Accuracy of Air & Water Pressure Gauges - how to get an accurate pressure reading InspectAPedia® -
How to select and use an air or water pressure gauge to obtain accurate pressure readings
How to check and adjust air pressure in an internal bladder well water tank
Causes of false high water pressure readings at a water tank gauge
Causes of false low water pressure readings at a water tank gauge
Relation between gauge water pressure and water pump cut-in or cut-out pressures
Questions & answers about water pressure gauges
This article describes how to select and use an air or water pressure gauge to obtain accurate pressure readings, and what causes inaccurate water tank pressure gauge readings. We explain how water gauges may become stuck or inaccurate and we suggest ways to test and repair misbehaving water pressure gauges.
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Readers should also see WATER TANK PRESSURE GAUGE where we describe water pressure gauges and their repair or replacement. Readers concerned with water pumps, tanks, and wells themselves should see WATER PUMPS, TANKS, TESTS, WELLS, REPAIRS.
The page top photo shows the author testing the air pressure in a Well-X-Trol bladder type well tank. To buy or make your own portable water pressure measurement gauge, see WATER PRESSURE & FLOW MEASUREMENT.
How to Read Water Tank Pressure or any Pressure Gauge Accurately
Stuck Water Pressure Gauges
For digital pressure gauges such as the one we demonstrate in photos on this page, gauge accuracy and our ability to read the pressure gauge accurately may not be a concern. Our photo at above left shows the water pressure gauge at the bottom of a water tank.
The left hand pressure gauge is "stuck" at a high pressure, probably from rust or debris entering the gauge bottom port. Our photo at above right shows an identical gauge (same manufacturer) installed on the same water system, but located on the water pump itself. It is reading accurately.
But for dial-type pressure gauges or for "stick type" tire gauges (photos above left and right) use an indexed stick that protrudes from the gauge bottom. The accuracy with which a gauge reports and you can read pressure varies. We don't trust stick-type pressure gauges for accuracy. Dirt on the sliding indicator gauge, age, loss of lubricant, quality of manufacture (on some units, not all), and errors in reading the gauge all lead to errors, sometimes substantial errors.
Choose a Pressure Gauge With the Proper Operating Pressure Range
For the most accurate pressure readings when using any pressure gauge for any purpose, select a pressure gauge whose operating range is only slightly larger than the actual operating pressure range of the equipment you are testing.
For example, if you are testing pressures on a water system that operates between 0 psig and 50 psig, a pressure gauge that handles pressures from 0 to 60 psi (photo at left) will be more accurate (and easier to read) than a pressure gauge whose display handles pressures from 0 psi to 500 psi.
The gauge we show here will keep the pressure reading on its dial until you press the button on the side of the gauge (lower right in photo) - making it a bit easier to obtain a pressure reading in tight quarters.
Be sure to read the correct scale on your pressure gauge if it has more than one set of markings.
In our photo the outer white scale from 0-60 is in psi while the inner scale in yellow is marked in kiloPascals.
To convert kPa or Kilopascals to pounds per square inch or PSI use this simple formula:
Kilopascals x 0.1450 = PSI or pounds/square inch
Diagnose Jumpy or Erratic Water Pressure Gauge Readings
Question:
I have an additional observation with regards to my well water system. I noticed last weekend when I was filling an above ground pool that the gauge at the well water pump was going as high as 20psi and then bouncing down to 0psi and then back to 20psi. The gauge was very jumpy. Is it possible that the well pump, although the well pump sounds like it is pumping properly, could possibly be flawed?
The pressure tank was recently replaced due to a ruptured bladder. I have no Idea how long it was working that way for I purchased the house in October of 2009. I still believe that I have a pressure problem. I filled a pool so I do not think I have a water quantity problem. Could you please advice as to your thoughts on this issue? - Thanks, Tony
Reply:
Water pressure gauges can be jumpy due to a partly clogged gauge or gauge piping, defective gauge. A pump cycling on and off would not explain pressure reading varying between 0 and 20 unless your pressure gauge was not turning on the pump until pressure reached 0 - that'd be unusual. If you check water pressure and flow independently from the jumpy gauge you'll know what's going on and can then home in on the gauge if that's the problem. See the suggestions below for checking on the actual water pressure in a plumbing system and on comparing the system pressure and pump behavior to the gauge behavior.
Other causes of odd pressure gauge behavior include an intermittent blockage at a water pressure tank such as a sticking water or air bladder.
But a problem in the well, pump, tank, piping that is causing a pressure variation or fluctuation would be expected to also affect the pump pressure control switch and turn the pump on and off accordingly. So it's reasonable, from your description to check on the system pressure independently of the jumpy water pressure gauge.
