What’s the Difference: Joint Sealing with Teflon Tape and Pipe Dope
The success of any plumbing project hinges largely on the quality of its joints. Threaded connections between metal or plastic parts can be particularly problematic if not sealed properly. Teflon tape and pipe dope are used to fill voids between male and female threads to make joints leakproof and to prevent metal parts from rusting together. People often use pipe dope on top of Teflon tape, but some manufacturers say there is no benefit to that usage and that Teflon tape and pipe dope perform the same whether they’re used individually or together.
Pipe dope is easier to apply
Pipe dope, technically known as pipe-joint compound, is available in containers as small as 1 fl. oz. and as large as 32 fl. oz. To apply pipe dope to the male end of a threaded pipe or fitting, swab the threads with the supplied brush full of compound. Although using pipe dope can be a bit messier than sealing with Teflon tape, it’s faster. Similar to Teflon tape, pipe dope comes in versions designed for water lines and for gas lines. Read packages carefully because all dope cannot be used on plastics.
Approximate cost: $3 per 8-oz. can
Teflon tape is less messy
Teflon tape, which is available in 1⁄2-in. to 1-in. widths, comes in high- and low-density versions. While Teflon tape is less messy than pipe dope, it can be more difficult to apply properly. If wrapped wrong (in a counterclockwise direction), the tape can ball up as components are tightened, ruining the seal. Many pros complain about the quality of low-density tape, which is less expensive. More low-density tape is required to seal a joint properly because it compresses more than high-density tape. Low-density tape also tends to shred easily. A strand of tape that finds its way into a plumbing line can cause problems.
Approximate cost: $1 per roll
More on Plumbing:
How To Connect PVC Pipe – Learn how to prepare plastic pipe fittings, apply primer and cement, and make the connection between the two parts.
How to Make Basic PEX Connections – PEX components are user-friendly, leave water systems immediately ready for inspection, and don’t require glue joints to set up. Learn how PEX connections can make your next plumbling job easier.
The Right Way to Join Plastic Pipe – Both PVC and ABS plastic pipe are so easy to work with that they’re often slapped together without much thought. Are you sure you’re joining them correctly?
Dope stays gooey. Pipe dope never hardens, so it will never become brittle and flake out of a joint.
Tape is less messy, but there's a caveat: If wrapped wrong (in a counterclockwise direction), the tape can ball up as components are tightened, ruining the seal.
Teflon tape for residential plumbing is color-coded. High-density pink tape is used on water lines; yellow tape is designed for gas-line use. White tape (often low density) is used on water lines.