Tapered threads are the most common type of thread available. As the name implies, they have a slight taper. When mated together and tightened, the threads compress and may form a seal.
Usually a thread sealant is required. The mating threads both hold the fitting in place and seal the connection.
The most widely used pipe threads in North America are NPT (National Pipe Taper). Some confusion may result from the use of NPT, FPT, and MPT in describing threads.
Both FPT and MPT are NPT threads, with FPT meaning female threads (internal) and MPT meaning male threads (external).
NPTF (Dryseal) threads are modified NPT threads, which are less likely to leak without a sealant. For a leak-free seal, we recommend using a sealant compound or PTFE tape. You can use NPTF threads with NPT threads, but you’ll lose some of the leak-free characteristics