Short definition
PTFE tape (Teflon tape) is a thin polytetrafluoroethylene tape wrapped around the male threads of a pipe connection to seal and lubricate the joint. White is for water, yellow for gas, pink for heavy-duty water. Wrap clockwise (as viewed from the threaded male end) so the tape tightens, not unwinds, as the nut goes on.
What it is
PTFE tape doesn’t actually “seal” the threads in a chemical sense — it lubricates and fills the helical clearance between male and female threads. The seal comes from thread engagement under wrench torque. Standard residential thicknesses:
- 2 mil — white water tape
- 4 mil — yellow gas tape, pink heavy-duty water tape
- 6 mil and up — high-pressure / industrial
For potable water, the tape must be ANSI/NSF 61 listed (or paired with an NSF-listed pipe joint compound).
WA practice typically uses 4 to 6 wraps on water threads, 3 to 4 on gas. Always wrap in the direction that tightens the tape under thread engagement — clockwise from the male-end view.
Why it matters to a homeowner
Two errors cause most PTFE leaks:
- Wrapped backward. Tape unwinds as the fitting screws down, leaving the threads bare. Always clockwise from male end.
- Wrong color on gas. White (water) tape on a gas joint is a code violation in WA. Yellow gas tape exists for exactly this reason — see gas-rated Teflon tape.
A practical rule: tape goes on threads only, never on a flare seat, ferrule, or compression fitting. The seal on those joints comes from shape, not from tape. Tape on a flare face routinely causes leaks at icemaker hookups and gas-range flex lines.
Common variants and not the same as
- White vs. yellow vs. pink. All PTFE; different densities and certifications. Yellow is the only color rated for fuel-gas service.
- PTFE tape vs. pipe joint compound. Tape is cleaner; dope is more forgiving on imperfect threads. Either works for water; for gas, see local code (most accept either, many WA gas fitters use both yellow tape and gas-rated dope).
- PTFE tape vs. UK hemp/linseed paste. UK practice uses hemp and boss-white; US standard is PTFE.
Common failure modes
- Wrapped backward. Tape unwinds; threads bind unsealed.
- Too few wraps. One wrap is insufficient. Four to six is standard for water.
- Too many wraps. Ten or more extrudes outside the joint and can clog flow restrictors downstream.
- Tape on flare or ferrule. Tape goes on threads only.
- White tape on gas. Code violation in WA — use yellow.