What is a Plumbing Valve and What are Their Applications

The plumbing valve, it’s simplest definition is any valve used to regulate the flow of water in a potable or human waste water system. Pretty simple right? We suppose the the basic premise of a plumbing valve is simple but the types of valves and the broad range of applications are anything but simple. In the next few paragraphs we will give you each type of plumbing valve and it’s applications.

Angle Valve or Stop

Angle stops are named because they are manufactured at a 90 degree angle, they are used as shut off valves at the water intake of plumbing fixtures or appliances. They usually have an oval handle or can have a removable handle when vandalism or theft is an issue. In the past the angle stop needed to be rotated many times to ensure a complete water shut of, now most manufacturers make a 1/4 turn valve so the water can be shut off quickly in case of emergency.

Angle Valve or Stop

We’ll give you one emergency everyone has experienced that will make the 1/4 turn valve extremely valuable. Have you ever had a toilet backup and seen your toilet water level rising ever so slowly maybe you notice a floater or two and you couldn’t turn the angle valve fast enough to turn the water off? If you only had a 1/4 turn to close the valve off and that rising water would stop. The angle valve is not meant for high pressure applications. The type of connections used for angle stops are sweat, threaded and compression connections.

Gate Valve

The gate valve is a very old valve design. It is still used everyday on large diameter piping, in high pressure applications and in application where a valve is needed for a complete shut down. The gate valve is typically operated by a wheel handle and that handle lifts and lowers a metal disc or wedge cutting off or opening the flow of water. A gate valve should not be used to throttle or regulate the flow of water.

Gate Valve

When a gate valve is left partially opened water tends to rattle the mechanism inside eventually wearing out the seats and seals. Gate valves are usually described as rising stem sometimes called an OS&Y (Outside Screw and Yoke) or non-rising stem. An OS&Y valve allows you to see whether or not the gate valve is either open or closed because the stem rises outside the valve body. Non-rising stem gate valves are used in areas where space is an issue. The type of connections commonly used to connect a gate valve to the piping are threaded, flanged and sweat connections.

Check Valve

A check valve is a one way valve in that is has one inlet and one outlet that allows the a liquid to travel in one direction. It is used to halt the flow of the aforementioned liquid in case of a drop in pressure or reverse in directional flow. The majority of check valves used in the plumbing industry work automatically meaning when the pressure or direction changes the valve slams shut. One example of a check valve that is easy to understand is a backwater valve used on a sewer main as it leaves a residential or commercial building.

Check Valve

It’s main function is to close of the sewer in case the city main can’t handle storm water. If the city sewer runs full the only place for the water to go are the buildings connected to it, the valve keeps the water from coming back into the building. These valve can have a manual handle to close the valve, this is especially useful when leaving the residence or building unattended. The only problem is you have to remember to open it back up, you can imagine the mess if you use the toilets, lavatories etc. with no way for the waste to get out.

Backwater Check Valve

This valve works just like the above. It is a one way valve that is used most often in residential applications They are made by several manufacturers and they are basically heavy duty check valves. They are installed on the main sewer right at the foundation wall. They come in a check valve style in that when water starts backing up into the sewer line the valve slams shut or in a manual style.

Backwater Valve

If a home owner chooses a manual style back water valve they have to crank the valve shut during heavy rains and remember to open it back up when the rain is over because if someone uses the facilities while the valve is closed you will have some serious backups. Advantages of having a backwater valve, they work and they work well. Disadvantages, they aren’t cheap to buy or install.

Ball Valve

The ball valve is the most popular and widely used type of valve in the plumbing industry. It is built using a spherical disc or ball with a hole in it. When the ball is turned to the open position the hole or port is lined up with the flow of liquid letting it pass through. When the “ball” is turned to the closed position the port is perpendicular to the flow of liquid cutting off the opening. It’s early history is a little vague but here are couple known facts, the first ball type valve was patented by John Warren and issued to both Warren and John Chapman the founder of Chapman Valve Co. It was a manufactured out of brass with a brass ball and seats. The valve became an afterthought and was not mentioned in the Chapman literature.

Ball Valve

The next mention of the ball valve and the first resilient seated ball valve was developed and patented by Crane Company in 1945 (Resilient Seat – this is a real basic definition but you’ll get the idea, this is a non metallic seat that is resistant to oils, water and hydraulic fluids, has very good strength and works well in a broad spectrum of temperature ranges so it is resistant to expansion and contraction. Some examples of resilient seating materials are Neoprene, Buna-N and EPDM.) but like their historical predecessor Crane could not find a use for the valve.

Wafer Check

A wafer style check valve is obviously a check valve that is used when space constraints won’t allow traditional check valves to be used. Some of the other benefits of using a wafer check is weight, this style of check doesn’t need as much support as it’s traditional full body counterpart.

