Valve Basics

by DoItYourself Staff

Valves Safety Tips

Plastic valves should not be used in steam, gas or compressed air lines. However, valves can be used with hot and cold fluid systems.

Never over-tighten any valve, as you can strip the threads and ruin the valve.

Whenever turning on a main water supply valve that has been turned off, always be sure to turn the water on slowly to avoid water banging in the pipes.

When soldering copper pipe to a brass valve, always open the valve completely to avoid excessive heat damage.

Gate Valve

Uses a sliding wedge to move across the waterway, in either a rising or non-rising action.

Used to completely shut off or open a waterway. Does not control the volume of flow.

In some models, either opening of a gate valve may face the pressure side of the line, while in others, an arrow indicates the direction of water flow.

Because they allow the complete passage of water, use on supply lines that are in constant use.

A Connector Gate Valve uses a union fitting on one side

Boiler Drain Valve

A horizontal faucet with male hose threads on the outlet side and either male or female IPS threads on the inlet side.

Originally designed to drain water from a boiler, hence the name.

Today, they're usually used for laundry machine hookups.

Newer models of laundry valves have a single lever that controls the hot and cold water supply.

Ball Valve

Uses a large lever to turn a ball that closes or opens the flow of water with one quick quarter turn.

Are the standard for natural and LP gas, replacing the older plug valves that were traditionally used as gas valves.

Available in either metal or plastic, threaded or non-threaded types.

Ball valves with double-stem seals provide greater durability.

Globe Valve

Used when a valve must be opened and closed frequently under high water pressure.

Used to control volume of flow. These valves have two chambers with a partition between them for passage of water that must change course several times from port to port.

Should not be used in water supply lines for occasional shut-off purposes.

An angle valve is similar to a globe valve, but has its ports at right angles. Install at a turn in piping to eliminate the necessity of an elbow (this is often preferred to using a globe valve and elbow).

An angle valve has greater water passage than a globe valve. Since there is only one change in direction of flow, there is less resistance.

A Connector Globe Valve uses a union fitting on one side

Pressure Relief Valve

Used to protect water heaters or hot water storage tanks.

When the water pressure reaches a dangerous level, the valve opens and discharges water. Cold water then flows into the tank and stabilizes the water pressure

Stop & Waste Valve

Has a small opening on the non-pressure side to allow drainage when it is in cut-off position. Helps prevent freezing of water lines in winter.

Also known as a bleeder valve or drainable valve.

Comes in threaded, sweat, flare and slip joint ends. The latter two are municipal and emergency valves.

Flat head or socket head are common residential types have a socket head that takes a 3/8" key rod.

Check Valve

Operates automatically, permitting flow in one direction only.

Sometimes combined with a throttling or shut-off valve. Some communities require a check valve in cold water lines between the water heater and meter.

Used to prevent water pumped to an overhead tank from flowing back when the pump stops.

Some check valves are designed for use with vertical pipes only. Therefore, it will not work if installed upside down. The closing device is a disk, ball or clapper that falls shut by gravity when installed vertically.

Another variety is the Swing-Type check valve, which is a small, smooth swing-type gate located in the center of the valve. As water is pumped through the flow side of the valve, a gate swings open to allow water to pass. If water attempts to back up through the valve, the gate is forced shut against the pressure side of the valve.