Teflon Tape + Gas?

[71_Bronco 1,072]

On my Lawn Ranger, I am took apart the glass sediment bowl (to clean), and am re-running all new fuel lines.

 

Where things thread together (tank to bowl, bowl to nipple), will Teflon tape be okay to use on the threads to seal? Or should I just crank them down since they are tapered pipe threads and hope for the best? Or perhaps a liquid like blue loc-tite?

 

Also need to make an extension on my oil drain pipe (again with steel pipe threads). Just crank down on those too? Or will engine oil be a little more forgiving on Teflon tape?

[ebinmaine 67,695]

White colored regular old Teflon tape is not compatible with gasoline.

 

There is a yellow Teflon tape that is compatible with gas like barbecue or natural. But I have a roll at the house that specifically says not to use it with gasoline.

 

If I'm using an NPT thread I normally just put them together dry using all new fittings  wherever possible... and very very rarely do I have a leak of any kind. 

 

I know there are sealants on the market specifically designed for this. I'll be curious to see what others say.

 

[953 nut 55,329]

A tiny bit of Teflon tape or any amount of other "sealant" that gets into the fuel system WILL find its way into your carburetor and cause problems. Clean NPT threads with a drop of oil  will tighten up leak-proof.

Edited February 5, 2021 by 953 nut

[DennisThornton 4,769]

For years I thought Teflon tape was to goto for every threaded fitting.  Then I learned that the yellow should be used for propane.  After selling propane heaters and dealing with fuel suppliers I've just about dropped using Teflon tape.  I've had new brass fittings with white teflon leak water.  Multiple ones on the same job.  I've used lots of brass with no sealant and not had leaks.  Most pros and propane dealers use Blue Monster or a teflon paste rated for what they are trying to contain.  Unless it's brutal cold I use paste but if it gets so stiff that it's just not usable I use Blue Monster.  I found this online.  I didn't know all this...

• White: used on NPT threads up to 3/8 inch
• Yellow: used on NPT threads 1/2 inch to 2 inch, often labeled "gas tape"
• Pink: used on NPT threads 1/2 inch to 2 inch, safe for potable water
• Green: oil-free PTFE used on oxygen lines and some specific medical gasses
• Gray: contains nickel, anti-seizing, anti-galling and anti-corrosion, used for stainless pipes
• Copper: contains copper granules and is certified as a thread lubricant but not a sealer

 

 

Thread seal tape - Wikipedia

 

[71_Bronco 1,072]

Thanks guys, I kinda figured the tapered NPT threads would "self seal" when tightened down far enough, but wasn't 100% sure.

[RandyLittrell 3,884]

3 minutes ago, 71_Bronco said:

Thanks guys, I kinda figured the tapered NPT threads would "self seal" when tightened down far enough, but wasn't 100% sure.

 

While doing my water heater this weekend, some of the guys here explained that the pipe dope used on npt threads are really just a lube that helps you tighten down the threads till they seal. 

 

 

 

Randy

Edited February 4, 2021 by RandyLittrell

[Greentored 3,216]

Gotta agree with all of the above, and at the same time, was using the white teflon for decades and never had an issue, right up til someone 'educated' me on the white vs yellow tape.

If the threads are good and clean, they should, in theory, not require any sealer.  

A quick trip round the threads with some yellow is cheap peace of mind

 

 

 

Edited February 4, 2021 by Greentored

[WHX?? 48,834]

I use some sort of pipe dope on all my npt threads large or small. I have 6 or 7 different types on loan from work. Salesmen drop off sample bottles and some how they find their way in my lunch bucket... 

In a perfect world with perfect threads might not be needed but we all know about a perfect world. 

1 hour ago, 953 nut said:

Teflon tape or any amount of other "sealant" that gets into the fuel system

All of my install manuals and the mechanical engineering standards say leave the first two threads bare to keep this from happening. 

 

My personal fav..... 

 

Highside Chemicals · Leak Lock

[rmaynard 15,519]

I have been using this for years. Works on air, water, and fuels.

 

[oilwell1415 563]

Good luck getting the threads to seal without anything on them.  I've had pipes that I've had to torque so tight that they collapsed under the pressure of the wrench.  In theory you shouldn't use teflon tape with gasoline, but I've never had any issues with it.  Just make sure you leave a few threads clean at the end so that small slivers of teflon don't come off the end.  That's what gets in the carb and messes things up.

[WHX?? 48,834]

What do you use Plunger? @JCM

[Pollack Pete 2,273]

I worked as a pipefitter in a chemical plant for 40 yrs.We used white teflon tape on ALL threaded fittings.Carbon steel,stainless steel,brass,PVC..Everything from 1/8 inch up to and including 3 inch threaded pipe. We never trusted bare tapered pipe threads to seal.Because..........they hardly ever did.Like others have said.Leave the first thread or two bare.

[DennisThornton 4,769]

45 minutes ago, rmaynard said:

I have been using this for years. Works on air, water, and fuels.

 

I'm a fan of Rectorseal but they make several so be sure to check for your needs, both the pipe material and what's in the pipe.  #5 is a favorite of mine.  Note that it is NOT for O2.

