Male‑Female Threaded Coupling

Every time a pipe needs to pass through a tank wall, a panel, or a bulkhead, the same problem appears: how to get through without leaking.

• Drill a hole → water leaks around the pipe
• Use sealant → it dries, cracks, and fails
• Use a bulkhead fitting → the correct solution

A bulkhead fitting is a specialized pipe fitting that mounts through a pre-drilled hole and seals against the wall using rubber gaskets. One end connects to the pipe inside the tank; the other connects to the pipe outside.

No sealant required. No welding. Simple installation.

Yunnl bulkhead fitting is a male-female threaded connector designed for through-wall and through-tank pipe penetration. The fitting passes through a pre-drilled hole in a tank wall, panel, or bulkhead. EPDM rubber gaskets on both sides of the wall are compressed by a locking nut, creating a static seal that prevents fluid leakage.

One end of the fitting has a male thread for connection to female-threaded pipes or fittings. The opposite end has a female thread for connection to male-threaded pipes or fittings.

The fitting is machined from forged H59 brass and includes EPDM sealing gaskets. No additional sealants or tapes are required for the bulkhead seal.

• Components

• The Sealing Principle

1. The fitting body is inserted through a pre-drilled hole in the wall
2. EPDM gaskets are placed on both sides of the wall
3. The locking nut is tightened
4. Gaskets are compressed against the wall surface
5. Compression creates a static seal - no fluid passes through the wall gap
6. Pipes connect to both ends of the fitting

• Key Design Feature

The sealing is independent of the pipe connections. The gaskets seal against the flat wall surface, not against the pipe threads. This means:

1. The wall seal does not depend on thread tape or sealant
2. The fitting can be disassembled and reassembled
3. Pipe connections and wall seal are separate - less risk of leakage

Classification by Thread Position

Single-Threaded Connector: Only one end is threaded (internal or external), with the other end being a plain pipe or a welded interface, used for straight pipe extension or equipment connection.

Double-Threaded Connector: Both ends have internal and external threads respectively, enabling "male-female" conversion to adapt to different thread specifications.

Classification by Functional Expansion

Reducing Internal and External Threaded Connectors: Thread specifications at both ends are different (e.g., one end is 1/2" internal thread, the other end is 3/4" external thread), used for adjusting pipe diameters.

Combination Connectors: Integrate functional modules such as right-angle elbows and tees to simplify complex pipeline layouts.

• Water Storage Tanks

Use case: Inlet and outlet connections on water storage tanks.
Installation: Bulkhead fitting passes through the tank wall. Inside connects to the tank outlet pipe; outside connects to the building supply line.
Value: Clean, leak-free penetration. Easy to install and service.

• Water Treatment Equipment

Use case: Connections on filter housings, softener tanks, and chemical dosing tanks.
Installation: Bulkhead fitting mounts on the equipment wall. Pipes connect on both sides.
Value: Reliable seal for chemical and water applications. EPDM gaskets resist chemicals.

• Plumbing Through-Wall Installations

Use case: Pipes passing through walls in residential and commercial plumbing.
Installation: Fitting mounts in the wall. Interior pipe connects to one end; exterior pipe connects to the other.
Value: Clean, finished wall penetration. No gaps or exposed holes.

• Solar Water Heating Tanks

Use case: Connections on solar storage tanks.
Installation: Bulkhead fitting on the tank wall for collector supply and return lines.
Value: High-temperature compatibility. Reliable seal for circulating water.

• Agricultural Irrigation Tanks

Use case: Water storage and fertigation tank connections.
Installation: Bulkhead fitting on tank walls for supply and outlet lines.
Value: Corrosion resistance for outdoor and agricultural environments.

• Light Industrial Fluid Systems

Use case: Process tanks, mixing vessels, and storage vessels.
Installation: Bulkhead fitting for inlet, outlet, and drain connections.
Value: Chemical resistance (EPDM). Reliable seal for non-corrosive fluids.

• Pre-Installation Check

• Installation Steps

1. Drill the hole – Drill a clean hole in the tank wall or panel at the correct diameter
2. Deburr the hole – Remove burrs and sharp edges that could damage the gaskets
3. Insert the fitting – Push the fitting through the hole from the inside (or outside)
4. Install the inner gasket – Place the gasket over the fitting body on the inside of the wall
5. Install the outer gasket – Place the gasket over the fitting body on the outside of the wall
6. Thread the locking nut – Screw the locking nut onto the fitting body from the outside
7. Hand-tighten – Tighten the nut by hand until the gaskets contact the wall
8. Final tightening – Use a wrench to tighten further, compressing the gaskets
9. Connect pipes – Attach pipes to both ends using PTFE tape
10. Test – Fill the tank and check for leakage

• Torque Guidelines

• Important Notes

1. Do not over-tighten – Brass threads can crack
2. Do not use sealant on the wall seal – The gaskets provide the wall seal
3. Use PTFE tape on pipe threads – Standard thread sealing practice
4. Flat surface required – The gaskets need a flat surface to seal correctly
5. Check gasket position – Gaskets must be seated squarely against the wall