What Is a 3-Way Stopcock?

A 3-way stopcock is a small plastic valve used throughout clinical medicine to control the direction of fluid flow between three ports. It is one of the most widely used disposable medical devices in hospitals — found on IV lines, arterial lines, central venous catheters, and fluid delivery systems in nearly every ICU, operating room, and emergency department worldwide.

How a 3-Way Stopcock Works

The stopcock has a rotating handle — the lever — connected to an internal channel. By rotating the handle, the clinician selects which two of the three ports are connected and which is blocked. Common positions:

• Position A: Ports 1 and 2 open, Port 3 (side port) closed — main line flowing, side port capped
• Position B: Ports 2 and 3 open, Port 1 closed — side port medication injected into downstream line
• Position C (OFF): All ports closed — stops flow for sampling or line manipulation

The handle is marked with directional arrows and "OFF" to show which port is blocked. Most clinical stopcocks use a four-pointed star or arrow handle design for easy manipulation with one hand while wearing gloves.

Luer Lock vs Luer Slip Stopcocks

All 3-way stopcocks connect to IV tubing, syringes, and catheter hubs via Luer connections. There are two types:

• Luer lock: A threaded collar on the port that screws onto compatible fittings and locks in place. Prevents accidental disconnection under pressure. Required for arterial lines, high-pressure contrast injection, and any application where disconnection would cause harm.
• Luer slip (friction fit): The tapered tip inserts into a matching bore and holds by friction. Faster to connect and disconnect. Used where accidental disconnection is less critical — peripheral IV lines, simple fluid administration.

For a complete comparison, see our guide: Luer Lock vs Luer Slip — When to Use Which.

Clinical Applications

• IV drug administration: Allows medication bolus or continuous infusion without disconnecting the main IV line. The most common stopcock use.
• Arterial line management: Connects pressure transducer while allowing blood sampling and line flushing from a single catheter access point.
• Central venous catheter: Multi-lumen access for simultaneous drug delivery and pressure monitoring.
• Contrast media injection: High-pressure stopcocks used between power injector and IV access for CT and MRI contrast administration. These require specifically rated high-pressure versions.
• Hemodynamic monitoring: Pressure transducer connection for CVP, PAP, and PCWP measurement in the ICU.

Standard vs High-Pressure Stopcocks

Feature	Standard Stopcock	High-Pressure Stopcock
Pressure rating	Standard IV pressure	Power injector rated
Connection	Luer lock or Luer slip	Luer lock only
Body material	Medical-grade PC	High-clarity reinforced PC
Applications	IV therapy, CVP monitoring	CT, MRI, angiography contrast
Air visualization	Clear body	Full transparency — critical for contrast

What to Specify When Ordering Custom Stopcocks

If you are ordering custom stopcocks for OEM use, the key specifications to define are:

• Connection type: Luer lock or Luer slip on each port
• Pressure rating: Standard or high-pressure (power injector rated)
• Handle color: Clinical color coding or brand colors
• Port orientation: Standard T-configuration or custom angles
• Extension tube: Integrated or separate
• Branding: Company name/logo on body or handle
• Sterilization: EO sterilization packaging required or bulk supply