* Valves, sill cocks and faucets control the water supply. Valves and sill cocks are used on pipelines; faucets are installed on fixtures.
Valves in home plumbing lines usually are cast bronze and have portions machined and threaded for trimmings.
* Gate valves have a sliding wedge that is moved across the waterway, usually by a threaded spindle or stem. It is either rising or non-rising, the latter having a shorter bonnet.
A gate valve is used to completely shut off or open a waterway, but not control the volume of flow. In some models, either opening of a gate valve may face pressure side of the line, while in others, an arrow indicates the direction of water flow.
Gate valves allow complete passage of water and should be used en supply lines that are in constant use.
* Globe and angle valves are used when a valve must be opened and closed frequently under high water pressure. Globe valves are used to control volume of flow. They have two chambers with a partition between them for passage of water that must change course several times from port to port. Globe valves 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. Water passage is greater than through a globe valve. Since there is only one change in direction of flow, less resistance occurs. An angle valve installed at a turn in piping eliminates the necessity of an elbow and is often preferred to using a globe valve and elbow.
* Plug and key valves are better known in the plumbing industry as straight stops. These have tapered ground plugs that seat into matched tapered ground bodies. Plugs have flat heads, square heads or socket heads; the other end is threaded to hold a hex nut and friction ring combination. This is mounted over a tension spring inside the body that keeps the plug tight. They are manufactured in brass, bronze, galvanized iron-bodied and black iron-bodied and are used mostly as gas stops.
* Drainable valves or stop and waste valves have a small opening on the non-pressure side to allow drainage when they are in the cut-off position. It is sometimes called a bleeder valve and may be obtained in threaded, sweat, flare and slip joint ends. The latter two are municipal and emergency valves. Most are flat head or socket head; common residential types have a socket head that takes a 3/8" key rod.
* Check valves operate automatically, permitting flow in one direction only. They are 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.
Check valves are 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, correct installation is essential. The closing device--a disk, ball or clapper--falls shut by gravity when installed vertically.
* Swing-type check valves serve the same purpose as check valves. A small, smooth swing-type gate is 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.
Plastic valves are made of CPVC, PVC and ACETAL. The plastic valves available are gate valves, universal line valves, straight supply valves, angle supply valves, washer hose valves, angle valves, sill cocks and ball valves.
* Ball valves have taken over the bulk of usage for natural and LP gas, replacing the older plug valves that were traditionally used as gas valves. Ball valves are available in both metal and plastic. Ball valves can be purchased both threaded and non-threaded. Ball valves with double-stem seals provide greater durability.
* One type of plastic valve is molded of ACETAL. It has threaded connections for use in metal piping systems. The other type, molded of CPVC or PVC, is either threaded or non-threaded with solvent-weld connections. These are used in plastic piping systems.
* Like plastic pipe fittings, solvent-weld valves (connections made by cement) must be used with compatible plastic piping systems; i.e., PVC valves used in a PVC piping system.
* Threaded-connection ACETAL valves, which can be used in most applications in which metal valves are used, are available in globe (stop), stop-and-waste, boiler drain, sill cock and sink faucet. Plastic valves should not be used in steam, gas or compressed air lines. However, valves can be used with hot and cold fluid systems.
The ACETAL valves perform at temperatures of -20[degrees]F to 180[degrees]F. They can withstand pressure up to 150 lbs. and are excellent for hard-water areas because they resist mineral build-up.
Solvent-weld CPVC and PVC valves offer similar benefits to the ACETAL valves. These are available in globe (stop) and boiler drains. Gate valves end ball valves are available in PVC and CPVC.
WATER SAFETY SYSTEMS
Leaks in plumbing systems can cause major damage to a house if left unchecked for long. An automatic water-shutoff valve that is designed to limit the damage caused when washing machine hoses rupture, icemaker supply lines crack and water supply lines freeze. This whole-house system is installed in the main water line after it enters the home. It consists of a water flow sensor and motor-driven ball valve installed in the water supply, which is monitored by an LCD controller mounted elsewhere in the home. The sensor inside the flow path tells the controller when water is flowing into the house at any given moment.
A similar automatic water-shutoff valve is a wireless system that also is installed into the main water line. It consists of a shutoff valve, receiver, transmitter and battery-powered sensors. The sensors are placed where leaks are likely to occur. When the sensors detect water, they automatically send a signal to the receiver to shut off the water.
Another type of safety valve system is designed specifically to prevent damage from ruptured washing machine hoses. The washing machine is plugged into the safety valve kit's control box, which is plugged into a standard outlet. The low-voltage valve system shuts off cold and hot water at the shutoff valves. The valves automatically open when the washing machine is turned on and close as soon as the machine shuts off. When valves are closed, the hoses are not under pressure and retain little water.
Safety Tips for Valves
** 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.