While a single plumbing project might require both plumber putty and Teflon tape, you cannot substitute one for another. Teflon tape provides a reliable seal in the joints of threaded pipe for liquids and gases that may be under considerable pressure. The plumber’s putty acts as a flexible sealant in situations where resistance is needed water, but cannot withstand any significant pressure.
Teflon tape
Teflon tape, also known as PTFE (polytetrafluoroethylene), is a thin film that functions as a sealant in threaded pipe joints. Different types and densities of PTFE tape are coded by colored for various uses. The white ribbon found in any hardware store or shop DIY is suitable for water supply pipes up to 3/8 inch (0.95 cm) in diameter. The yellow tape, which is twice as dense as white, is for use on gas lines. The red ribbon is for use on larger pipes 1/2 to 2 inches (1.3 to 5cm). There is also green ribbon for oxygen and medical gas lines, and copper, which acts as a lubricant rather than as a sealant.
Use Teflon tape
Start at the end of the pipe with the male thread and wrap the ribbon around the thread in a clockwise direction, overlapping the previous half-turn until it reaches the end of the thread. The thin film will easily adapt to the contours of the threads. Screw the other side of the joint down to get a full seal and pressure resistant.
Plumber putty
The different brands of plumber putty have different ingredients. But all of them are repellent to the water, and all remain soft and flexible for a long time. This makes them ideal for applications where a waterproof reversible seal is required, but only when the seal will not be under pressure (because if the putty remains soft it will wash or leak). Typical domestic plumbing applications for putty are as a sealant between the base of a faucet and the surface of a sink, and between the trailing edge of a basket and a sink.
Use Plumbing Putty
In the event of a leak, put a generous layer of mastic around the bottom edge of the leak and then place it in the drain hole in the sink. Squeeze the drain underneath according to the instructions, and then wipe off excess putty with a damp cloth. For a faucet, use a thick cord of caulk around the faucet base prior to positioning it in the sink. Squeeze the faucet and wipe off excess caulk.
Alternatives
You should never have to choose between Teflon tape and plumber putty, because they do not do the same job. However, there are alternatives for each. Some plumbers prefer to use a liquid compound for pipes (also called “pipe lacquer”) instead of tape. And in some cases, such as in granite, where plumber’s putty is undesirable because it can cause stains, and silicone putty is a better choice.