Per ASTM (American Society of Testing & Materials) Standards we must use a thread sealant on all NPT (National Pipe Taper) Threads & fittings. The type of thread sealant is selected for compatibility with the material that the pipe will be conveying. In residential service the use of NPT joints is normally limited to water, natural gas, propane gas, #1 & #2 heating oils and occasionally low pressure steam, refrigerants or high-pressure air in a shop compressor system.

TEFLON TAPE:

When PTFE (Teflon) tape first became available they only made it in the common single density type, which we commonly find in the hardware and home supply stores. Later they began making a double density version, which was twice as thick. Many state and local codes then adopted the double density type as mandatory when making connections for natural gas however since both products were the same color (white) it was difficult for inspectors to be sure which product had been used. PTFE tape is now made in numerous varieties and they have issued a color standard to determine which type should be used.

WHITE-Single density- should only be used on NPT threads up to 3/8 inch.
YELLOW- Double Density- yellow double density is often labeled as "Gas type"
RED-Triple Density: (Note-the container is red but the tape itself appears as a pale pink color). Presently required on all joints " diameter or greater.
GREEN- Oil Free PTFE tape- Required for use on all lines conveying oxygen (I.E. Âmedical oxygen or welding oxygen lines).
COPPER COLOR- contains granules of copper and is to be used as a thread lubricant but is not approved as a thread sealant. (Generally it is used as a thread lubricant on bolts or pipe threads for mechanical applications where no physical seal is required.)

PTFE tape is only approved as a thread seal when applied correctly. To apply you begin at the end of the pipe and wrap the tape under tension in the direction of the thread turns. Each successive layer should overlap the previous layer by ½ to 2/3 and continue wrapping until the entire threaded portion of the pipe is covered. (Minimum of 3 full turns).

PIPE DOPE:

When looking for pipe dope in the hardware or home supply store we commonly find two types, a tube of dark gray paste labeled "Pipe dope" and tubes or small bottles of white "Teflon Pipe Dope". When selecting the pipe dope check the fine print very carefully to insure the product is listed as approved for the application you intend to use it for as some of these products have a very limited range of applications. As a rule the Teflon pipe dope will have the broadest range of applications and will normally meet all requirements that would typically be found in a residential environment. (My personal reservation with Teflon pipe dope is that it is extremely messy to work with.)

WHICH TO USE?
Providing the Teflon tape or pipe dope is approved for the type of material you intend to convey in the pipe the choice of tape or dope is then a matter of personal preference. Although there is no hard and fast rule that I am aware of, as a rule most plumbers prefer to use pipe dope on all permanent pipe joints, which are pipe joints which would normally be expected to last the life of the structure whereas Teflon tape is often the material of choice when attaching the end use trim out items such as threaded angle stop valves or shower arms and shower heads or in any exposed location where pipe dope might prove unsightly.

As a rule I never make a product endorsement but in the case or pipe dope I will make an exception to that rule.

While there is a number of universal pipe dopes on the market in my opinion the product that is most widely accepted by plumbers, pipe fitters, HVAC techs and electricians, as the standard is a product called "RectorSeal".

RectorSeal is made in both a hardening and non-hardening formula. (The advantage of the non-hardening formula is that the product will not dry out between uses so a small ½ pint container would meet the needs of a homeowner for years to come.)

While other pipe dopes are may be listed for a broad range of applications RectorSeal is listed as approved for but not limited to, Potable water, non-potable water, DWV, Natural Gas, propane, fuel oils (#1 through heavy bunker oils), gasoline, kerosene, diesel fuel, motor oils, lubricants, aviation fuel, jet fuel, high & low pressure air, low pressure steam, high pressure steam, most refrigerants, numerous industrial chemicals, most agricultural fertilizers and electrical conduits in both above grade and direct burial applications.

Although RectorSeal is seldom seen in a hardware or home supply store it can be found in almost all plumbing supply houses, HVAC supply houses and electrical supply houses. In fact, in most trade supply houses if you ask for pipe dope this is the product they will hand you unless you specify another brand.

lazypup,

Thanks for the tutorial. I knew about the white and yellow Teflon only. I use Teflon on water and Permatex formagasket #2 on gas. Permatex is available at most hardware stores.

