IPS (also known as NPSH) is the left circled column, NPT is the right. You can see that the actual outside diameters are very close, and threads-per-inch (TPI) are the same. Does this similarity mean you can get a liquid-tight seal screwing IPS and NPT fittings together? No, absolutely not.

Is NPT same as IPS?

National Pipe Tapered (NPT) and Iron Pipe Straight (IPS) are two commonly used thread standards in plumbing. ... To the left are a set of circles corresponding to pipe sizes commonly used in domestic plumbing, labelled with their nominal NPT or IPS sizes. NPT and IPS nominal sizes are always the same.

Are NPT and IPT threads compatible?

IPT (Iron Pipe Thread) is equivalent to NPT; Some sources also refer to IPS (Iron Pipe Straight); using IPS risk confusion with NPS listed below.