Custom Thread Adapters for Hydraulics, Plumbing and Water Lines – NPT, BSPP, M22 and M24 Explained

Why hydraulic and plumbing threads often do not fit

Many pipe and machine threads look almost identical at first glance. In practice, they may differ in nominal diameter, pitch, flank angle, taper, thread depth and sealing method. A small difference is enough to prevent proper engagement or create a connection that appears to fit but is mechanically incorrect.

This problem is common with imported pumps, valves, pressure gauges, filters, CNC machines, agricultural equipment, laboratory systems, faucets, radiator valves and replacement components. North American equipment often uses NPT threads, while European systems frequently use BSPP, BSPT or metric fine threads.

A custom thread adapter bridges the gap without replacing the complete valve, faucet, pump or assembly.

The American pipe thread problem

One of the most frequent compatibility issues is the use of NPT, short for National Pipe Taper. NPT is widely used on American pipe, hydraulic and pneumatic components.

In Europe and many other regions, the British Standard Pipe family is more common. A frequent variant is BSPP, also known as a parallel G thread.

NPT and BSPP can look similar, especially in smaller sizes. They are not interchangeable.

Key differences between NPT and BSPP

• NPT: tapered pipe thread with a 60° thread angle.
• BSPP: parallel Whitworth pipe thread with a 55° thread angle.
• Pitch: the number of threads per inch may differ depending on size.
• Sealing: NPT commonly seals through thread interference, while BSPP usually requires a washer, bonded seal, O-ring or separate sealing face.

Forcing an NPT male thread into a BSPP female thread can damage both parts, misalign the connection and cause leaks. The same applies in the opposite direction.

The solution: the HydraLink NPT–BSPP adapter

The HydraLink NPT–BSPP Male Thread Adapter is designed for custom transitions between American and British-style parallel pipe threads.

Both connection sides can be selected independently, which makes it possible to create:

• NPT to BSPP adapters
• BSPP to NPT adapters
• NPT to NPT adapters
• BSPP to BSPP adapters
• reducers between different nominal sizes
• custom male-to-male pipe thread adapters

The online model automatically generates the hexagonal wrench section, external dimensions and continuous flow channel from the selected parameters. Adjustable settings include thread A, thread B, body length, wall thickness, thread clearance, bore safety clearance and lead-in chamfer.

Metric plumbing threads: M22, M24 and other common sizes

Thread compatibility problems are not limited to NPT and BSPP. Faucets, tap aerators, flow regulators and radiator valves often use metric fine threads.

Common search queries include:

• M22 to M24 adapter
• M24 to M22 adapter
• faucet aerator adapter
• tap thread adapter
• male to female plumbing adapter
• female to female thread coupler
• M30×1.5 radiator valve adapter

For these applications, use the custom M18–M30 metric plumbing thread adapter.

Supported metric thread sizes

• M18×1
• M20×1
• M22×1
• M24×1
• M28×1
• M30×1.5

Both ends can be configured independently as male or female. This allows you to create M24-to-M22 aerator adapters, male-to-female reducers, double-male nipples, female-to-female couplers and custom transitions for older or manufacturer-specific plumbing parts.

Which adapter should you choose?

Choose the HydraLink NPT–BSPP adapter when:

• an American NPT fitting must connect to a European BSPP G thread;
• you need two independently selectable NPT or BSPP male threads;
• the standard adapter you need is not available locally;
• you are working with imported machinery, pumps, valves or instruments.

Choose the metric plumbing adapter when:

• you need an M22-to-M24 or M24-to-M22 faucet adapter;
• you are connecting a tap aerator or flow regulator;
• you need male, female or mixed metric thread ends;
• you are adapting an M18, M20, M22, M24, M28 or M30×1.5 connection.

How to identify and measure an unknown thread

Correct identification is essential before configuring any adapter. Never rely only on visual appearance.

1. Measure the major diameter

Use calipers to measure the largest outside diameter of a male thread. For female threads, the visible bore can provide an initial indication, but it does not directly equal the nominal size.

2. Determine the pitch

Metric thread pitch is specified in millimetres. For example, M24×1 means a nominal diameter of 24 mm and a pitch of 1 mm.

NPT and BSP threads are normally identified by nominal pipe size and threads per inch. A thread gauge is the safest tool for distinguishing similar profiles.

3. Check whether the thread is tapered or parallel

NPT becomes narrower along its length. BSPP and metric plumbing threads are generally parallel. Measuring the diameter at two positions can help identify taper.

4. Identify male or female thread

A thread on the outside of a fitting is male. A thread inside a bore, nut or socket is female.

5. Measure the available engagement length

A thread can have the correct diameter and pitch but still fail because it bottoms out before reaching the sealing face. Measure the usable thread depth on both components.

6. Identify the sealing method

Determine whether the joint seals through tapered thread contact, a flat washer, O-ring, bonded seal, cone or face seal. A thread adapter does not automatically replace the required seal.

