NPT - Female thread


NPT female thread

American NPT pipe thread ANSI / ASME B1.20.1 - 1983

D Lmin Code A3 A7 A11 E5 S15
1/8-27 NPT 10 NI 18 OK OK OK OK OK OK
1/4-18 NPT 11 NI 14 OK OK OK OK OK OK
3/8-18 NPT 12 NI 38   OK OK OK OK  
1/2-14 NPT 15 NI 12   OK OK OK OK  
3/4-14 NPT 17 NI 34     OK   OK  
1-11.5 NPT 19 NI 01     OK      

The NPT thread has a tapered form. To ensure a leak-tight seal, the use of a pipe thread sealant is recommended. One commonly utilized technique is Teflon Tape, wich you wrap twice clockwise around the male end. Note that the pipe thread sealant may have lower temperature capabilities than the valve (e.g. Teflon Tape max 450°F).