InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
Plumbing valves guide:
This article describes and illustrate the different types of valves found on water supply and drainage systems as well as plumbing fixture valves and on other plumbing and heating devices & fixtures.
We discuss the definitions of globe valves, gate valves, and ball valves, the properties of drain valves installed on water heaters, water tanks, heating boilers etc. . We describe stop valves, boiler drains, fuel valves, check valves, foot valves, etc.
This list of the types of control valves found in residential and light commercial buildings includes links to more-detailed information about each valve type.
We explain stop valves installed at plumbing fixtures. Gas and oil piping fuel line stop and control valves & check valves. Links to details about all types of plumbing system valves on supply piping, drain piping, & plumbing fixtures or appliances: check valves, flushometer valves, etc.
Types of Plumbing Valves Used on Water Piping: Globe Valve, Gate Valve, Ball Valve Compared
Above we illustrate the three most-common types of valves used in plumbing, a globe valve, a gate valve, and a ball valve, each shown in a partly-open position.
The yellow handle on the ball valve tells us that this valve is approved for use on gas piping installations. We're showing these valves in a partly-open position to make the valve mechanism more-obvious. But only the globe type stop valve is intended to be left at settings between fully open and fully shut.
Here we use Carson Dunlop Associates' sketches and our own photographs to define and explain the differences in design and intended of a globe valve, a gate valve, and a ball valve in plumbing applications.
Definition: Globe valves provide easier regulation of water flow but use a washer and valve seat that must be maintained and that can fail from corrosion or pitting.
Because of the complex valve passage through which water passes in a globe valve there is some water pressure (or flow rate) drop across the valve when it is open.
[Click to enlarge any image]
Globe valves (sketch above) tend to most restrict water flow compared with the gate valve (center) and ball valve (right). But a broken stem on a gate valve can also leave the valve stuck partly or even fully closed (or open), regardless of how you may be able to turn the valve handle.
Globe valves are often used as water shutoff valves on heating boilers, at outdoor hose bibbs or sillcocks, at water pressure tanks, clothes washer connections, and water heaters (calorifiers, cylinders, geysers).
Globe type valves are also used in a smaller form as fixture shutoff valves at sinks and toilets. Globe valves at fixtures are usually referred-to as stop valves.
Our photo above shows a pair of round-handled valves in a washing machine hookup provided by Oatey™. From the small body size of the valve I think these are probably globe valves.
Below is a globe valve used as a sill-cock or outdoor "hose bibb" for connecting a garden hose.
However you may find any of the three water control valves described here installed at a variety of fixtures.
Gate Valves for Water On/Off Control
Definition: Gate valves (sketch just above) are intended to be used in the fully-open or fully-closed position, that is, they are not good for regulating water flow through the valve.
The metal-to-metal seal of a gate valve is also subject to failure from corrosion, and on occasion we have found gate valves with a broken stem that left the valve stuck open or closed.
The user turns the handle and thinks he is changing the valve position but with a broken valve stem the gate does not move.
Ball Valves Used for Water Flow & On/Off Control
Definition of a Ball Valve
Ball valves (photo & sketch above) are also a type of gate valve but these controls use a spherical ball type gate with a hole bored through the ball. Turning the handle rotates the ball gate to open or close the valve.
Ball valves, like traditional gate valves, are intended to be left fully open (water on) or fully-closed (water off). Ball valves are also used on gas piping systems.
Watch out: Of the three plumbing valve types described here, only ball-valves are provided in models rated for use on gas piping. Ball valves intended for use on LPG or NPG gas piping will have a yellow handle and will bear a tag giving the valve's listing approval.
The white arrow in our photograph above shows a ball valve serving as the main water shutoff control on a water supply system.
You can usually spot a ball valve by its distinctive lever-type handle. When the ball-valve lever-type handle is set parallel to the water pipe the valve is in the open position - as in our photo above.
Gate valves of the traditional gate valve design and the ball valve design both permit water flow through the valve without pressure drop.
If you can see into the opening of a water control valve you can usually determine what type of valve it is. Above we see into the openings of a washing machine hook-up provided by Oatey™. You can see the shiny stainless steel sphere marking these as ball valves.
These special ball valves can be moved from fully-open to fully-closed in just 1/4 turn, especially useful where space is limited..
You may also have noticed the red and blue lever type handles that are characteristic of ball valves. With the washing machine hookup ball valve handle turned across the valve outlet the valve is in the closed position.
L-Port & T-Valves: Design, Usage, Features
What is a T-valve and what is an L-valve and how are they used?
Above, a T-valve that is used to switch flow between two different output destinations. [Click to enlarge any image]
Typical T-valves such as the Mondeo T-valve shown above, are ball-valves used to divert flow from a primary input source to one of two different destinations. The ball of the valve is drilled straight through and then an intersecting drill opening is made at a 90 degree angle to the first passage.