Ways to Check Water Pressure, Pump Pressure Controls, Water Pump Operation Against Gauge Pressure
Use an independent air pressure gauge or water pressure gauge and measure water pressure at
The air valve or schrader valve on the pressure tank when the pump is at the cut-in point and cut-out point
A water pressure gauge mounted at a convenient hose bib or washing machine water hose hookup
Try replacing the questionable water pressure gauge with a new one. Be sure that the mounting pipe or orifice where the gauge is installed is not blocked with sediment or debris.
Check Water Tank Pressure Using an Independent Pressure Gauge
Our photos just below show the author using a digital tire pressure gauge to measure the air pressure in a bladder-type water pressure tank or well tank.
Check the air pressure in the water tank by using an accurate air pressure gauge (such as a dial type or digital tire pressure gauge) to measure the air pressure at the schrader valve on the water tank. The tank pressure should be within 10% of the original factory water tank pressure setting. Our photo (above left) shows the water tank air inlet valve on the top of our Well-X-Trol well tank. We removed the cap and label for the photo.
Our photos, below, show these same pressure gauges in use to measure air pressure in an automobile tire - a Mini Cooper run-flat tire that needs to be kept accurately at the proper air pressure. Be sure to press the gauge orifice down firmly and straight onto the air valve. Regardless of whether you are checking pressure in a vehicle tire or a home water system well tank, holding the gauge askew will cause air to be lost out of the pressurized container.
Causes of False Water Tank Pressure Gauge Readings - too high or too low
While normally water pressure gauges do a great job and are reasonably accurate, on a water tank a water pressure gauge can give very inaccurate pressure readings, especially if it's pressure intake port, a small diameter hole, or the small pipe on which it's mounted are debris clogged. If your water supply contains sediment or debris, or if the water is high in iron or mineral content, this blockage becomes more likely.
False High Water Pressure Indications
Water under pressure has entered the gauge at the high-end of the pump on cycle, but its exit is blocked or slowed by blocking debris at the gauge. So when actual water system pressure falls (water is drawn out of the system, pressure drops typically 20 psi before the pressure switch turns the pump back on), the gauge continues to read higher than actual pressure.
False Low Water Pressure Indications
The system water pressure has fallen, perhaps to just below the pump cut-in pressure, and stays there long enough for the pressure gauge to slowly bleed its own higher pressure water out through a partly blocked opening. The indicated pressure on the gauge falls to some low level, in some cases even near zero. Additional water is drawn from the system, the pressure drops just enough more that the pressure control switch turns on the pump and system water pressure rises up to the cut-off or cut-out water pressure. But the gauge continues to read a false "low" because incoming water to its sensor port is blocked by debris.
Note that these debris blockage conditions that cause false high or low water pressure indications on a water pressure gauge are the same conditions that can occur at a water pump pressure switch, causing it to misbehave as well.
A water pressure gauge can also indicate incorrect pressure simply because the gauge is inaccurate (this is not precisely calibrated lab-grade equipment) or because the gauge has become damaged.
Remedy - How to Correct A Water Pressure Gauge that Reads too High or Too Low
The well pump is turned off, pressure is drained from the system (you do not have to let all of
the water out of the tank, just be prepared for a little spillage). Then the new water pressure gauge is prepared
for installation (make sure the gauge bottom threads match those of the old unit being replaced as
diameters vary from 1/4" to 1/2"). See WATER TANK PRESSURE GAUGE for details of how to repair or replace a water tank pressure gauge.
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Thanks to Jeremy Houser who suggested that we needed to clarify the difference between bladder type and non-bladder type water tanks when discussing air charging and diagnosis of water tank repairs.
Amtrol Extrol™ pressure control tanks, which they call well tanks, are described at the company's website at www.amtrol.com/extrol.htm and installation and operating instructions for these well tanks can be found at www.amtrol.com/pdf/9015A290revcWXT.pdf
Well-X-Trol: Amtrol Extrol™ pressure control tanks used on hydronic heating and other systems such as models 35LBC, 50 LBC, 85 LBC, and 100LBC to 600 LBC also use a bottom bladder containing air - see amtrol.com/pdf/LBCSeriesEXTROL9017-095.pdf for details.
Thanks to readers Nancy and Eric for questioning water pump gauge inaccuracies 11/2/2009
Thank to Tony for discussing jumpy erratic water pressure gauge behavior - August 2010
Wessels Company bladder replacement store was found at westank.com/bladder-tank-store.php on 5/22/2009. Wes sell refers to "shock and surge tanks" as ASME replaceable bladder type and pre-charged hydropneumatic tanks used for commercial, industrial, and well water systems.
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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
Smart Tank, Installation Instructions [ copy on file as /water/Smart_Tank_Flexcon.pdf ] - , 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 [ copy on file as /water/Jet_Pump_Grove_Elect_Jet_Pumps_1.pdf ] - , 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 [ copy on file as /water/Jet_Pump_Grove_Elect.pdf ] - , 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 [ copy on file as /water/Low_Yield_Wells_Penn_State.pdf ] - , 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.
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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)
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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.
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