RectorSeal® No. 5® is recommended for pipe carrying:

Acids, Dilute Gasohol (unleaded Gasoline and 10% Alcohol) Natural Gas
Air, Compressed Heating oils Nitrogen, Gaseous
Ammonia- Gaseous, Liquid Helium, Gaseous Petroleum Solvents
Aliphatic Solvents Hydraulic Oils Soap, Liquid
Caustic, Dilute Hydrogen, Gaseous Steam
Cutting Oils (Low Aromatic) Inert Gases Vegetable Oils
Diesel Fuel Oil Kerosene Water (Hot or Cold)
Freons Liquified Petroleum Gases (Butane, Propane,
Mixtures)
Gasoline (Leaded Unleaded) Mineral oils

Not recommended for oxygen
 

[DennisThornton 4,769]

1 hour ago, RandyLittrell said:

 

While doing my water heater this weekend, some of the guys here explained that the pipe dope used on npt threads are really just a lube that helps you tighten down the threads till they seal. 

 

 

 

Randy

Both Teflon and sealants act as lubes to enable more threads in contact.  I've counted the number of turns with and without and I'll often get 2 more threads with teflon or sealant.  Brass deforms and seals better than cast and other metals and I have at times not used sealants on new brass fittings.  Your mileage may vary.  But I'd never expect cast or other metals to seal on their own.

[lynnmor 7,315]

See those little flats at the tip of the external threads and the root of the internal threads?  What do you think will fill those gaps?  Yes, if tightened enough they might conform.

 

[ACman 7,618]

I was taught by my dad many many years ago brass to brass you shouldn’t need anything on the threads . He also taught me you need to be careful with Teflon tape as you could actually tighten it too tight and crack the fitting which I’ve had done  . As a plumber and a hvac installer I’ve installed miles of black pipe from 1/8’ to 4”s . I wouldn’t even think about putting any black pipe , copper or pvc together without some type of thread sealant . I’d use a couple wraps of tape (white or yellow depending on use) and pipe dope like Tru-Blu leaving a couple expose threads on the end like others have stated . If all possible I’d like to let it setup for 24hrs before a pressure test especially if we had to use Chinese fittings . 
 

@71_Bronco it’s just my  I’d just use some pipe dope compatible with gasoline keep it away from the ends of the thread and don’t over tighten .

[rmaynard 15,519]

Chinese SAE threads are sometimes different than American SAE threads. I found that out on some Chinese carburetors that were supposedly built to SAE specs.

[DennisThornton 4,769]

1 hour ago, ACman said:

I was taught by my dad many many years ago brass to brass you shouldn’t need anything on the threads . He also taught me you need to be careful with Teflon tape as you could actually tighten it too tight and crack the fitting which I’ve had done  . As a plumber and a hvac installer I’ve installed miles of black pipe from 1/8’ to 4”s . I wouldn’t even think about putting any black pipe , copper or pvc together without some type of thread sealant . I’d use a couple wraps of tape (white or yellow depending on use) and pipe dope like Tru-Blu leaving a couple expose threads on the end like others have stated . If all possible I’d like to let it setup for 24hrs before a pressure test especially if we had to use Chinese fittings . 
 

@71_Bronco it’s just my  I’d just use some pipe dope compatible with gasoline keep it away from the ends of the thread and don’t over tighten .

Well said.  Can't comment on the Chinese fittings and I never could wait for 24 hrs on any pipe job.  I don't see where that would help with tape or where another 1/2 on sealant would need time either.  

 

And yes, there is a danger to Teflon tape for the newcomer who has been tightening as tight as possible.  Not sure how to explain that to a newcomer either.  Maybe snug and then another 1/2 to full turn?

[WHX?? 48,834]

Jeff also didn't change out those old dies that were in his pipe threader like his dad told him too and now he's got some bad threads. To make matters worse he dropped that nipple on the floor then run it over with the track chair. Now he really may have some messed up threads but if he uses a good quality pipe dope he'll be ok. 

[oilwell1415 563]

1 hour ago, DennisThornton said:

And yes, there is a danger to Teflon tape for the newcomer who has been tightening as tight as possible.  Not sure how to explain that to a newcomer either.  Maybe snug and then another 1/2 to full turn?

My solution when I would take on a mechanic's apprentice back in my mechanic days my solution was to hand them a box of nuts and bolts and a piece of steel plate with holes drilled in it.  I clamped the piece of plate in a vice and told them to put a bolt in each hole, tighten the nut until they were scared, then give it another 1/4 turn.  If they broke a bolt, they had to put another one in and tighten it again.  Once they thought everything was tight I'd check their work with a torque wrench.  A few repetitions of this and they were usually pretty solid on fastener torque.

[DennisThornton 4,769]

1 hour ago, oilwell1415 said:

My solution when I would take on a mechanic's apprentice back in my mechanic days my solution was to hand them a box of nuts and bolts and a piece of steel plate with holes drilled in it.  I clamped the piece of plate in a vice and told them to put a bolt in each hole, tighten the nut until they were scared, then give it another 1/4 turn.  If they broke a bolt, they had to put another one in and tighten it again.  Once they thought everything was tight I'd check their work with a torque wrench.  A few repetitions of this and they were usually pretty solid on fastener torque.

Yep, by then they had some experience.  I told a tech that was having problems with flares to just make several in the shop.  He was afraid of breaking them, spitting the nuts and the flare itself.  So fine!   Practice!  Not in the customer's work but ours in our shop. 
Wasn't long before he got all he needed to be confident.