by Stuart Spaulding —
CLIA Certified Landscape Irrigation Auditor Training & Communications Manager at DIG Corp.

Teflon Tape:  Where (& where not) to Use

 Before talking about Teflon tape or any thread sealant products used in the domestic irrigation industry, it’s a good idea to be aware of the difference between fittings with “hose” type threads, and those with “pipe” type threads.

“Hose” Threads

“Hose” threads are the type of threads that are found on a typical garden hose, hose-end timer, Y splitter, hose-end sprinkler, and residential outdoor faucet.  They can be ¾” male (MHT) or ¾” female (FHT).  These threads are farther apart from each other than pipe threads, and they screw together and seal against a washer which must be in place in the female fitting to be leak free.  No Teflon tape or thread sealant should be applied to hose thread connections.  Normally they are tightened (clockwise) by hand; wrenches or pliers are typically not necessary to achieve the tightness needed for a leak free connection.

“Pipe” Threads

“Pipe” threads are the type of threads found on PVC fittings, irrigation valves and sprinkler heads and risers.  They are available in a variety of outside diameters, and the threads are tapered & closer to each other than “hose threads”.  These fittings do not seal by using a washer; instead pipe thread connections are sealed between the male and female threads by applying Teflon tape (to the male threads) and tightening the two fittings with pliers or a wrench.  Never try to join ¾” female pipe threads with male hose threads or vice versa, they may appear to fit but they will leak, and the threads may be damaged in the process.

Teflon Tape

Pipe thread fittings will leak if no thread sealant products are used.  There are a variety of products that can be applied to pipe thread fittings to prevent them from leaking.   Pipe dope and thread sealant pastes are common in the plumbing industry and are often used on brass and copper fittings. But they can cause damage to some plastics over time. Do not use pipe dope on plastic irrigation products.  Always use Teflon tape on pipe threaded plastic irrigation products and PVC fittings and nipples.

Teflon tape alone does an excellent job of sealing plastic pipe thread connections, and it will hold up for many years if it is applied properly.  Follow these steps to ensure a leak free, long lasting connection:

  1. Make sure the male and female threads are un-damaged, clean, and free of any grit, particles or old pipe sealant or tape. If necessary, clean the threads by brushing them with a soft brush under running water.
  2. Start at the end of the threads & wrap the Teflon tape tightly around the male threads in a clockwise direction until all the threads are covered by about 4 to six layers of Teflon tape.
  3. Turn the male threaded fitting clockwise into the female threads and continue turning until it is as tight as possible by hand.
  4. A final tightening needs to be done to produce a leak free connection. This is done by using pliers or wrenches to grab & turn the fitting an additional revolution or two clockwise until the fittings are snug and “wrench” tight.  Do not overtighten.
  5. The last step is to open the water supply valve, pressurize the line and inspect the connection for leaks. If any leaks are visible, shut off the water supply and re-tighten the fittings.