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How to measure water pressure at a building: this article describes how to measure water pressure and water flow in buildings in order to diagnose bad pressure or bad water flow. The process of water pressure problem diagnosis and the costs of the repair are explained.

Also see WATER PRESSURE REDUCER / REGULATOR for a discussion of how we reduce building water pressure to a safe level and how we assure uniform building water pressure and flow using a pressure reducing valve or pressure regulator. See WATER TANK PRESSURE GAUGE and WATER PRESSURE GAUGE ACCURACY for a discussion of built-in water pressure gauges. Readers whose building is served by a private pump and well system should see WATER PUMP PRESSURE CONTROL.

Distinguishing between static water pressure, dynamic water pressure, and water flow rate can help diagnose water problems in a building. Here we explain these concepts and we describe how to measure water pressure and flow at a property where either municipal water supply or a private well and pump water supply is in use.

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How to Measure Building Water Pressure: Definitions of Static Building Water Pressure & Dynamic Water Pressure

Definition of Static Water Pressure

Static water pressure is the pressure shown anywhere on the water supply piping system when no plumbing fixtures are running.

Typically on a municipal water supply the static water pressure in the building will be 30-60 psi, depending only on the setting of the water pressure regulator - the regulator determines static water pressure in the building.

On a private well and pump water supply system water pressure varies between 20-40 psi or 30-50 psi depending on the equipment installed and the pump pressure control switch settings. (See WATER PUMP PRESSURE CONTROL ADJUSTMENT).

Our photo (left) shows a simple and inexpensive home-made water pressure measuring gauge that we attached to the cold water faucet for a washing machine hookup. Building suppliers also sell water pressure gauges with the same fittings to attach the gauge to a hose or faucet hookup (see our page top photo).

To measure static water pressure, attach a pressure gauge anywhere in the building on water supply piping. Make sure that no plumbing fixtures are running, and if the building is served by a well and pump system, make sure that you have run water until the pump starts running, then turn water off. The pressure read on the gauge with all fixtures "off" is the maximum static water pressure at the building.

Definition of Dynamic Water Pressure

Dynamic water pressure is the pressure shown anywhere on the water supply piping system when one or more plumbing fixtures is drawing water. You can see that the more fixtures that are running, the lower the dynamic water pressure will be.

On a municipal water supply system the dynamic water pressure and flow seen in a building will drop to a number lower than the static water pressure but will normally remain steady when you turn on one or more plumbing fixtures.

On a pump and well water supply system the dynamic water pressure and flow seen in the building will drop to a lower number than the static water pressure, and will also vary as the pump cycles on and off.

Example of variation in building water pressure:

• Incoming building water pressure is 80 psi at the street-side of the pressure regulator.
• The pressure regulator is set to 60 psi and installed on 1/2" diameter building water supply piping
• The building has four apartments and in each apartment simultaneously people are running multiple plumbing fixtures, drawing water out of the system so fast that ...
• The dynamic building water pressure drops to 20 psi when all of these fixtures are operating. Even though the pressure regulator is set to 60 psi, when water flow in the building exceeds the capacity of the incoming water main to deliver water at that pressure, the in-building water pressure will drop to a lower number. A solution to this problem may be the installation of a WATER PRESSURE BOOSTER PUMP.

On a pump and well water supply system when multiple plumbing fixtures are operating, the dynamic water pressure will fall to a lower number and will hover there once the quantity of water being drawn causes the pump to turn on and stay on - that is, when you are running water fast enough that the pump cannot "get ahead" of the water draw out rate.

How to Measure Municipal Water Pressure

Static municipal water pressure may vary at different times of the day depending on what pressure is being delivered by the municipal supplier. In some communities municipal water pressure varies little while in others the variation can be significant.

To measure municipal water pressure in a building, use a water pressure test gauge like the home made water pressure test gauge shown above or the store-bought water pressure gauge shown at page top.

Install the water pressure gauge at a convenient outside hose bibb or to the drain connection on a water heater, or at a washing machine hot or cold water hose connection point.

If the building water pressure gauge reading is below 60 psi, leave the gauge in place for two days, checking it frequently for different pressure readings, because water pressure may vary by time of day or by the plumbing fixtures in use in the building.

