Thread Seal Tape Joints

Sizing Thread Seal Tape (PTFE / Teflon) for Joints

Thread seal tape, the stuff most people just call Teflon tape, is unsintered PTFE (polytetrafluoroethylene). It seals because it deforms inside the thread grooves and fills the clearances. To estimate how much you'll burn through per joint, use Ltape = njoints × v × π × d. Here v is 5 to 7 turns wound clockwise on the male thread as you look at the tip, d is in metres, and density sits somewhere between 0.95 and 1.45 g/cm³.

On water and compressed-air lines the standard white tape (0.075 mm) does the job. Natural gas is a different story: ABNT NBR 7198 wants the thicker yellow tape (around 0.1 mm), denser and certified for fuel gases. And if you're dealing with loose threads, oversized bores or worn fittings, tape alone won't cut it. Reach for an anaerobic liquid pipe sealant or a sealing paste.

Applications

Sealing threaded connections in household plumbing (taps, showers, water heaters), water and air filters, pressure gauges, brass fittings, PPR/PVC adapters with metal inserts. On LPG and natural gas work, always reach for the yellow tape and never the white, and follow the protective-sleeve and pressure-testing rules in NBR 7198 / NBR 13523.

FAQ

Which way do I wind the tape? Clockwise on the male thread, looking straight at the end of the pipe. Wound that way it tightens as you screw the fitting on rather than peeling off.

5 turns or 7 turns? Five turns is plenty for fine threads (1/2″ and 3/4″). Bump it up to 6 or 7 for larger diameters (1″ and up) or when the thread is a little worn.

Is sealing paste better than tape? On large or worn threads it is, since the paste fills the bigger gaps. On new standard threads, white PTFE tape works fine and it's a lot less messy to put on.