Ball Valve Cut-Away

A wafer valve is made using a thin disc that can be fastened in the center or the top or can be spring loaded in the center. This valve is meant to placed between two flanged fittings and secured between the two fittings with all thread rod. The valve is notched in the same positions as the bolt pattern of the flanges so the rod can pass by the valve. The valve is secured at both ends by the flanges.

Butterfly Valve

The butterfly valve has some similar features to that of the above wafer check valve. It is very thin and lightweight so space and support are not issues. It is closed using a wafer or disc that is mounted on a rod that is secured in the middle of the valve. The rod exits the valve at the top and ends with a handle that incrementally controls the internal disc.

Butterfly Valve

In the open position the disc is parallel to the pipe in the closed position the disc is perpendicular to the pipe closing off flow. These types of valves can be used to control flow and are especially affective in tight spots. Most times the handles are spring loaded and allow you to lock the valve into a certain position.


We like to give shout outs to any and all that help in the information department. So we would be remiss in not thanking Nibco for stopping in and giving us a little history and an engineering lesson regarding butterfly valves. We wanted to pass along that information to you so here goes. The butterfly valve was first used in the Russian oil fields. Some credit is given to Mr. Ivanovich Mendeleev. Mendeleev was a brilliant scientist and inventor who was also credited with putting together the first periodic table of elements, he also founded the first oil refinery in 1863.

The oil refinery needed something to control the flow of oil. Gate valves were bulky and difficult to move from line to line so the butterfly was born. The butterfly valve is generally 40% less money to buy and much easier to install. Just as a reference point, a 10″ Nibco gate valve weighs 490lbs, a 10″ Nibco butterfly valve weighs 70lbs. As you can see it’s a huge difference.

The materials used to manufacture the discs in a butterfly valve are as follows:

  • Cast Ductile Iron
  • Aluminum or Bronze
  • Stainless Steel
  • Buna or EPDM encapsulated disc.

There are few different types of methods to secure the shaft to the discs, here are the two most popular:

  • Stub Shaft – This has two stems. One going from the top down into the disc and one starting from the bottom and going up into the disc.
  • Bolt and Nut Drive – This stem is one piece and travels from the handle through the disc and is secured to the disc by a pin.

When choosing a butterfly valve determine it’s application before specifying the valve.

  • Will the valve be used bi-directionally? Will the flow of liquid be coming in both directions
  • If you are using a butterfly valve for a Dead End will it be used eventually? Is it a future?
  • What is the Dead End rating for the valve?

The inside surface area of a butterfly valve are usually lined with a material to extend the life of the valve. Not all liners are created the same, here are the different types of liners.

  • Cartridge Liner – This is a liner that fits inside the valve and is held in place by the stem. This is not the right valve to be used in a dead end application because of how the pressure is exerted inside the valve. The liquid tends to push on one side of the liner and with nothing but the shaft to secure it the liquid could get under the liner and foul the valve. This type of liner relies on the flanges outside the valve to keep it secure.
  • Boot Liner – This liner is more secure than the previous. It is secured by a ridge that is manufactured into the valve. The liner fits into the ridge.
  • Molded Liner – This is the best type of lined butterfly valve. It is made by injection molding and does not need flanges in place to secure the liner. This type of valve is effective in all circumstance where butterfly valves are specified.

Circuit Setter

This a very specialized valve used in the heating/cooling, HVAC and plumbing industry. We will give you a basic description of the valve and it’s functions but for further explanation please see our article on System Balancing.It is complex enough to warrant it’s own article and we would be doing the subject a disservice by not addressing it by itself.

A circuit setter is a balancing type valve used in an HVAC or plumbing system to regulate pressure in the whole system or within part of the system.

In a plumbing system it is used to regulated pressure between hot and cold water inside the potable water system. Many years ago a check valve and a ball valve where used, the check valve would shut down a hot or cold water supply if there was a sudden drop in pressure and the ball valve with a memory stop was used to regulate flow. This prevented cold or hot water bleed over if the pressure was increased or decreased in either supply piping.

Here are some things you should look for when choosing a circuit setter

  • What is the adjustment range of valve. Is the valve only able to adjust in quarter turn increments? If precision adjustment is needed look for a valve that has 360 degrees of adjustment.
  • What kind of test ports are on the valve. You should have a port for temperature and another for pressure.
  • Can you achieve a positive shut down for isolation purposes?

Gas Cock

A gas cock is a valve that is used to regulate low pressure natural or LP gas. The most common place to see this type of valve would be on the incoming gas supply for a kitchen appliance.

Gas Cock

The “old school” gas cock is a wedge type valve. Please see diagram below for a cross sectional view. The “wedge” when closed blocks the flow of gas, when the wedge is turned to the open position the wedge is hollow to allow the flow of gas. This is not a full port valve. New style gas valves are ball valves with small gas valve type handle.

