Simple plumbing question re: teflon tape

[SPYDERLK]

Two well considered posts in a row.
larry

 

[CFHartman]

I do not disagree with those who say this. i have heard it and read it many times as well. but why then can't we just use a little oil or grease when connecting threaded fittings (other than in potable water systems of course)? if all we really need is a temporary lubricant during tightening and the threads are supposed to seal perfectly against themselves, why doesn't this approach ever seem to work?

Theo

Many times I have used only a lubercant like anti seze on thread espespecially low PSI steam lines.

 

[kenmac]

I do not disagree with those who say this. i have heard it and read it many times as well. but why then can't we just use a little oil or grease when connecting threaded fittings (other than in potable water systems of course)? if all we really need is a temporary lubricant during tightening and the threads are supposed to seal perfectly against themselves, why doesn't this approach ever seem to work?

Theo

Threads aren't perfect so, the lube does seal the imperfections in the threads. Pipe compounds are made up of a different lubricant than just oil.

Same reason you can't or don't use WD 40 or bar chain oil to lubricate a automive engine. Different make lube make up

 

[Egon]

In some types of service threaded connections are not considered secure until they are back welded.

 

[Farmwithjunk]

A few years back, the general contractor I work for built a new building that housed a hydraulics/"fluid power" trade school. As a bonus, once we'd completed the building, the schools founder/owner invited several of us to attend one of his 3 day "short course" classes. It was sponsored by Parker Hannifin. We were taught to use just enough teflon tape to sufficiently lap over, but NOT to use enough to make even two complete wraps. We were told to leave the initial 10% to 15% of the thread uncovered (where thread starts at end of pipe), and to cover the remaining 85% to 90%. Size of pipe determined width of tape used. (ie larger pipe, wider tape)

 

[JDeereman]

In some types of service threaded connections are not considered secure until they are back welded.

Seems to defeat the whole point and purpose of using threaded fittings in the first place, doesn't it? would such a system still meet the plumbing code? are malleable or cast iron fittings still good if back welded?

Theo

 

[Egon]

I doubt these situations would arise in home type plumbing situations.

But they may occur in some situations where explosive/flammable liquids/gases are present.

And the fittings used in these situations are still good after back welding.

 

[patrick_g]

All this teflon talk but... no one mentioned the fact that tapered threads act like a wedge when tightened. Teflon tape lubricates the threads very well so the force required to over tighten the joint may go unnoticed resulting in cracking the female fitting be it brass, iron, steel, or whatever.

If you have much experience with pipe dope then be advised tightening a joint to the same "torque" when using teflon can crack the female fitting. You may not notice the crack (at first) or it may not appear until the joint heat cycles a few times.

My yellow (gas) teflon tape IS thicker. I have installation instructions accompanying equipment that FORBID the use of teflon and void the warranty if it is used. One itsy bitsy piece of teflon in the wrong place is not a good thing for a plasma cutter, for example.

Pat

 

[ray66v]

All this teflon talk but... no one mentioned the fact that tapered threads act like a wedge when tightened. Teflon tape lubricates the threads very well so the force required to over tighten the joint may go unnoticed resulting in cracking the female fitting be it brass, iron, steel, or whatever.

If you have much experience with pipe dope then be advised tightening a joint to the same "torque" when using teflon can crack the female fitting. You may not notice the crack (at first) or it may not appear until the joint heat cycles a few times.

My yellow (gas) teflon tape IS thicker. I have installation instructions accompanying equipment that FORBID the use of teflon and void the warranty if it is used. One itsy bitsy piece of teflon in the wrong place is not a good thing for a plasma cutter, for example.

Pat

Actually, I believe all those points were mentioned in previous posts.

 

[kenmac]

went on a service call where a guy installed his own gas water heater. Said he wasn't getting enough gas to the main burner. He had used teflon tape on the joints. .Some of the tape had broken loose (somehow) & got in the control valve obstructing the gas flow to the main burner. He still came out cheaper than if I would have installed the W.H. Cost him $85.00 for the service call. A water heater install would have cost $450.00 plus the cost of thr W.H.