Sealing N.P.T. threads can be an exasperating experience if certain techniques are not followed. The following tips will help alleviate many common problems in thread sealing:

     1. Always use some type of sealant (tape, paste, or liquid thread sealant) and apply sealant to male thread only, if using a hydraulic sealant, allow sufficient curing time before system is pressurized. Leave the first 1 to 1-1/2 thread exposed.
     2. When using tape sealant, wrap the threads in a clockwise motion starting at the first thread and, as layers are applied, work towards the imperfect (vanishing) thread. If the system that the connection being made to cannot tolerate foreign matter (i.e. air systems), leave the first thread exposed and apply the tape sealant as outlined above.
     3. When using paste sealant, apply to threads with a brush, using the brush to work the sealant into the threads. Apply enough sealant to fill in all the threads all the way around.
     4. When connection one stainless steel part to another stainless steel part that will require future disassembly, use a thread sealant that is designed for stainless steel. This stainless steel thread sealant is also useful when connecting aluminum that needs to be disconnected in the future.  These two materials gall easily, and if the correct sealant is not used, it can be next to impossible to get them apart.
     5. When connecting parts made of dissimilar metal (i.e. steel and aluminum), standard tape or paste sealant performs satisfactorily.
     6. For sizes 2” and below, tape, pate or liquid thread sealant performs satisfactorily. When using thread tape, four wraps (covering all necessary threads are usually sufficient).
     7. For sizes 2-1/2” and above, thread paste is recommended. If thread tape is used, eight wraps (covering all necessary threads) is usually sufficient. Apply more wraps if necessary.
     8. For stubborn to seal threads, apply a normal coating of thread paste followed by a normal layer of thread tape.
     9. For extremely stubborn to seal threads, apply a normal coating of thread paste followed by a single layer of gauze bandage followed by a normal layer of thread tape.


When this procedure is done, the connections become permanent. Extreme measures will be necessary to disconnect these components. All other measures to seal the threads should be explored prior to use of this technique.

     10. Over-tightening thread can be just as detrimental as insufficient tightening. For sizes 2” and below, hand tighten the components and, with a wrench, tighten no more than 1 to 1-1/2 full turns.