesn't hold on gas, maybe it's the pressure or the way the gas eats at the tape over time. Point is, I'll never touch tape for gas again. You got lucky it failed quick, trust me.

river1901mo ago

Gas gets dope, water gets tape" - that's one of those rules that's true way more often than people want to admit. It's like the whole idea of using the right tool for the job but applied to everyday stuff most of us don't think twice about. I've noticed that pattern everywhere, not just plumbing. People try to force one solution to work in every situation and then get surprised when it fails. Tape works great for water because it's designed to handle that kind of constant pressure and moisture. But gas is different, it has compounds that break down the tape over time plus it's under higher pressure usually. Same reason you wouldn't use a butter knife to screw in a lightbulb, it's just not what it was made for.