Answer: Generally yes, but threads should never be assumed to be identical.

In the United States, pipe thread (aka National Standard Pipe Taper NPT) is used in sizes 1/8-2 inches and ISO metric thread (which is called British Standard Pipe [BSP]) is used in sizes above 2 inches. The difference between the two pipe systems is how a threaded joint associates with a smooth surface – a “tangent line.” In BSP, the tangent line for fittings going into an enclosed space slants sideways after 180 degrees have been turned through its center. This means that there needs to be an allowance made to allow free movement for this type of joint if it’s opposed by high pressure from below.