Configure the adapter directly in your browser

The parametric configurators generate the complete adapter from your inputs. No CAD knowledge is required.

Depending on the selected model, you can adjust:

• thread standard and nominal size
• male or female thread type
• thread length on both ends
• hex width and body length
• wall thickness
• internal flow bore
• 3D-print thread clearance
• lead-in chamfers
• bore safety clearance

The 3D preview updates in the browser, allowing you to check proportions and overall dimensions before downloading or ordering.

Download the STL or order the adapter printed

Print the adapter yourself

If you own a 3D printer, you can use the configured STL in Bambu Studio, Cura, PrusaSlicer or another slicer. Review orientation, wall count, layer height, material, dimensional compensation and thread clearance before printing.

Have the adapter printed by BuildYour3D

You can also order the configured adapter as a finished 3D-printed part. This option is useful for repairs, workshops, prototypes and custom machine connections when no suitable printer is available. Typical production and delivery time is approximately three business days.

Which material is suitable for a custom plumbing or hydraulic adapter?

• PLA: useful for fit checks, display models and dry low-load applications.
• PETG: tougher and more moisture-resistant than PLA; a practical choice for many functional prototypes.
• ASA: more suitable for outdoor use because of improved UV and weather resistance.
• ABS: robust and more temperature-resistant than PLA, but more demanding to print.
• Engineering filaments: nylon and fibre-reinforced materials may be suitable for specific applications after proper validation.

Material choice alone does not make a part pressure-rated. Wall thickness, print orientation, layer bonding, temperature, chemical compatibility and safety factor also matter.

Are 3D-printed hydraulic adapters pressure-safe?

A 3D-printed adapter is not automatically a certified hydraulic, pneumatic, potable-water or pressure fitting. FDM parts may fail through layer separation, porosity, creep, stress concentration or impact.

For high pressure, pulsating pressure, hot fluids, hazardous media or safety-critical systems, use certified metal or industrial fittings. Configurable printed adapters are best suited for prototypes, fit checks, fixtures, demonstrations, low-pressure applications and individually tested projects.

Typical applications

• faucets and tap aerators
• water filters and flow regulators
• irrigation and garden systems
• radiator valves
• pumps and pressure gauges
• laboratory and test rigs
• pneumatic prototypes
• hydraulic demonstrators
• imported machinery and spare parts
• agricultural equipment and classic vehicles
• CNC machines and workshop equipment
• repairs and custom engineering projects

FAQ: custom hydraulic and plumbing thread adapters

Can NPT and BSPP be screwed together directly?

No. NPT and BSPP differ in thread angle, taper, pitch and sealing method. Use a correctly designed NPT-to-BSPP adapter.

What is the difference between NPT and BSPP?

NPT is a tapered American pipe thread with a 60° profile. BSPP is a parallel Whitworth pipe thread with a 55° profile and is often called a G thread.

Is BSP the same as BSPP?

BSP is a thread family. BSPP is the parallel version, while BSPT is the tapered version. They should not be treated as identical.

Can I configure an M24-to-M22 faucet aerator adapter?

Yes. Set one side to M24×1 and the other to M22×1, then choose male or female independently to match the faucet and aerator.

Which metric plumbing threads are supported?

The metric configurator supports M18×1, M20×1, M22×1, M24×1, M28×1 and M30×1.5.

Can I create a male-to-male adapter?

Yes. HydraLink creates NPT/BSPP male-to-male variants. The metric model can also be configured with male threads on both ends.

Can I create a female-to-female coupler?

Yes. The metric plumbing model allows both ends to be configured as female threads.

How do I know whether my faucet thread is M22 or M24?

Measure the major diameter with calipers and check whether the faucet or aerator has a male or female thread. Manufacturer variations exist, so always verify the actual part.

How do I identify an unknown pipe thread?

Measure diameter, pitch and taper, identify male or female form and compare the result with an NPT, BSPP, BSPT or metric thread chart. A thread gauge is strongly recommended.

Is a 3D-printed thread adapter watertight?

Not automatically. FDM parts can leak between layers, and the thread alone may not provide a reliable seal. Use the correct washer, O-ring or sealing face and perform a controlled leak test.

Can I download the STL?

Yes. After configuration, the generated model can be used for STL download and self-printing.

Can I order the adapter already printed?

Yes. You can order the configured part as a finished 3D print. Typical production and delivery time is approximately three business days.

Is the adapter suitable for high-pressure hydraulics?

It is not automatically certified for high pressure. Use approved industrial fittings for high, pulsating or safety-critical pressure systems.

Can the adapter be used with drinking water?

Potable-water suitability depends on the material, manufacturing process, local regulations and hygiene requirements. A standard printed part should not be assumed to be approved for drinking water.

Do I still need a seal?

Usually yes. BSPP and metric plumbing connections often require a flat washer, O-ring or other defined seal. NPT may require an appropriate thread sealant depending on the application.