Flush Valve

The diaphragm type flushometer was introduced by William Elvis Sloan in 1906. The diaphragm flush valve remains largely unchanged. The flush valve is comprised of two chambers, the upper and the lower. When the valve is not used both chambers are filled with water and equalized by the water supply pressure and it is kept equalized by the by-pass orifice. More about the by-pass orifice in a second. The handle is attached to a handle assembly, the flat end of the handle is butted up against the flat end of the operating stem.

Sloan Cut-Away

When the handle is depressed it pushes the operating stem which trips the stem of the diaphragm. This stem rocks the diaphragm out of the seat thereby releasing the water from the upper chamber. Because there is now less pressure in the upper chamber the diaphragm is pushed up from the water pressure in the lower chamber and flushing begins. The diaphragm slowly re-seats itself as water from the lower chamber enters through the by-pass orifice equalizing pressure between the two chambers.

Globe Valve

A globe valve is aptly named for it’s rather spherical body. A globe valve can be used to regulate flow in a plumbing line. Think of the valve body being bisected by baffles that are manufactured into the valve body and those baffles come together in the middle of the valve and that opening is closed by seating a disc or plug.

Globe Valve

The handle is attached to the stem which raises and lower the disc into place. Although this valve is affective as an isolation or regulating valve it does have it’s drawbacks. Because of the baffles it does not allow for full flow, there are too many right angles. Since the flow is restricted this type of valve may not meet engineering specifications where full flow is required.

Double Detector Check Valve

A double detector check assembly is one device that houses two check valve assemblies in the line of flow. The check valves are spring actuated and are designed to open with 1 pound of pressure. The double detector check assembly is installed with one (1) gate valve on the inlet of the valve and one (1) gate valve on the outlet side of the valve.These assemblies prevent back flow or back pressure in nonhazardous situations and are most used to protect the potable water system of a building from the water in a fire prevention system.

Double Detector Check Valve

A detector check is made with a by-pass assembly and meter to detect any unauthorized or illegal taps, test cocks are also present so that required yearly testing can take place. Each check valve can be isolated and tested independently to see if they are leaking and operating properly.

Reduce Pressure Zone Valve (RPZ)

An RPZ is very similar to the double detector check in that it houses two testable check valves. It has two gate valves one (1) on the inlet and one (1) on the outlet. Here is where things change, an RPZ is used in high hazard situations, where contamination of the water supply would pose a significant health hazard.

RPZ Reduced Pressure Zone Valve

An RPZ is designed with two check valves like a Double Detector Check Valve and a relief valve. The 1st check valve is calibrated to open at 5lbs of pressure the 2nd check valve is calibrated to open with 1lb of pressure and the relief valve which is the last line of defense and it is set to open with 2lbs of pressure and discharge to the atmosphere.

The relief valve is usually piped to a nearby floor drain so the room doesn’t flood if a large discharge occurs. This valve is built with redundancy in mind. If the pressure drops below 5lb of pressure the check closes on the outlet side if the pressure drops below a 1lb of pressure that check closes, if that check fails and the water by-passes the outlet check, it is released by the relief check.

Pressure Balance Valve

Scald protection and thermal shock are two terms that are used together and can overlap. Scalding can cause thermal shock which can then result in a fall or any number of injuries resulting from the shock of being scalded or blasted with ice cold water. How many of us have accidentally jumped in the shower just a few seconds before the hot water kicks in and nearly slipped and fallen?

RPZ Reduced Pressure Zone Valve

A pressure balance valve is a valve that protects against these types of issues buy regulating the amount of pressure within the valve. Pressure balance valves come in two varieties.

  • 1The first is a diaphragm type, this valve has the hot coming from one side and the cold from the other, the balancing disk is in the middle. The disk slides back and forth on a piston. Changes in pressure push against the disk and move the piston in the direction of the lower pressure and cuts off flow from the high pressure side.
  • 2The second in the spool type pressure balance valve, it has a spool inside the valve, the spool slides towards the supply with the lower pressure. This cuts off the volume of water entering the valve on the high pressure side and allows more water from the low pressure side. Output water temp cannot vary more than 3 degrees. ASSE Code 1016 defines scald protection valves. Both valves do not adjust for fluctuations in temperature.

Thermostatic Mixing Valve

This valve adjusts volume of water and protects the user by sensing water temperature. The most common type of thermostatic mixing valve has a paraffin wax element that expands and contracts based upon the supply temperature. If the wax gets hot the spool slides over to pinch off the hot side and vise versa. This type of valve is usually both temperature and pressure balanced.

Thermostatic Mixing Valve

There is another type of thermostatic mixing valve that uses a bi-metal strip. As the temperature changes so does the shape of the metal. As the metal changes shape it adjusts output temperature. As you can imagine a piece of metal that is constantly expanding and contracting can become brittle and eventually break. It’s one the reasons the wax element type valve has become the norm.

We hope you enjoyed the article. As with all of our articles feel free to add a comment or point out if you think something can be clarified.



    1. I’ve checked a few UK stores online and I’ll be honest I’m having a tough time finding a supplier. Give me a few. I’ve got a call into Sloan.


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