Valve: Definition & Technical Guide
Call Now (855) 557-9600
A valve is a mechanical device installed in a plumbing system to control, regulate, or stop the flow of water, gas, or other fluids through a pipe by opening, closing, or partially obstructing the flow passage. Valves are present at nearly every connection point in a residential plumbing system, from the main water shutoff at the meter to individual fixture supply stops, making them the primary means of flow control in all plumbing installations.
Movable Element, Valve Body & Flow Control Mechanism Principles
Valves function by positioning a movable element, such as a disc, ball, gate, or diaphragm, relative to a stationary seat within the valve body. When the element is fully retracted from the seat, the valve is open and fluid flows freely. When the element seats firmly against the opening, the valve is closed and flow stops. Partial positioning allows the valve to throttle flow, though not all valve types are designed for throttling service.
The selection of valve type depends on the application: full-port ball valves provide unrestricted flow for main shutoffs, gate valves serve isolation duty in distribution lines, check valves prevent backflow, and pressure-reducing valves regulate downstream pressure. Each type has specific advantages and limitations that dictate where it should and should not be installed.
In a typical residential home, valves are found at the water meter, the main house shutoff, each branch line takeoff, every fixture supply (hot and cold), the water heater inlet and outlet, irrigation system zones, and the hose bibs. A single-family residence may contain 20 to 40 individual valves, all of which must function reliably to allow isolation of any section of the plumbing system for repair or emergency shutoff.
Ball, Gate, Globe, Check & Pressure-Reducing Valve Types
Ball valves use a spherical ball with a bore through the center. A quarter-turn of the handle rotates the ball between open and closed positions. Ball valves provide full-port flow with minimal pressure drop and are the preferred shutoff valve for residential plumbing.
Gate valves use a wedge-shaped gate that slides perpendicular to the flow. These are designed for fully open or fully closed operation and should not be used for throttling, as partial opening causes the gate to vibrate and wear.
Globe valves route flow through an S-shaped path and use a disc that moves perpendicular to the seat. The design creates significant pressure drop but allows precise flow regulation, making globe valves suitable for throttling applications.
Check valves allow flow in one direction only and close automatically when flow reverses. Swing check, spring check, and dual-check configurations serve different backflow prevention needs.
Pressure-reducing valves (PRVs) automatically reduce incoming water pressure to a set downstream pressure, protecting fixtures and piping from damage caused by excessive pressure.
Shutoff Valve Replacement, Backflow Prevention & Leak Isolation Services
Valve replacement, repair, and installation are core plumbing services. A failed shutoff valve can prevent isolation of a leak, turning a minor repair into an emergency. Bonded Plumbworks provides valve services across multiple categories, including leak detection and repair for failed valves, water line services for main shutoff valve replacement, and backflow prevention for check valve and RPZ device installation.
Bonded Plumbworks’ plumbers recommend that homeowners know the location of their main shutoff valve and verify it operates smoothly at least once per year. A seized main valve discovered during an active leak creates an urgent situation that requires the water utility to shut off supply at the meter.
NSF/ANSI 61, 372, ASSE 1003, 1015 & MSS SP-110 Valve Standards
Valves in potable water systems must comply with NSF/ANSI 61 for materials in contact with drinking water and NSF/ANSI 372 for lead-free content (less than 0.25 percent weighted average). The State building codes reference ASSE 1003 for water pressure-reducing valves and ASSE 1015 for double-check backflow prevention assemblies. Ball valves must meet MSS SP-110 or ASTM F1970 standards.
Watts, SharkBite Push-Fit, Nibco, Zurn Wilkins & Apollo Product Lines
Watts manufactures a full line of residential valves including ball valves, PRVs, and backflow preventers. SharkBite produces push-fit ball valves for tool-free installation on copper, PEX, and CPVC. Nibco offers lead-free brass ball valves and gate valves for potable water service. Zurn Wilkins manufactures backflow prevention assemblies and pressure-reducing valves.