An advantage of the store-bought Watts water pressure test gauge over the home-made version is that the special Watts test gauge includes a high-point red indicator needle that will record the highest water pressure sensed by the gauge during the test period, even if you did not happen to be looking at the gauge when that condition occurred.

Since your water pressure measurement itself could be inaccurate, see WATER PRESSURE GAUGE ACCURACY where we explain causes of false high water pressure readings and false low water pressure readings. For pressure gauge repair or replacement see WATER TANK PRESSURE GAUGE.

How to Interpret Your Municipal or City Water Pressure & Flow Measurements

If your dynamic water pressure is too low on a municipal water supply system you can boost building water pressure by installing a pressure booster pump and water tank. See WATER PRESSURE BOOSTER PUMP. Also see our discussion of parallel water pressure reducing valves found at WATER PRESSURE REDUCER / REGULATOR.

If your municipal or city water pressure is always too low, perhaps below 30 psi, see WATER PRESSURE LOSS DIAGNOSIS & REPAIR.

For more help figuring out why your municipal water pressure is too weak, see MUNICIPAL WATER PRESSURE DIAGNOSIS and then see MUNICIPAL WATER PRESSURE IMPROVEMENTS. Also see WATER PRESSURE VARIATION CAUSES.

Watch out: If the building water pressure gauge reading is ever found at 80 psi or higher, you will want to install a water pressure regulator at the point where water supply enters the building. Watts produces a Watts Governor 80™ used for this purpose, but other manufacturers also produce a wide variety of water pressure regulators.

If your building already has a water pressure gauge installed, it may be defective or it may be set too high. If your static water pressure is too high on a municipal supply, see  WATER PRESSURE REDUCER / REGULATOR. The articles listed just below discuss how water pressure reducers / pressure regulators work and how to adjust a water pressure regulator:

  WATER PRESSURE REDUCER / REGULATOR
    What's a Water Pressure Regulator?
    Direct-Acting Pressure Reducing Valves
    Regulate High Incoming Water Pressure
    Select Proper Pressure Reducing Valve
    Wire Draw Leaks at Pressure Reducers
    Parallel Pressure Reducing Valves
    Expansion tanks relieve high pressure
    WATER PRESSURE VARIATION CAUSES
    WATER PRESSURE REGULATOR ADJUSTMENT
    Water Pressure Regulator Test, Repair
  WATER PUMP PRESSURE CONTROL ADJUSTMENT

At HOT WATER PRESSURE EXPANSION RATE we discuss how we measure water pressure and how temperature changes affect water pressure in a closed water heater tank or heating boiler.

How to Measure Private Pump & Well Water Pressure

Static well water pressure depends on the setting of the pump controls. You can try reading the water pressure shown on the pressure gauge that is usually installed at the pressure tank or near the pump pressure control switch.

Watch out: dirt or debris in the small diameter pressure switch mounting pipe at your water pressure tank, or a failing pressure gauge itself can give inaccurate water pressure readings. Particularly if your water pressure gauge reading does not rise and fall smoothly as the water pump turns on and off, you may want to replace the gauge and/or make an independent water pressure reading using the water pressure test gauge we have described just above.

Since your water pressure measurement itself could be inaccurate, see WATER PRESSURE GAUGE ACCURACY where we explain causes of false high water pressure readings and false low water pressure readings. For pressure gauge repair or replacement see WATER TANK PRESSURE GAUGE.

How to Interpret Your Private Well Water Pressure & Flow Measurements

If your well water pressure is always too low, perhaps below 30 psi, see WATER PRESSURE LOSS DIAGNOSIS & REPAIR. Also see WATER PRESSURE VARIATION CAUSES.

If your dynamic well water pressure is too low on a private pump and well system you may be able to boost water pressure by adjusting the pump pressure control switch. See WATER PUMP PRESSURE CONTROL ADJUSTMENT. Also, because poor water flow rate from a private well system is often due to a limitation of the well's flow rate, see WATER PRESSURE LOSS DIAGNOSIS & REPAIR.

Watch out: If your well water pressure is too high, see WATER PUMP CONTROLS & SWITCHES and see WATER TANK SAFETY.