Ball valves are intended to be used in the fully-open or fully closed position. For a T-valve that means you'd send all of its output to one of two possible destinations. These valves are not usually intended to be used to send output to two destinations simultaneously.
With a L-port the ball is drilled from two different sides (90 degrees) and the drilling
resembles the shape of an L. The T-port valve is basically the L-port valve, but the ball is
drilled all the way through in one direction. So the drilling of the ball resembles the
shape of the letter T.
With a L-port, the middle port is the common port, and with a T-port, one of the side
ports is the common port. But this assumes you want to use a T-port ball to divert as you
would an L-port ball valve.
Definition & Common Applications for a L-port ball valve:
Divert a flow from one source tank to another source tank,
Divert a flow from one source, like switching between pump #1 and pump #2,
Diverting from free cooling to using a chiller due to seasonal demand
Diverting a flow to one storage tank to another storage tank
Definition & Common Applications for a T-port ball valve:
The applications are basically the same, but you can flow straight thru the valve in
position #1 and have less pressure loss and then divert in another direction in
position #2 when you want to choose between using one paint sprayer or both paint sprayers
at the same time (all three ports connected)
Piping arrangement suggests that the end port should be the common port
Replacement for lubricated T-port plug valve in tank farms
Boysen, Herman, Kv: What, WHy, How, Whence?, [PDF] Danfoss, (2011) retrieved 2017/12/12 original source: http://heating.danfoss.com/PCMPDF/VFHBG202_kv.pdf for an explanation of the use of Kv l when calculating relative pressure drops among different valves used in piping systems.
Also see SHUTOFF VALVE LOCATION, USE for a discussion of how to find, use, & repair building water supply shutoff valves and stop valves.
Drain Valves: boilers, water heaters, water pressure tanks
Boiler drain valve: (photos above) On heating boilers and steam boilers the drain valve attached on or close to the boiler body is commonly called a boiler drain. Our photos above illustrate globe valves used as the drain control on heating boilers. The most-common boiler drain valve uses a globe valve internal design.
Other drains on hydronic heating system may be present such as a drain on the heating system's expansion tank.
Water heater drain valve: (photo above) Water heater or water cylinder tank drain valves are usually a globe valve design just as the drains on heating boilers. But water heater drain valves are often made of plastic.
Watch out: fooling with a plastic-stemmed water heater drain valve can surprise you when the heat-aged valve stem breaks and water spurts into the building through the valve head. Do not force a stuck water heater drain valve.
Watch out: Often an unused or rarely-used plumbing valve may be stuck, may have lost an internal washer, and may otherwise fail to close properly if you touch it.
We advise against attempting to open or adjust heating equipment drain valves unless you are prepared to shut down the system and install a replacement valve in the event of a leaky valve that can't be shut off.
FLUSHOMETER VALVES for TOILETS URINALS - with adequate water pressure, flow, and volume and proper installation, the flushometer valve eliminates the requirement for a water reservoir tank at toilets and supports urinals in restrooms
Thanks to Carson Dunlop Associates, a Toronto Home Inspection Firm and Home Inspection Educator, for permission to use sketches shown in this article
Electric Solenoid Operated Gas, Oil, Water Valves used in Buildings
Here we describe electrically operated plumbing valves used for water control of equipment or piping in buildings.
Reader Question: where can I buy a solenoid-operated water shut-off valve?
15 January 2015 Martin said:
... Any ideas where I can purchase solenoid-operated water shut-off valves?
Martin a number of companies provide electrically-operated solenoid-type shutoff valves including valves that can close off a water supply line. The operating pressure range and piping diameters among the various products vary so you’ll want to contact the company’s technical or sales people to discuss your specific needs.
Prices for electric solenoid valves range from under $50. U.S.D. to over $500. U.S.D. depending on the application.
Saddle valves, also referred to as piercing valves or puncture valves, have been used to add low-flow water connections to refrigerator ice makers, humidifiers, and other appliances.
The saddle valve shown above, adapted from a Wikipedia illustration, has a plastic tube attached, perhaps feeding an ice maker. - Retrieved 2018/01/11 original source https://en.wikipedia.org/wiki/Saddle_valve#/media/File:Saddle_valve.jpg
The valve body clamps onto an existing copper water pipe.
When the valve's T-handle is turned down a pointed end on the valve gate pierces the copper piping.
When the valve is backed open water can flow into tubing attached to the saddle valve outlet.
In our OPINION these valves, though convenient, do not work reliably if the valve must be frequently opened or closed.
Watch out: saddle valves are prohibited by some plumbing codes in some jurisdictions such as the U.S. Florida Plumbing Code, the Virginia Plumbing Code, and the 2009 IPC. Other plumbing codes do not explicitly approve the use of saddle valves but do not mention them by name.
