Reducing Bush BSPT Male Female Thread Pipe Fitting – Stainless Steel 304 (A2)

Identify the female (larger) port size on your pipe or fitting, then select the male (smaller) outlet size you need to step down to. For example, a 1/2" Female – 3/4" Male bush reduces a 3/4" male pipe into a 1/2" female socket. BSPT sizes are typically expressed in inches: 1/8", 1/4", 3/8", 1/2", 3/4", 1", 1-1/4", and 1-1/2". If you are unsure, measure the outer diameter of the male thread and compare it to a BSPT thread chart — for example, a 1/2" BSPT male thread has an outer diameter of approximately 20.96mm (≈0.825").

These fittings use BSPT (British Standard Pipe Taper) threads, also known as R/Rc threads. BSPT is a tapered thread standard widely used in plumbing, hydraulics, and industrial piping across the UK, Europe, Asia, and Australia. It is generally not directly compatible with NPT (National Pipe Taper) threads used in North America without an adapter, as the thread angle differs (55° for BSP vs. 60° for NPT).

These reducing bushes are made from Grade 304 stainless steel, designated A2 under the ISO 3506 standard. Grade 304 contains approximately 18% chromium and 8% nickel, giving it good corrosion resistance in most indoor and mild outdoor environments, including exposure to water, steam, and many dilute chemicals. For highly aggressive environments such as direct saltwater immersion or chloride-rich atmospheres, Grade 316 (A4) is generally recommended.

Yes. Stainless steel 304 (A2) is generally suitable for outdoor and wet environments, including garden irrigation systems, outdoor compressed air lines, and industrial washdown areas. In most cases it will resist surface rust and corrosion far longer than zinc-plated or galvanized carbon steel fittings. For direct saltwater or coastal environments, Grade 316 stainless steel is typically the better choice.

Stainless steel BSPT reducing bushes in these sizes are typically rated for use in systems up to approximately 150 PSI (≈10 bar) under normal ambient conditions, though the actual rating depends on the specific size, wall thickness, and the media being conveyed. Always verify the pressure rating against your system requirements. For critical or high-pressure applications, contact us to confirm suitability or consult a qualified engineer.

Yes, in most cases. BSPT tapered threads are designed to seal progressively on the thread taper as the fitting is tightened, but applying PTFE tape (thread seal tape) or a suitable pipe thread sealant compound is generally recommended to ensure a leak-free connection, especially in pressurized water, air, or gas systems. Wrap PTFE tape clockwise (when viewed from the male thread end) for 2–3 turns before assembly.

BSPT (tapered) and BSPP (parallel, also called G threads) share the same thread pitch and nominal diameter, so they can often be assembled together in practice. However, a tapered-to-parallel combination does not seal on the thread taper alone and will require PTFE tape or a sealant compound. For critical pressure applications, using matched thread types (tapered-to-tapered or parallel-to-parallel with a face seal) is generally recommended.