Diagnosis of private water well problems divides roughly into these areas

WATER PUMP CONTROLS & SWITCHES
WATER PUMP PROBLEM DIAGNOSTIC TABLE
WATER TANK REPAIRS

WELLS CISTERNS & SPRINGS

How to Measure Water Flow Rate in a Building - Bucket & Stopwatch

Our photo (left) shows water running into a five-gallon plastic bucket. If this is the only fixture running water in the building we can time the number of seconds or minutes needed to fill the bucket.

For example, if the time required to fill the five gallon bucket is one minute, then the water flow rate at this plumbing fixture is 5-gallons per minute or 5 gpm.

One can purchase "flow meters" that connect to various plumbing fixtures to pretend to make this measurement, but remember that we are measuring the flow rate at the particular fixture - to obtain a number that does not necessarily describe the water flow rate capability of the water supply system.

The measurement of water flow rate at a particular plumbing fixture does not accurately measure the true water flow rate of the plumbing system because:

• Different flow rates will be found at individual fixtures depending on the water flow restriction of the fixture itself, its' faucet strainer or even a disk that has been inserted into the faucet or shower head (for example) to deliberately restrict the water flow rate.
• Water piping supplying a particular fixture may restrict flow rate depending on the length and diameter of piping as well as possible hidden errors in the plumbing system such as a partial pipe blockage by solder at a copper joint, or blockage in the water supply piping if it is clogged by minerals or rust.
• Water flow on a well pump and tank system will vary during the measurement period depending on just when the water pressure drop turns the well pump on or off.

On a pump and well system when we turned on water at just the kitchen sink (Dynamic Water Pressure photo above) the flow rate dropped slowly until the pump turned on. Then the water pressure rose slowly until the pump turned off. Water pressure varied between 38 psi (pump off) and 25 psi (pump on).

When we turned on water at a bath tub faucet (photo just above) water pressure dropped to about 28 psi and stayed there as the well pump ran continuously, delivering water to the building at that rate. You can see our pressure gauge reading 28 psi.

Frequently Asked Questions (FAQs) about how to measure buiding water pressure

Question: Does closing a water supply pipe stop valve part way reduce water pressure in the building?

this may sound silly but by reducing the flow via the stop tap do you reduce the pressure - Allan

Reply: No. Here is the difference between water flow rate and water pressure

Does closing a stop valve reduce water pressure? Well yes if you mean flow rate and no if you mean static water pressure in the system.

No honest question is silly - thanks for asking.

Properly speaking, no, reducing the water flow rate does not reduce the STATIC pressure in the system in that the water pressure is determined by the water pump cut-off pressure setting on the pressure control switch if you have a private well, or by the street pressure and /or local water regulator pressure if you have a municipal water supply.

So if you are not running water - it's turned off - and you measure the water pressure using the methods we describe above, the water pressure will be the same regardless of whether or not a stop valve is partly closed.

But lots of people use the term "water pressure" to mean the DYNAMIC water pressure - how fast water comes out of the faucet. We call that the flow rate.

And yes, if you partly close a stop tap or valve, you will get slower water flow at any faucet or plumbing fixture that is downstream from that valve. That's because we're now supplying water through a smaller opening, so at the same starting pressure or static pressure, the volume of water that flows through that valve will be less per minute if the valve is partly closed than it would be if the valve were fully open.

Questions & Answers regarding this article

Questions & answers about how to accurately measure water pressure & water flow rate in buildings.

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Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

WATER PRESSURE & FLOW MEASUREMENT
  WATER PRESSURE VARIATION CAUSES
  WATER PRESSURE TOO HIGH: DANGERS
  Definition of Static Water Pressure
  Definition of Dynamic Water Pressure
  Measure Municipal Water Pressure
  Measure Pump & Well Water Pressure
  WATER FLOW RATE MEASUREMENT
  HOT WATER PRESSURE EXPANSION RATE