2009 International Plumbing Code & Virginia Plumbing Code
605.9 Prohibited joints and connections. The following
types ofjoints and connections shall be prohibited:
1. Cement or concrete joints.
2. Joints made with fittings not approved for the specific
3. Solvent-cementjoints between different types of plastic
4. Saddle-type fittings.
707.1 Prohibited joints. The following types of joints and
connections shall be prohibited:
1. Cement or concrete joints.
2. Mastic or hot-pour bituminousjoints.
3. Joints made with fittings not approved for the specific
4. Joints between different diameter pipes made with
elastomeric rolling O-rings.
5. Solvent-cementjoints between different types of plastic
Reader Question: Installing a pressurized system & Flushometer Valve Toilets & Urinals on a Well & Pump Water Supply System
I have a well system at a marina and would like to install commercial flushometer toilets and urinals. It is old and is currently served by a standard residential system.
I have space above the rest rooms and would like to install a stand alone pressurized system that is fed by the existing residential system, but would provide the gpm and pressure to function the commercial units. Likely to be a total of 3 toilets and two urinals.
Any ideas or plans available? Thanks, Bill
Reply: Be sure that your well water supply system, pressure tank, pressure, and water supply piping diameter & flow rate can support flushometer valves; consider waterless urinal fixtures.
Bill, there is no technical reason why one could not install flushometer type toilets and urinals at a property served by a standard pump and well system, but the cost and trouble may be more than first meets the eye.
Where we find flushometer type toilets and urinals installed it's usually at a building served by municipal water supply and employing larger diameter water supply piping than the 1/2" pipe usually found at residential type properties.
That's because flushometer fixtures, relying on both water pressure and total gpm flow rate to work properly, need a higher pressure and total flow rate than most residential systems deliver
You can achieve the necessary pressure and water quantity for the fixtures by adding a water tank and pump at a suitable location, but you might need also to install larger diameter water supply piping to each fixture.
Reader Question: what's the purpose of the inline float valve at the top of an electric water heater? Can I remove it?
What is purpose of & is it necessary ? In- line ball- cock valve in water entry line going into top of electric water heater. Would it be ok to eliminate line containing floating ball ? It sticks & completely restricts my hot water flow. - Randall Doran
Reply: thermosiphon prevention device?
I'm guessing from your description that you are describing an anti-siphon valve at the top of your water heater. The valve is intended to prevent hot water from circulating up into the building water supply piping by "gravity" (warm or hot water, being less dense than cold water, will naturally rise up out of a hot water tank into cooler water in building piping).
If that's what you've got you could remove the valve but the result might be wasted energy - sending hot water out into building piping (where it will cool off) when no hot water is being drawn at a plumbing fixture.
In general you could eliminate a control valve feeding water into your water heater, but it will make it impossible to turn off "hot" water in the building when service or repair to the heater is needed - you'll instead have to turn off water to the whole building.
Watch out: An improperly installed shutoff valve on a water heater can be very dangerous, risking an explosion. Usually the "hot water tank shutoff valve" is installed only on the cold water pipe coming into the water tank. There should be no shutoff valve installed on the hot water line leaving the water tank.
See WATER HEATER SAFETY
MIXING / ANTI-SCALD VALVES - found on tankless coils used for making domestic hot water and at other hot water supply systems that produce very hot water; also found installed directly at some plumbing fixtures such as sinks, tubs, and showers.
Watch out: do not touch, open, or otherwise manipulate relief valves on heating equipment unless you are prepared, should the valve leak, to shut down the heater and replace the leaky valve immediately.
Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
The questions and replies about types of valves used in plumbing and other building mechanical systems were posted originally at this aticle: PLUMBING CONTROLS & VALVES .
Ask a Question or Search InspectApedia
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Thanks to reader - R.S. (anonymous by req.) for discussing hot water loss problems - August 2010
 Sloan Valve Company, 10500 Seymour Ave., Franklin Park IL 60131, Tel: 847-671-4300, website: sloanvalve.com
 Sloane-Regal Installation Instructions for Standard Exposed Closet and Urinal Flushometers, Regal I.I. Code 816312, Models 110/111 through Model 117. 120-122, and 180, 186, 1997, Sloan Valve Company, 10500 Seymour Ave., Franklin Park IL 60131, Tel: 847-671-4300, website: sloanvalve.com
 Sloane Installation Instructions for Exposed Regal® XL Water Closet and Urinal Flushometers, Code 0816312 (newer version of above document), Rev. 1 05/10, Sloan Valve Company, 10500 Seymour Ave., Franklin Park IL 60131, Tel: 800-982-5839, or 888-SLOAN-14 / 888-756-2614, website: sloanevalve.com
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: firstname.lastname@example.org. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones