Press Fittings (ProPress): Definition & Technical Guide
Call Now (855) 557-9600
Press fittings, widely known by the Viega brand name ProPress, are a flameless copper and stainless steel pipe joining system that uses a hydraulic pressing tool to permanently deform a fitting around the pipe end, compressing an internal EPDM or HNBR O-ring to create a watertight and gas-tight seal in seconds. Press fittings eliminate the need for soldering, brazing, or threading, reducing installation time by up to 60 percent compared to traditional sweat connections.
Hydraulic Pressing, EPDM O-Ring Seal & Smart Connect Safety Feature
The press fitting system consists of three components: the fitting body (copper or stainless steel with an integrated sealing element), the pipe (standard copper tube or stainless steel), and the pressing tool. The plumber cuts the pipe to length, deburs the end, marks the insertion depth, slides the fitting onto the pipe, and applies the pressing tool. The tool’s jaws close around the fitting and compress it with approximately 32,000 pounds of force, permanently deforming the fitting onto the pipe and compressing the O-ring into a precise seal.
The entire press cycle takes 4 to 7 seconds per joint. Because no open flame is involved, press fittings can be installed in occupied buildings, near combustible materials, and in confined spaces without hot work permits. This safety advantage makes press fittings particularly valuable for repair work in finished homes where soldering risks fire damage to wall cavities and insulation.
A built-in safety feature of press fittings is the Smart Connect design. If a fitting is accidentally left unpressed, water pressure during system pressurization causes the unsealed O-ring to leak immediately, alerting the plumber to the missed connection before the system is concealed behind walls. This prevents latent leak failures that might not appear for weeks or months.
Copper Press, Stainless Steel, Gas-Rated & PEX Transition Types
Copper press fittings are used with standard Type K, L, and M copper tube from 1/2 inch to 4 inches in diameter. They are approved for potable water, hydronic heating, and chilled water systems.
Stainless steel press fittings are used in corrosive environments, food service, medical gas, and marine applications where copper is not suitable. They use Type 304 or 316L stainless steel pipe.
Press x thread transition fittings connect pressed copper or stainless steel to threaded steel, brass, or iron pipe. These are essential for integrating press systems into existing threaded infrastructure.
Press x PEX transition fittings connect pressed copper to PEX tubing at transition points, commonly used where copper stub-outs in walls connect to PEX distribution systems.
Gas-rated press fittings use a yellow-dot identification system and HNBR sealing elements rated for natural gas and propane service. Standard water-rated press fittings with EPDM O-rings are not approved for gas.
Repiping, Water Heater Replacement & Emergency Leak Repair Services
Bonded Plumbworks’ technicians use press fitting technology for copper pipe installations where speed, safety, and reliability are priorities. During repiping projects in occupied homes, press fittings allow the team to make connections without open flame, reducing fire risk and eliminating the need for fire watches. For water heater replacements, press fittings streamline the copper connections between the heater and the existing distribution system.
Press fittings are also valuable for emergency leak detection repairs where speed minimizes water damage. A corroded or failed copper joint can be cut out and replaced with a press coupling in minutes rather than the extended setup time required for soldering.
ASTM F3226, ASME B16.51, NSF/ANSI 61 & ICC-ES ESR-1856
ASTM F3226 covers press-connect copper and copper alloy fittings. The applicable state building codes permits press fittings for potable water, gas (with appropriate rated fittings), and hydronic systems. NSF/ANSI 61 certification is required for fittings in potable water contact. ASME B16.51 covers copper press fittings for use with copper tube. Viega ProPress fittings carry ICC-ES evaluation reports (ESR-1856) confirming code compliance.
Viega, NIBCO, Apollo & Milwaukee Tool Press Systems
Viega manufactures the ProPress system for copper and MegaPress for steel and stainless steel. NIBCO produces the Press System for copper tube in sizes up to 4 inches. Elkhart Products (Apollo) offers theDERA press fitting line. Milwaukee Tool and RIDGID both manufacture battery-powered pressing tools compatible with multiple fitting brands.