What's the Difference: Joint Sealing with Teflon Tape and Pipe Dope - Fine Homebuilding
previous
  • Deck Design & Construction
    Deck Design & Construction
  • Master Carpenter Videos
    Master Carpenter Videos
  • Video: Install a Fence
    Video: Install a Fence
  • Clever daily tip in your inbox
    Clever daily tip in your inbox
  • 7 Trim Carpentry Secrets
    7 Trim Carpentry Secrets
  • 9 Concrete Countertops Ideas
    9 Concrete Countertops Ideas
  • All about Roofing
    All about Roofing
  • 12 Remodeling Secrets
    12 Remodeling Secrets
  • Remodeling in Action
    Remodeling in Action
  • Read FHB on Your iPad
    Read FHB on Your iPad
  • Video: Build a curved step
    Video: Build a curved step
  • Magazine Departments
    Magazine Departments
  • Video Series: Install a Rock-Solid Tile Floor
    Video Series: Install a Rock-Solid Tile Floor
  • Basement Remodeling Tips
    Basement Remodeling Tips
  • Energy-Smart Details
    Energy-Smart Details
  • 7 Smart Kitchen Solutions
    7 Smart Kitchen Solutions
  • Gallery: Custom Flooring
    Gallery: Custom Flooring
  • Solid Deck-Framing Advice
    Solid Deck-Framing Advice
  • 7 Small Bathroom Layouts
    7 Small Bathroom Layouts
  • Tips & Techniques for Painting
    Tips & Techniques for Painting
next

Fine Homebuilding: The Magazine

Fine Homebuilding: The Magazine


What's the Difference: Joint Sealing with Teflon Tape and Pipe Dope

comments (4) March 5th, 2009 in Blogs
RDA Robyn Doyon-Aitken, producer

Dope stays gooey. Pipe dope never hardens, so it will never become brittle and flake out of a joint.
Tape is less messy, but theres 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.
Dope stays gooey. Pipe dope never hardens, so it will never become brittle and flake out of a joint.Click To Enlarge

Dope stays gooey. Pipe dope never hardens, so it will never become brittle and flake out of a joint.

Photo: Krysta S. Doerfler

by Rob Yagid

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

pipe dope
Dope stays gooey. Pipe dope never hardens, so it will never become brittle and flake out of a joint.

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

Teflon tape Simmering brine
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.

posted in: Blogs, water and moisture control, plumbing

Comments (4)

Advancedemc Advancedemc writes: Hm nice question

Teflon tape comes in a variety of qualities. Some good and some bad. I foolishly used teflon tape when plumbing all the iron gas piping in my home and I could not get the system to pass the leakdown test I conducted. I ended up taking it totally apart and used Master's compound. Problem solved.

When I built a water truck for my son, I used teflon tape again, thinking that the water pressure in the tank was minimal. Once again I ended up dismantling the iron fittings and using Master's compound to eliminate the leaks. Where I have found teflon tape to work fairly well is when doing brass to brass air line fittings. Other than that, I will stick with the Master's because I have had more failures with teflon tape than with the Master's.
Posted: 5:12 am on May 14th

BGodfrey BGodfrey writes: I have used teflon tape for probably 35 years or more, but almost always on plastic, copper, brass, or bronze joints. And rarely with a leak. Today I spent hours assembling a complex manifold for a sprinkler system using galvanized steel pipe and fittings and bronze valves and hose bibs. I used Teflon tape, three layers, applied in the correct direction, and tightened the fittings very tight, but not so tight as to crack them. Fortunately I had the sense to pressure test it before I set it in concrete. It leaked all over the place.

Now I am going to have to take it all apart and redo it. If I use dope will I be happy, or will I just feel like a dope?
Posted: 6:35 pm on March 8th

mathman1 mathman1 writes: In my experience as a handyman, teflon tape seals better than pipe dope because teflon tape is solid and is strong upon its compression during the pipe assembly and stays in place whereas pipe dope is a viscous but fluidic filler which just get pushed out by the 40 psi water or 1/4 psi gas pressure. Due to a defect in the thread, a leak channel can form most often along or possibly over the mating threads upon assembly which is supposed to be filled by the pipe dope or teflon tape. I have seen pipe dope get pushed out by the water or gas pressure and result in a leak whereas teflon tape holds in place and does not leak. Brass pipes are especially problemic due to its softness even if the threads look perfect they are best sealed with teflon tape. Brass fittings on gasoline engines are best sealed with teflon tape if there is a leak. Teflon tape last forever in your tool chest since it does not dry up. I have encountered various situations with leaks using pipe dope and teflon tape has solved the problem. Its to the point where writing this, I have given up on pipe dope.
Posted: 5:14 pm on April 11th

thmecharlie thmecharlie writes: Couple thoughts on this: teflon tape is sold/marketed as a pipe joint sealant. What is teflon? a lubricant! it allows pipe joints to be tightened to a leak resistant point because it lubricates the operation, as stated it may also fill void in the thread to prevent leakage. Look at a disassembled teflon joint. where is the tape? Mostly not there.
Pipe dope on the other hand also lubricates assembly (most contain teflon)and fills voids. lok at a disassembed joint you can see the reguired amount of dope in the joint it did not roll/squeeze/disintegrate.
Pipe threads are designed and manufactured with a taper. this makes them tighter the more they are screwed together, and is also what makes them not leak. any lubricant will allow them to be tightened sufficiently.
Pipe dope stays in and around joint area helping to prevent corrosion, and stays in the area. teflon has no anti corrosion properties.
I always use Pipe Dope, it works better for me and find i do not have to tighten joints to the extent that i had to with teflon tape. i occasionally had tightened teflon joints to the point of distortion and was unable to make them stop leaking. never had that problem with Pipe Dope.


Posted: 3:32 pm on March 23rd

Log in or create a free account to post a comment.