WATER PRESSURE GAUGES
WATER PRESSURE GAUGE ACCURACY

• Watts, 815 Chestnut Street, North Andover, MA, USA 01845-6098, web search 09/18/2010 Watts Regulator Corporation, 815 Chestnut Street, North Andover, MA, USA 01845-6098, provides pressure and temperature relief valves, water pressure test gauges, water pressure regulators, backflow preventers, check valves, and other plumbing and heating controls and supplies. Website: http://www.watts.com/
  • Watts Backflow preventers - 978-688-1811
  • Watts Control valves - 713-943-0688 for example Watts pressure reducing valves, original source: http://www.watts.com/pages/learnAbout/reducingValves.asp?catId=64
  • Watts Drainage products - 828-288-2179
  • Watts Potable water PEX plumbing - 978-688-1811
  • Watts Water safety controls - 978-688-1811
  • Watts Water quality & conditioning products - 352-465-2000

• Plumbing Diagnosis & Repair: Water supply, drainage, septic systems, water testing, water contamination, defective plumbing materials & products.
• 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
• Engineering toolbox properties of water - http://www.engineeringtoolbox.com/water-thermal-properties-d_162.html editor.engineeringtoolbox@gmail.com web search 09/16/2010
• SI Metric.co.uk provides tables and constants for the properties of water - web search 09/16/2010 original source: http://www.simetric.co.uk/si_water.htm
• Wikipedia on the Density of water at 1 atmosphere, web search 09/16/2010, original source: http://en.wikipedia.org/wiki/Density

Water Supply & Drain Piping, Wells, Pumps, Water Supply Equipment

• Access Water Energy, PO Box 2061, Moorabbin, VIC 3189, Australia, Tel: 1300 797 758, email: sales@accesswater.com.au Moorabbin Office: Kingston Trade Centre, 100 Cochranes Rd, Moorabbin, VIC 3189
  Australian supplier of: Greywater systems, Solar power to grid packages, Edwards solar systems, Vulcan compact solar systems, water & solar system pumps & controls, and a wide rage of above ground & under ground water storage tanks: concrete, steel, plastic, modular, and bladder storage tanks.
• Cheating on water tests: Testing Water for Real Estate Transactions - make sure your water test is valid
• Diagnosing Clogged Drains: Is it a blocked drain or the septic system? - A First Step for Homeowners
• Drinking Water Contaminant Levels - Maximum Allowed
• Drinking Water Supply, Contamination Levels, Water Testing Procedures
• Drinking Water Testing Advice for home buyers home owners home inspectors
• Interpreting Drinking Water Test Results and Correcting Unsatisfactory Water
• Lead Contamination in Drinking Water: Testing & Correction - Advice (This Article)
• Lead Testing & Correcting Contamination from Lead Water Supply Lines/Entry Mains - Lead Pipe Problems/Advice
• Life Expectancy of Water Pumps - Well Pumps: how long should a water pump last? What affects pump life?
• Life Expectancy of Wells & Water Tanks how long should a water well and its components last?
• Plumbing Diagnosis & Repair: Water supply, drainage, septic systems, water testing, water contamination, defective plumbing materials & products.
• Shock or Chlorinate a Well, How to - Procedure for Shocking a Well to (temporarily or maybe longer) "Correct" Bacterial Contamination
• Smart Tank, Installation Instructions, Flexcon Industries, 300 Pond St., Randolph MA 02368, www.flexconind.com, Tel: 800-527-0030 - web search 07/24/2010, original source: http://www.flexconind.com/pdf/st_install.pdf
• Typical Shallow Well One Line Jet Pump Installation, Grove Electric, G&G Electric & Plumbing, 1900 NE 78th St., Suite 101, Vancouver WA 98665 www.grovelectric.com - web search -7/15/2010 original source: http://www.groverelectric.com/howto/38_Typical%20Jet%20Pump%20Installation.pdf
• Typical Deep Well Two Line Jet Pump Installation, Grove Electric, G&G Electric & Plumbing, 1900 NE 78th St., Suite 101, Vancouver WA 98665 www.grovelectric.com - web search -7/15/2010 original source: http://www.groverelectric.com/howto/38_Typical%20Jet%20Pump%20Installation.pdf
• Water Fact Sheet #3, Using Low-Yielding Wells, Penn State College of Agricultural Sciences, Cooperative Extension, School of Forest Resources, web search 07/24/2010, original source: http://pubs.cas.psu.edu/FreePubs/pdfs/XH0002.pdf
• Water pressure tanks - how to diagnose the need for air, how to add air, stop water pump short cycling to avoid damage - water storage water pressure tank safety.
• 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
• Water Supply & Drain Piping, water and drain pipe types, inspection, diagnosis, repairs, problem materials, clogging, etc.
• Water Tests & Fees this water test fee schedule applies when testing is combined with other onsite building inspection services
• Water Testing: background comments on classes of water contaminants, & links to home buyer advice about water testing, drinking water, water supply
• Water Requirements, Home & Outdoor Living