As I stated above, you must read the product specifications carefully. While Permatex is without a doubt one of the best gasket sealants on the market, nonetheless it is not ASTM certified for use on NPT threads therefore it would not meet code approval for natural gas piping systems.

I second lazypups endorcement. In over 30 years I've yet to come across an instance where RectorSeal could not handle the job and I've yet to find a joint fail because of using it, including the high pressures found in refrigeration and A/C work.

Great replies, thanks! :-)

I happen to have a 2oz. tube of Harvey's Pipe Thread Compound (blue lable). Is this a decent product, or should I look for something like the RectorSeal that LazyPup mentioned?

The sealant will be used to join threaded copper fittings to a brass valve body. All other joints are sweat soldered in a tight space, and reparing a leak would likely require ripping open a tile/CB wall, so it really has to be done right the first time.

Thanks again!

Most useful, I've also wndered about the different type and have certainly seem a variation of quality in the white tape - and now I understand the pink stuff I've seen. I've had a roll of the yellow gas stuff for years, found it where a plumber must have dropped it!

I'll have to read the labels on what teflon paste I find here where I've moved to after living in Australia for years, but I had some teflon paste there that was rated for gas/chemicals etc, which led me to reason it would be ok for automotive cooling systems - I've used it in a couple of places where sensors screwed in etc and it kept the threads from corroding, also I'd noticed a little corrosion on pipe stubs etc where radiator hoses slipped on, so I'd smear a thin film of the stuff on the stub before slipping the hose on. It's worked really well for that.

Careful when using the white teflon for auto sensors..

You may find some sensors and components on an automobile or in electronic circuts that looks like it has the teflon thread seal on it but such is not the case. There is also a white teflon "Heat Sink" compound that looks very similar to thread seal but they cannot be used interchangably. The heat sink material is formulated to convey heat from the component to a finned heat sink or a body component to keep the sensor cooled. The formula used to make thread seal actually has a minor insulation factor and it would be totally counterproductive as a heat sink material.

I third the "Rectum"seal, ha-ha. Use it everyday with high and low pressure gas systems.

Thanks Lazypup, a good point but I do dabble in electronics a bit so know about heat sink compounds, of course you can't use it on oxygen sensors either, nor would it be a good idea if you were looking for an electrical ground. I can't remember what I used it on, but it was pretty much just a plug in a water jacket, and in that instance, it worked fine. Might have to look for some of that Rector seal, and I have to admit I though what Jcal called it too...

My input is: look for compunds that not only meets ATSM and the specification that you are looking for - but is also rated for Stainless Steel fittings as "anti galling".

You will find that there are few. One is made by Loctite corp. It is the most bad a$$ stuff out there, and it's what I use on my own house.

It's $65.00 for a 4oz container.......

{{gwi:2011932}}

I feel pretty strongly about this subject because of my job. When working with natural gas fittings or propane fittings I use yellow teflon tape. After years of experimenting I found a brand that I swear by: Unasco. It is hard to find and a little more expensive but it works great. I can screw and unscrew fittings several times and it stays sealed.

As for pipe dope / pipe paste I found my success using the Loctite listed above. It seems to work very well.

One color the third comment missed:
Silver: contains granules of nickel either powdered or impregnated (I have been told impregnated is better) It can be used as both a thread lubricant and thread sealant. It is designed to prevent galling. I do not have experience with this tape but I know several companies manufacture it including Unasco.

"There is also a white teflon "Heat Sink" compound that looks very similar to thread seal but they cannot be used interchangably."

Not Teflon at all.
It is silicon thermal grease.

A plumber working on my house recommended doing first tape, then going over the tape with dope.

Good idea, or no?

Myself, I've not done much but I do like the teflon tube stuff, although it is messy. I had no idea there was so much to know about pipe dopes and such.

Thanks,

M

unnecessary overkill, done properly either is fine by itself

Thanks Jason.

M

Soooooo, I just got done installing a new LP gas range and had to use a rubber mallet to get it all the way against the wall. Needless to say, it is a VERY tight fit. I used white teflon tape on the two 1/2" gas connections. I did wrap it around about 3 to 4 times and it is very taut. I tested for leaks and there were none. From what I'm reading, I'm taking it that I should somehow shoehorn the stove out and use pipe dope. My question is this...is it a matter of deterioration ? OR Is leak free at the time of install ok ? Thanks everyone, Rock C

Rockoc, If you have a flexible gas connector from the gas shutoff valve to the range it should have flare fittings on each end of the connector. Flare connections are precision machined fittings and you should not have any dope or tape on a flare connection.

rockoc, you're OK with white teflon tape don't worry. I use it all the time for gas fittings when teflon tape is needed(which isn't very often).

