Brass Fitting Thread Types Explained: BSP, NPT, BSPT, JIC

Walk into a plumbing merchant in London, a hydraulics shop in Houston, and an engineering supplier in Munich and ask for a "½-inch brass fitting." You will get three physically different products that look similar, share the same nominal size designation, and are completely incompatible with each other. This is the thread standards problem, and it has been causing expensive mistakes since globalisation made multi-market procurement the norm.

I deal with this every week. Let me explain each standard clearly and completely, so you can specify correctly the first time.

BSP — British Standard Pipe

The foundation of pipe thread standards across the British Commonwealth, Europe, Asia, and much of the world. All BSP threads share the same thread form: a 55° included angle with rounded crests and roots (Whitworth form). What differs is whether the thread is parallel or tapered.

BSPP — British Standard Pipe Parallel (also called G thread)

The most common BSP variant in Europe. Threads are parallel — constant diameter along the thread length. Size designation: G ½, G ¾, G 1, etc. (the G prefix is the ISO designation; BSPP in British nomenclature).

Sealing: Parallel threads do not seal on the thread itself. Sealing requires either: a bonded washer/O-ring on the face (most common), or a thread sealant compound filling the thread gap. PTFE tape alone on a parallel thread will not give a reliable seal — the tape just moves under pressure.

Where used: Germany, France, Netherlands, Scandinavia, and as the metric/industrial standard across the EU. Also widely used in hydraulic connections, instrumentation, and pneumatics globally.

BSPT — British Standard Pipe Taper (also called R thread)

Same 55° thread form, but with a 1:16 taper (3.58° half-angle). The taper creates an interference fit as you tighten — the thread seals itself with the assistance of PTFE tape or thread compound. Size designation: R ½, R ¾, R 1.

Sealing: PTFE tape applied to the male thread (3–5 wraps clockwise). The taper provides progressive tightening and a self-sealing joint.

Where used: UK domestic plumbing (traditionally), India, parts of Asia. Also used in some industrial applications where a taper seal is preferred over a face seal.

NPT — National Pipe Taper (American Standard)

The dominant standard in the United States, Canada, and much of Latin America. NPT uses a 60° included angle thread form (not 55° like BSP) with a 1:16 taper. Same nominal size designations (½", ¾", 1") but the different thread angle means BSP and NPT are not interchangeable.

Sealing: PTFE tape on the male thread, or anaerobic thread sealant (Loctite 545 or similar). The 1:16 taper creates a progressive wedge seal as tightening proceeds.

Identifying NPT vs BSP: The thread angle difference (60° vs 55°) is not visible to the naked eye, but the pitch is slightly different at each nominal size. The definitive check is a thread gauge. As a quick field test: a BSP thread gauge will not fully pass on an NPT thread, and vice versa.

Where used: USA, Canada, Mexico, and associated supply chains globally. Any equipment manufactured to American standards (pumps, compressors, industrial equipment, oil & gas) will typically have NPT threads.

NPTF — National Pipe Taper Fuel (Dryseal)

A variant of NPT with tighter tolerances designed to seal on the thread alone without sealant. Used in fuel, hydraulic, and refrigerant applications where contamination from thread sealants is unacceptable. Not interchangeable with standard NPT in terms of sealing performance, though dimensional compatibility allows initial assembly.

JIC — Joint Industry Council (SAE 37°)

A completely different beast — JIC is a flare fitting standard, not a pipe thread standard. A 37° flare is formed on the tube end, and a JIC nut with matching 37° seat compresses against it to create a metal-to-metal seal.

Thread designation: JIC uses straight (parallel) threads on the nut — not a pipe thread at all. The sealing happens at the 37° flare seat, not in the threads. Common sizes: -4 (¼"), -6 (⅜"), -8 (½"), etc. (dash numbers referring to tube OD in 1/16" increments).

Where used: Hydraulics, pneumatics, fuel systems, instrumentation. Any application where a mechanical flare seal is preferred over thread sealing. Common in aerospace, automotive, industrial hydraulics, and marine applications.

Do not confuse with SAE 45° flare: HVAC uses a 45° flare (SAE J513). JIC is 37°. These look similar but are not interchangeable. A 45° flare nut on a 37° seat will leak.

ORFS — O-Ring Face Seal

Not a thread-sealing system at all — ORFS uses an O-ring recessed into the face of the female fitting, which is compressed by the male fitting face on assembly. The threads (straight, parallel) only provide clamping force. Used extensively in hydraulics above 200 bar where JIC flares are not sufficient.

Quick Identification Reference

Ordering the Right Thread — Every Time

When placing an order, always specify all three of these:

1. Thread standard: BSPP, BSPT, NPT, JIC, etc.
2. Size: ½", ¾", 1" (or -4, -6 for JIC/hydraulic dash sizes)
3. Male or female

"½ inch male brass elbow" is ambiguous. "½" BSPT male × ½" BSPT male brass elbow" is a specification. The extra five seconds of precision prevents a very annoying wrong-thread situation on site.