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, 2010, $69.00 U.S., is available from Carson Dunlop, and from the InspectAPedia bookstore. The 2010 edition of the Home Reference Book 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. InspectAPedia.com ® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.

• Crystal Clear Supply provides portable ceramic water filter purifiers and portable reverse osmosis water treatment equipment - see http://www.crystalclearsupply.com/category_s/7.htm
• Handbook of Disinfectants and Antiseptics, Joseph M. Ascenzi (Editor), CRC, 1995, ISBN-10: 0824795245 ISBN-13: 978-0824795245 "The evaluation of chemical germicides predates the golden age of microbiology..." -
  This well-focused, up-to-date reference details the current medical uses of antiseptics and disinfectants -- particularly in the control of hospital-acquired infections -- presenting methods for evaluating products to obtain regulatory approval and examining chemical, physical, and microbiological properties as well as the toxicology of the most widely used commercial chemicals.
• Potable Aqua® emergency drinking water germicidal tablets are produced by the Wisconsin Pharmacal Co., Jackson WI 53037. 800-558-6614 pharmacalway.com
• Principles and Practice of Disinfection, Preservation and Sterilization (Hardcover)
  by A. D. Russell (Editor), W. B. Hugo (Editor), G. A. J. Ayliffe (Editor), Blackwell Science, 2004. ISBN-10: 1405101997, ISBN-13: 978-1405101998.
  "This superb book is the best of its kind available and one that will undoubtedly be useful, if not essential, to workers in a variety of industries. Thirty-one distinguished specialists deal comprehensively with the subject matter indicated by the title ... The book is produced with care, is very readable with useful selected references at the end of each chapter and an excellent index. It is an essential source book for everyone interested in this field. For pharmacy undergraduates, it will complement the excellent text on pharmaceutical microbiology by two of the present editors."
  The Pharmaceutical Journal: "This is an excellent book. It deals comprehensively and authoritatively with its subject with contributions from 31 distinguished specialists. There is a great deal to interest all those involved in hospital infection ... This book is exceptionally well laid out. There are well chosen references for each chapter and an excellent index. It is highly recommended." The Journal of Hospital Infection.: "The editors and authors must be congratulated for this excellent treatise on nonantibiotic antimicrobial measures in hospitals and industry ... The publication is highly recommended to hospital and research personnel, especially to clinical microbiologists, infection-control and environmental-safety specialists, pharmacists, and dieticians."
  New England Journal of Medicine: City Hospital, Birmingham, UK. Covers the many methods of the elimination or prevention of microbial growth. Provides an historical overview, descriptions of the types of antimicrobial agents, factors affecting efficacy, evaluation methods, and types of resistance. Features sterilization methods, and more. Previous edition: c1999. DNLM: Sterilization--methods.
• U.S. Army Field Manual 21-10, Field Hygiene and Sanitation, 1988, web search 07/02/2010, original source: http://www.enlisted.info/field-manuals/fm-21-10-field-hygiene-and-sanitation.shtml
  The purpose of this manual is to assist individual soldiers, unit commanders, leaders and field sanitation teams in preventing disease and environmental injuries. The manual provides information on preventive medicine measures (PMM) to the individual soldier as well as essential information for the unit commander, unit leaders, and the unit field sanitation team on applying unit level PMM.
• When Technology Fails, Matthew Stein, Chelsea Green Publisher, 2008,493 pages. ISBN-10: 1933392452 ISBN-13: 978-1933392455, "... how to find and sterilize water in the face of utility failure, as well as practical information for dealing with water-quality issues even when the public tap water is still flowing". Mr. Stein's website is www.whentechfails.com/
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