Which rector seal should be used for plumbing jobs around the house. I am installing a shower valve.

No 5 is fine.

Forgot to ask too..when installing the male fittings into a shower valve body, and I use the #5 rector seal, and then sweat 1/2 pipe in the fittings just installed...does the heat ruin the rector seal and melt it away?

This applies to low pressure (6 inches WC) natural gas 1 inch black iron.

1. Is there anything wrong with using yellow tape and Reactorseal used together on the same pipe connection?
2.My union has a brass insert which seals with a machined black iron surface. Should any sealant be used with this coupling?
3. Is there any difference between black iron seamless and non-seamless pipe for this application?.
4. Should brass to brass couplings be sealed?
5. Should brass to black iron couplings be sealed?

"Forgot to ask too..when installing the male fittings into a shower valve body, and I use the #5 rector seal, and then sweat 1/2 pipe in the fittings just installed...does the heat ruin the rector seal and melt it away? "

Good question...any advise?

When the teflon came on the market,i started to use the two of them,the teflon first then the compound.i never had leaks in my life after that. I never do this on natural gaz.

What about water fittings? Going from brass to galvanized or copper to galvanized? I have used white teflon and tru-blue with some success. I am thinking the Red would be better since its up to 1.5- 2.5" connections seeing temps of 190degrees and pressure up to 150psi.

"Going from brass to galvanized or copper to galvanized?"

A dielectric fitting is required to change from ne material to another.

Teflon tape works fine on the NPT threads.

That is correct the galvanized connection I am using is a dielectric.

I have one year old a GE profile Double Oven range converted to propane. Lately smell gas and I detected a small leak on the input flex hose to the end of range (bottom valve);
[flexible gas connector from the gas shutoff valve to the range]
What shall I use? I perfectly understand that I can use rather than yellow tape Gas dope as "RectorSeal", LocTite's anaerobic or Permatex formagasket #2. Which one is greatly available and where can I buy from? I don't want to spend $65 for a problem I detected myself without any technician from Sears or so.
I am living in Hamden , Connecticut.

PTFE (Teflon) Tape and pipe dope is only intended to be used on NPT (National Pipe Taper) threads. these products should never be applied to Flare or compression connections.

Found out that dryer gas lines are flared-don't need tape. After a month, decided to see if it was leaking-poured soap mixed with water over, then took it apart.

hooking up lines to regulater on propane, do i need pipe dope on brass to brass fittings

Does anyone know if the Teflon Pipe Thread Sealant will corrode rubber gaskets over time? I am rebuilding a toilet and multiple DIY sites recommended coating all of the rubber gaskets, including the tank to bowl gasket, with Teflon Pipe Thread Sealant for added protection. The toilet is above the parlor and can not afford to have a leak! Will the Teflon Sealant shorten the life of the gaskets? The sealant can does not mention anything about rubber! Thanks in advance! Tom.

"...and multiple DIY sites recommended coating all of the rubber gaskets, including the tank to bowl gasket, with Teflon Pipe Thread Sealant for added protection..."

This is a problem with DIY and interwebz both.
I suggest a daily litre of single malt, your choice, in eliminating bothersome issues.

Don't believe everything you see and hear.

Hey Alphonse..thanks for the advice! The litre of malt a day will force me to take many daily leaks.....and I need to fix my potty before I do that!

I do not believe everything I see, hear or read on the internet. That is why I came here to ask...because I was impressed by responses such as the one given by lazypup on this forum. Looks like they are busy at this time.

Tom

I saw the following queston asked above... but nobody really answered it and I am doing a project where I need to ask the same question.. That is:

When installing the male fittings into a shower valve body, and I use the #5 rector seal, and then sweat 1/2 pipe in the fittings just installed...does the heat ruin the rector seal and melt it away?

Sweat stubs or as much pre-fab as you can to the male fittings before installing. Then wrap the assembly with a wet rag and continue.
That doesn't directly answer your question. I never sweat or braze on any threaded assembly unless specifically intended as such,i.e. NPT X C or where I know heat won't destroy possible plastic components.