Making NPT Connections

American National Standard Pipe Thread standards, often called national pipe thread standards (NPT) for short, you may also see the following short forms for female threaded fittings FNPT, FPT & FIP, for male threads MNPT, MPT and MIP are used.

Metal Fittings

A general guideline for making a NPT threaded connection for metal fitting is as follows.

After hand-tight engagement, tighten an additional:

1-½ to 3 full turns for sizes up to 1”

1 to 2-½" full turns for sizes 1-¼" and larger

You should have between 3-1/2 and 6 threads engaged. Thread engagement outside of this range may indicate either under or over tightening of the joint or out of tolerance threads. With experience you will know when the tightening force feels “right”, and you will know when to stop tightening before you damage the fitting or valve.


Visit the following link for installation requirements for making Stainless Steel NPT connections, Due to the extreme hardness of stainless alloys, and the issues regarding galling, the sealing of S.S. threaded connections can be much more challenging than when working with brass and or bronze alloy fittings.

Sch. 40 & 80 PVC / Plastic Fittings