Full Port vs Standard Port Ball Valve

Quick Answer

A full port (full bore) ball valve has a bore diameter equal to the pipe inner diameter, creating no flow restriction. A standard port (reduced bore) ball valve has a bore one size smaller than the pipe, creating a slight restriction. Full port valves are required for pigging, low-pressure-drop services, and pipeline applications per API 6D. Standard port valves are acceptable for most process piping where a small pressure drop is tolerable.

Details

In a full port ball valve, the ball bore matches the nominal pipe size. A 6” full port ball valve has a 6” diameter bore through the ball. When fully open, the valve creates essentially zero additional pressure drop beyond the straight pipe equivalent.

In a standard port (also called reduced port or reduced bore) ball valve, the ball bore is typically one pipe size smaller than the nominal valve size. A 6” standard port ball valve has a bore of approximately 4” to 5”, depending on the manufacturer. This creates a venturi-like restriction that increases pressure drop and flow velocity through the valve.

Comparison Table

Parameter	Full Port	Standard Port (Reduced Bore)
Bore diameter	Equal to pipe ID	One size smaller than nominal
Pressure drop	Negligible (equivalent to straight pipe)	Higher (restriction effect)
Flow velocity through valve	Same as pipe	Higher (smaller bore)
Pigging	Yes (pig passes through)	No (pig cannot pass)
Erosion risk	Low	Higher (increased velocity at bore)
Ball and body size	Larger	Smaller
Weight	Heavier	Lighter
Cost	~15-25% more than standard port	Baseline
Standards	API 6D (pipeline), API 608	API 608
Typical applications	Pipelines, pigging lines, low-pressure-drop services	Process piping, utility, instrument root
Face-to-face	Same (per ASME B16.10)	Same (per ASME B16.10)

When to Specify Full Port

Full port is required or recommended in the following cases:

• Pipeline service per API 6D: all pipeline ball valves must be full bore to permit pigging and scraping operations.
• Low-pressure-drop requirement: systems where any additional pressure drop is unacceptable (e.g., flare headers, gravity flow lines).
• Erosive or abrasive service: full bore reduces flow velocity through the valve, minimizing erosion on the ball and seats.
• Measurement stations: valves upstream and downstream of flow meters where bore changes create turbulence and affect measurement accuracy.
• Large-diameter lines: the pressure drop penalty of a reduced bore increases with size and flow rate.

When Standard Port Is Acceptable

Standard port ball valves are suitable for:

• General process piping where a small pressure drop is tolerable
• Utility services (air, water, nitrogen)
• Instrument root valves and small-bore isolation
• Applications where cost and weight savings matter and pigging is not required

Pro Tip

On pipeline projects, always verify that the ball valve bore matches the pipeline ID, not just the nominal pipe size. Different pipe schedules have different IDs. A “full bore” valve based on Schedule 40 ID will restrict flow in a Schedule 20 (thinner wall) pipeline. Confirm the bore specification on the valve datasheet against the actual pipe schedule.

Both full port and standard port ball valves are rated per ASME B16.34 for pressure-temperature performance.

Read the full guide to valve types