Pipe dope versus Teflon tape
Because pipe threads are tapered, it is necessary to apply pipe thread sealant (pipe dope) or pipe thread tape (such as Teflon tape) to fill in the gaps and prevent leaks. Although both products create a strong seal around the joint in water, gas, and air systems, choosing between the two goes beyond personal preference. For example, pipe dope is often the better choice when working with gas lines and stainless-steel connections, which often have coarser threads. However, it is not suitable for soft plastic pipes. In comparison, Teflon tape is generally safe for all pipes 1” or less, and it lasts indefinitely. In this article, we compare pipe dope and Teflon tape, as well as review when and how to use each.
Pipe dope and Teflon tape comparison chart
| Pipe Dope | PTFE Tape | |
|---|---|---|
| Sealant Type | Thick paste | Non-adhesive tape |
| Cost | Costs more than PTFE | Generally, less expensive |
| Installation | Cover threads with paste, May be messy | Slight learning curve, Too much thread tape can prevent full tightening |
| Re-Application | Apply directly on top of the old paste | Must remove all existing tape before re-application |
| Thread Size | Coarser NPT** threads | 1” or less |
| Pipe Material | Metal pipes, Stainless steel, Brass | Safe on most pipes, including plastic, Compression fittings |
| Pressure Systems | High-pressure | Low-pressure |
*These are general guidelines. Please review the product information before application and comply with local codes.
**National Pipe Tapered, ANSI/AMSE B1.20.1
What is pipe dope?
Pipe dope is a joint compound that creates a leak-proof and pressure-tight seal around pipe threads. In addition to making a reliable seal, it also lubricates the joint, so it is easier for the parts to slide together during assembly and apart when disassembling. Other names for pipe dope include:
- Thread sealant paste
- Pipe thread sealant
- Teflon paste
How is pipe dope applied?
Pipe dope is a thick paste. Most often, it is packaged in a small container with a brush attached to the underside of the lid. Simply use this brush to smear the joint compound all around the pipe threads. Then, assemble the connection as usual.
When to use pipe dope?
Pipe dope is preferred for propane and natural gas applications where the pipe threads are wider. This is because the compound’s thick consistency fills coarse thread gaps more effectively than PTFE tape. Furthermore, correctly applied thread sealant paste provides extra strength for high-pressure systems. Not all pipe dope is equal - check manufacturer ratings before applying the sealant. Pipe dope is not recommended for all pipe materials, and it may degrade plastic joints. It is safe on stainless steel and other metal pipes.
What is Teflon tape?
Teflon tape is both a sealant and a lubricant for threaded connections in water, gas, and air systems. The thin, non-adhesive tape fills the thread voids to ensure a leak-free joint. Teflon tape is a name brand–professional contractors also refer to it as:
- Plumber’s tape
- Pipe thread seal tape
How is Teflon tape applied?
Wrap the thread seal tape tightly around the pipe threads clockwise when facing the pipe’s end. This ensures the tape does not unravel when tightening the joint. Leave the thread nearest to the pipe opening bare so the tape does not interfere with the pipe’s flow. If re-applying plumber's tape, first remove the old tape. Overwrapping may hinder full tightening.
When to use Teflon tape?
PTFE tape is suitable for water, gas, and air systems. It is safe for most pipe materials, including plastic pipes. Various thicknesses are available to meet application requirements. As a general rule, use Teflon tape when the thread size is an inch or less.
What color PTFE tape do I need?
While it is not a hard-and-fast rule, plumber's tape is often color-coded according to its thickness or application. Always check the manufacturer's guidelines before use.
- White PTFE tape - The most commonly used plumber’s tape, it is suitable for water-tight seals.
- Pink (or red) PTFE tape - The plumbers’ and pipe fitters’ go-to for pipes up to about 2 inches, it is heavier than the standard white seal tape.
- Yellow and blue PTFE tape - The go-to Teflon tape for gas line joints.
- Gray PTFE tape - Use for stainless steel applications to prevent corrosion and seizing.
- Green PTFE tape - Use for air/oxygen lines.
When to use pipe thread sealant versus PTFE tape?
| Thread Sealant / Pipe Dope | PTFE Tape / Teflon Tape | |
|---|---|---|
| General Applications* | High-pressure, Gas | Low-pressure, Water, Air, Gas |
| Fitting Size | Larger threads | Threads 1” and smaller |
| Pipe Material* | Stainless steel, Brass, Galvanized | Suitable for all pipe materials |
*Check product ratings and local regulations to confirm code compliance.
FAQS: Threaded Pipe Connections
Can I use PTFE tape and pipe dope together?
Yes. Use Teflon tape and pipe dope together for critical, high-pressure systems. Wrap the male threads with PTFE tape first. Then apply a light coat of pipe joint compound.
Should I use pipe dope or Teflon tape for gas lines?
For most gas line systems, it’s recommended to seal joints with pipe dope, rather than Teflon tape. This is because the pipe dope’s thick paste fills the large thread gaps better, ensuring a leak-free connection.
Is pipe dope safe for plastic connections?
Some joint compounds are compatible with plastic pipes; however, this is not always the case. Pipe dope may interact with the plastic, corroding the joint. When possible, use Teflon tape for plastic connections.
What is NPT?
NPT stands for National Pipe Tapered, as referred to in ANSI/AMSE B1.20.1. It outlines dimensions, tolerances, and other specifications related to threaded pipe.
What does PTFE stand for?
PTFE is an abbreviation for Polytetrafluoroethylene, often referred to as Teflon. It is highly corrosion-resistant and withstands high temperatures.
Can I put Teflon tape over old thread sealant?
Before applying the new PTFE tape, first remove any existing tape.
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