Internal Reducing Unions

Valco internal reducing unions are engineered to connect two different tubing sizes while maintaining true zero-dead-volume flow paths on both ends. These precision fluidic connectors enable controlled transitions between tubing IDs, helping minimize turbulence and preserve chromatographic performance in HPLC and analytical systems.

Bulkhead versions feature the bulkhead nut on the smaller tubing side, providing proper panel mounting orientation and secure installation in instrument enclosures or brackets.

Standard material is 300 series stainless steel. Optional materials include Hastelloy C, gold-plated stainless steel, and titanium for chemically aggressive environments, inert flow paths, or specialized applications.

For best results, select the union with a bore that matches your tubing ID. When connecting tubing with different internal diameters, always choose the bore that matches the smaller tube ID to reduce dispersion and maintain separation efficiency.

TUBING OD BORE PART NUMBER
1/16" to 1/32"0.15 mmZRU1.5XC
1/16" to 1/32"0.25 mmZRU1.5
1/16" to 1/32"0.50 mmZRU1.5L
1/16" to 1/32"1/32"ZRU1.5T
1/8" to 1/32"0.25 mmZRU2.5
1/8" to 1/32"0.50 mmZRU2.5L
1/8" to 1/32"1/32"ZRU2.5T
1/8" to 1/16"0.25 mmZRU21C
1/8" to 1/16"0.75 mmZRU21
1/8" to 1/16"1/16"ZRU21T
1/4" to 1/16"1/16"ZRU41T
1/4" to 1/8"1.0 mmZRU42
Key Definitions â–¶
Internal Reducing Union
A zero-dead-volume connector that joins two different tubing sizes, using internal fittings on each end to maintain a controlled flow path.
Zero Dead Volume (ZDV)
A connection design that minimizes void spaces between tubing and fittings, helping reduce band broadening and preserve chromatographic efficiency.
Tubing ID
The internal diameter of tubing. Reducing unions should be selected with a bore that matches the tubing ID whenever possible.
Bore
The internal passage diameter through the union. When tubing IDs differ, matching the bore to the smaller tubing ID helps minimize dispersion and turbulence.
Bulkhead Version
A panel-mount configuration designed for installation through an instrument wall or bracket. For Valco reducing unions, the bulkhead nut is on the smaller tubing side.
Material Options
Standard construction is 300 series stainless steel, with optional Hastelloy C, gold-plated stainless, and titanium for aggressive, inert, or specialized applications.
Frequently Asked Questions â–¶
What is a Valco internal reducing union?
A Valco internal reducing union connects two different tubing sizes while maintaining true zero-dead-volume flow paths on both ends, helping preserve chromatographic performance.
How do I choose the correct bore size?
Select the union with a bore that matches your tubing ID whenever possible. If tubing IDs differ, choose the bore that matches the smaller tubing ID to minimize dispersion and turbulence.
Where is the bulkhead nut located on reducing unions?
On bulkhead versions, the mounting nut is positioned on the smaller tubing side to ensure proper panel orientation and secure installation.
What materials are available for Valco internal reducing unions?
Standard construction is 300 series stainless steel. Optional materials include Hastelloy C, gold-plated stainless, and titanium for aggressive solvents, inert flow paths, or specialized applications.
Are Valco internal reducing unions suitable for HPLC and UHPLC?
Yes. These unions are designed for high-pressure chromatography environments and are commonly used in HPLC and UHPLC systems where zero-dead-volume connections are critical.