Wait until the threadings are completely dry before you apply Teflon tape. If the threadings are wet, then your tape won’t seal them properly.
If stray bits of tape cover the first threading or extend past the end of the pipe, they may block the flow of water or gas, which could lead to clogs or weak pressure.
The number of times you wrap your pipe depends on its thickness. Use 1–2 wraps for 1⁄4–3⁄8 in (0. 64–0. 95 cm) pipes, 2–3 wraps for 1⁄2–3⁄4 in (1. 3–1. 9 cm) pipes, or 3–4 wraps for 1–1 1⁄4 in (2. 5–3. 2 cm) pipes. Most pipe threads run clockwise, but always double check the one you’re wrapping to ensure you tape it properly. If you apply thread seal tape in the wrong direction, it could fray or bunch up when you try screwing it in, which will ruin the seal.
If the tape bubbles away from the threads or has any edges that are bunched-up or loose, then take it off and reapply it.
Pipe dope, also known as pipe joint compound, is a liquid sealant that fills in the gaps between threads when you screw it in. Even if you aren’t working on pressurized pipes, many plumbers add a layer of pipe dope over Teflon tape anyway for extra protection from leaks. If you’re sealing PVC pipes, check that the pipe dope is compatible with plastic first. If you use one that’s incompatible, it could damage the seal.
If you can’t see the shape of the threading through the tape, then you applied it too loose. Take off the tape and pull it tighter as you reapply it.
Avoid using white general-use tape on gas lines since it’s not thick enough and could cause leaks.
After you attach the pipe, check it for leaks. If you still notice leaks, then you may need to reapply the tape or add pipe dope to the connection.
