Plumbing System Controls & Valves
Guide to all types of controls used on plumbing systems

PLUMBING CONTROLS & VALVES - Description of common stop valves used on plumbing water supply piping
- Drain valves installed on water heaters, water tanks, heating boilers etc.
- 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.
Questions & Answers about plumbing system valve types & applications
References

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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 include stop valves, boiler drains, fuel valves, check valves, foot valves, etc. - just about every type of control valve used in residential buildings is defined and illustrated here. This list of the types of control valves found in residential and light commercial buildings includes links to detailed information about each valve type. .

Types of Plumbing Valves Used on Water Piping: Globe Valve, Gate Valve, Ball Valve Compared

Thanks to Carson Dunlop Associates, a Toronto Home Inspection Firm and Home Inspection Educator, for permission to use sketches shown in this article. Also see FAUCETS & CONTROLS, KITCHEN & BATH and FAUCETS, OUTDOOR HOSE BIBBS.

As Carson Dunlop Associates' illustrations below show, a broken water control valve stem can obstruct or block water flow through the valve. Globe valves (below left) 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.

Water control valve type (C) Carson Dunlop Assoc

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

On heating boilers and steam boilers the drain valve attached on or close to the boiler body is commonly called a boiler drain.
WATER HEATER DRAIN PROCEDURE - illustrates water heater drain valves
WATER TANK DRAIN VALVE - explains and helps locate drain valves used on water pressure tanks

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.

Fuel Valves: oil & gas piping in buildings

Fusible link oil line valve (C) Daniel Friedman

Gas Shutoff Valves
also see GAS PIPING, VALVES, CONTROLS and OIL & GAS PIPING
OIL LINE SAFETY VALVES - shown at left

Plumbing Fixture Valves

Typically at a sink or toilet the water supply is controlled by a local stop valve.

Appliance water control valves - installed at some dishwashers (usually hidden below the appliance) and at washing machines
FAUCETS & CONTROLS, KITCHEN & BATH - types, choices, installation recommendations and best practices guide
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

Plumbing & Heating Controls Valves, Service Valves, Safety Valves

AIRBOUND HEAT SYSTEM REPAIRS - discusses air bleeder valves
BACKFLOW PREVENTERS, HEAT used on hot water heating systems
CHECK VALVES, HEATING SYSTEM - used on hot water heating systems
Drain valves: also referred to as boiler drains, tank drains, are found on water pressure tanks, water heater tanks, heating boilers, steam boilers, range boilers, and other tanks and containers. Our Carson Dunlop Associates sketch (left) illustrates a gas fired water heater - the heater's drain valve, often made of plastic, is shown at the bottom right in this illustration.
Low Water Cutoff Valves, Boilers on hot water or hydronic heating systems
LOW WATER CUTOFF CONTROLS on steam heating systems
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. Also see MIX VALVE SCALD PROTECTION, Best Practices
OIL LINE SAFETY VALVES
RELIEF VALVE LEAKS
RELIEF VALVES - TP Valves on Boilers
RELIEF VALVES - STEAM TP VALVES
RELIEF VALVES - Water Heaters
RELIEF VALVES - Water Tanks
SPILL SWITCHES - Flue Gas Detection may act as either a control that turns off the gas burner or shut off the gas supply to the appliance
Water Feeder Valves, Hydronic Boiler
WATER FEEDER Valves, Steam heat systems
Zone Valves

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.

Other Plumbing System Control Valves

CHECK VALVES, WATER SUPPLY or backflow preventers are used on on water supply piping are used on well piping systems to prevent back-contamination of the public water supply. Note that in many jurisdictions use of a conventional check valve is not a suitable substitute for a backflow preventer. .
CHECK VALVES, WATER SUPPLY - on building drain and sewer piping and at sewage ejector pumps are used on building drain and sewer piping to prevent backflow or sewage into the building
CHECK VALVES, WATER SUPPLY - on water supply piping are used on well piping systems to prevent loss of pump prime.
FAUCETS & CONTROLS, KITCHEN & BATH - types & features of faucets used at sinks & tubs
FAUCETS, OUTDOOR HOSE BIBBS - oudoor faucets, hose bibbs, sill cocks, hose hookups, and freeze-proof faucets
FOOT VALVES - on the bottom end of well piping in the well, to avoid loss of prime
MAIN WATER SHUTOFF VALVE - controls water supply to the building whether delivered by municipal water main or by private pump and well system
WATER PRESSURE REDUCER / REGULATOR - a specialized water control valve that regulates water pressure within the building as municipal water supply pressure varies. Also see WATER PRESSURE REGULATOR ADJUSTMENT
Water SOFTENER ADJUSTMENT & CONTROLS include a bypass valve that takes the water softener out of operation
WATER TANK AIR VOLUME CONTROLS and WATER TANK AIR INLET VALVE control the volume of air required in the water pressure tank
Water Tank Relief Valve should be installed on all water pressure tanks

Frequently Asked Questions (FAQs) about valves found on building plumbing, heating, water supply, and other systems.

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.

Details about flushometer valves and their installation, troubleshooting, diagnosis and repair are now found at FLUSHOMETER VALVES for TOILETS URINALS.

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 & completyely restricts my hot water flow. - Randall Doran

Reply: thermosiphon prevention device?

Randall,

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

We discuss details about water heater controls at OIL FIRED WATER HEATERS.

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. 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:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
- Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
  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 Home Reference Book, a reference & inspection report product for building owners & inspectors.
  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.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
  Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
- 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.
- 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.
Thanks to reader - R.S. (anonymous by req.) for discussing hot water loss problems - August 2010
[1] Helvex
[2] Sloan Valve Company, 10500 Seymour Ave., Franklin Park IL 60131, Tel: 847-671-4300, website: sloanvalve.com
[3] 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
[4] 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

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

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.

Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.

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Drinking Water Testing Advice for home buyers home owners home inspectors
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Drinking Water Contaminant Levels - Maximum Allowed
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Sewage Levels in Septic Tanks - what are normal and abnormal sewage levels in septic tanks and what do they mean about tank condition, leaks, etc.
Sewer Line Replacement diagnosing a clogged drain leads to drain line replacement - step by step photo-illustrated guide to drain replacement
Water Pressure Loss - Diagnosis how to determine why water pressure has been lost or why there is no water at all in a building
Water testing for Pesticides: comprehensive and pesticides-example parameters
Water Testing: background comments on classes of water contaminants, & links to home buyer advice about water testing, drinking water, water supply
When and How to Shock or Chlorinate a Well - Procedure for Shocking a Well to (temporarily or maybe longer) "Correct" Bacterial Contamination
Water Requirements, Home & Outdoor Living
Typical Water Tests & Fees this water test fee schedule applies when testing is combined with other onsite building inspection services
Water pump and pressure tank repair diagnosis & cost an specific case offers an example of diagnosis of loss of water pressure, loss of water, and analyzes the actual repair cost
Water pressure tank failures & water pump short cycling diagnosis and repair
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