Posted on January 28, 2022

Should You Use Teflon Tape on Brass Fittings?

John Joyce
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John Joyce

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Teflon™ tape, also known as PTFE tape (polytetrafluoroethylene), is widely used on pipe threads in a variety of applications, from commercial and home plumbing to industrial use. PTFE is a hydrophobic that repels water, meaning water or liquids containing water cannot make PTFE tape wet. In addition, Teflon (PTFE) is less likely to cause friction against other solids.

Teflon tape, often referred to as plumber’s tape, is a type of thread sealant and lubricant used to prevent leaks and keep threads from seizing. It was originally used by the military to help machinery run more smoothly by reducing friction between moving parts. It was then realized that its water sealing properties provide an ideal sealant on threads, including sealing joints on fuel lines, plumbing fittings and even fasteners to lubricate the threads.

Using Teflon Tape on Brass Fittings

When threading male threads into mating female threads the use of Teflon tape on brass fittings is highly recommended as long as the fitting does not already have an O-ring or rubber gasket. Teflon tape is extremely flexible and easily presses into the threads as the fitting is being seated into its female counterpart, providing a leak tight connection. It is ideal for threaded brass connections of any type, such as threads on brass fittings, valves, brass hose fittings (used on the thread end, not the barbed end) and also the threads on steel pipe and fittings.

It’s imperative to apply Teflon tape in the same direction of the thread, which is clockwise on most fittings. If the tape is wrapped in a counterclockwise direction (or against the direction of the thread) it will unravel when mating into the female connection. Also, do not use too much Teflon tape as this could be counterproductive and prevent the joint from sealing properly and/or causing the tape to gum up.

Using Teflon Tape on Brass Compression Fittings

DO NOT use Teflon tape under the compression nut or on flare threads of brass compression fittings (or a compression fitting of any other material)! Liquid or gas does not touch those threads. When tightening the nut on a compression fitting of any material (brass, stainless steel, or other material) the ferrule provides the seal by squeezing the tubing. Tape would most likely cause the compression fitting from tightening properly. However, when a brass fitting is compression to male thread (i.e., NPT male), where the compression end mates with a tube and the male NPT mates with a female connection, then Teflon tape is the best choice for ensuring a tight seal of the NPT joint.

Using Teflon Tape and Thread Sealant Paste

Many people recommend using a combination of Teflon tape and a silicone-based joint compound on threaded brass fittings to ensure the joint is completely leak free. As referenced above, the most common is an NPT thread, which is a tapered male and female thread that is best sealed with Teflon tape and/or jointing compound. When using both, it’s suggested to wrap the tape first, then apply the joint compound around the thread and wipe any excess with your finger. The combination of PTFE tape and joint compound provides extra protection to makes sure the joints on brass fittings will not leak. Though it’s not always necessary to take the extra step of applying joint compound, many people strongly recommend it on any new heating installation that can potentially experience expansion and contraction of the joint.

Different Colors of PTFE Tape for Different Applications

Standard white PTFE tape is primarily used in either potable or non-potable water system connections because it is corrosion and acid resistant. Standard PTFE tape works best in high pressure lines and is resistant to many chemicals.

Specialty PTFE Tapes

Specialty PTFE tapes come color coded for specific applications to help ensure the correct tape is being used for the application. Specialty PTFE tapes have a considerably higher density and are much thicker than standard tape.

For instance, White Premium High Density tape is obviously white in color too and is good for all industrial applications. There are no additives or pigments which makes it ideals for applications including water, oil, and food processing and other applications where non-contamination standards are required.

Other Color Coded PTFE Tapes

The other color coded tapes are self-describable and include:

  • Pink Plumbers Tape used by plumbers and pipe fitters
  • Yellow Gas Line Tape for gas lines of all types; propane, butane lines and natural gas
  • Green Oxygen Tape is grease free and does not support combustion
  • Gray Stainless Steel PTFE Tape has a nickel pigment color added to ensure its use with all stainless steel fittings

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