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WATER PUMPS, TANKS, TESTS, WELLS, REPAIRS
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WATER FILTERS, HOME USE
WATER HAMMER NOISE DIAGNOSE & CURE
WATER ODORS, CAUSE CURE
WATER PUMP REPAIR GUIDE
WATER PRESSURE LOSS DIAGNOSIS & REPAIR
WATER PUMP SHORT CYCLING
WATER SOFTENERS & CONDITIONERS
WATER TANK REPAIR PROCEDURES
WATER TANK: USES, TROUBLESHOOTING
WATER TESTS, CONTAMINANTS, TREATMENT
WATER TREATMENT EQUIPMENT CHOICES
WELLS CISTERNS & SPRINGS
WELL CHLORINATION & DISINFECTION
WELL FLOW RATE
WELL WATER PRESSURE DIAGNOSIS
WELL YIELD IMPROVEMENT
WINTERIZE A BUILDING
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.
Green links show where you are. © Copyright 2015 InspectApedia.com, All Rights Reserved.
The page top photo shows the author testing the air pressure in a Well-X-Trol bladder type well tank.
[Click to enlarge any image]
At above left we show a typical residential pressure gauge at typical well-system shut-off pressure of 40 psi. At right we show a pressure gauge reading 84 psi - something is probably wrong with this system. If pressure is really this high (that is if the gauge is not defective) we're risking plumbing leaks or even a dangerous burst water tank.
Stuck Water Pressure Gauges
For digital pressure gauges such as the one we demonstrate in photos on This article , 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
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
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
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").
Continue reading at WATER PRESSURE GAUGE INSTALLATION
or see WATER TANK PRESSURE GAUGE for details of how to repair or replace a water tank pressure gauge.
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
Question: pressure gauge reads over 100 psi
(June 12, 2011) Cecile said:
What happen when the meter passes the 100 mark. Is it still 100 or 100+
Pressure gauge readings at or over 100 psi?
- no longer accurate
- likely to be damaged
Watch out: this condition is possibly dangerous as high pressure can blow out gauge components, burst piping, flood a building, or even blow up a tank, injuring someone
Question: pressure gauge "clicks" rapidly back and forth
(July 19, 2011) David said:
our pressure gauge is clicking back and forth rapidly...what does this mean?
I think you mean pressure control switch, right? A pressure gauge is just a dial that gives a guess at water pressure. If your gauge is varying or waving back and forth rapidly - really the gauge - then the pump must be also turning on and off rapidly - under the article links at page left titled
Question: water presssure gauge reads below zero
(Aug 14, 2011) Ron said:
My gauge reads below zero now and the pump is short cycling every few seconds. It use to read 40PSI then drop down to 20PSI and thats when the pump would kick in. Is it short cycling because of the gauge? When I check the pressure at the tank valve it read 38PSI.
Ron with a gauge showing no pressure and the pump short cycling you might have a blocked water inlet from the pump into the water pressure tank - such as a collapsed tank bladder.
The gauge itself won't cause short cycling - it's just an indicator, not a control.
If the gauge inlet port is clogged, remember that it's not accurately responding to system pressure.
But if the pump is short cycling you will want to look at steps to diagnose and fix the problem - see articles
at page left titled
Question: water pressure gauge won't go over 38 psi
(Oct 24, 2012) julliet said:
I replaced new 30/50 pressure switch. After turned on pump power, the pressure gauge went from 0 to 38 and won't go any higher. The pressure switch didn't open.
If your system pressure never goes above 38 psi and the switch is set to a 50 psi cutoff, perhaps
the gauge is inaccurate (I'd suspect this if the pump shuts off under switch control)
the pump is unable to reach the cut-off pressure because
-- the well has low water supply or low water flow
- something else we've not thought-of
Question: water pressure gauge accuracy when water-logged
(Sept 1, 2014) RajaRamanan said:
your product Accuracy of Air & Water Pressure Gauges - how to get an accurate pressure reading was good. possible to say can measure in pipe line and how much diameter pipe can measure using your product.
(Sept 18, 2014) D said:
Do gauges lose accuracy if they're water logged?
Almost certainly, as the water will corrode the pressure gauge internal moving parts.
Watch out: a water-logged pressure gauge on a water system is also at risk of bursting and causing a water leak in the piping system.
Question: water pressure gauge indicates water tank is gaining pressure: why?
(Nov 23, 2014) scott said:
am I getting false pressure reading or is the water tank gaining air presure
Gee Scott, I can't guess from just the question and no idea about what equipment is installed. If the gauge pressure seems to be creeping up I suspect a pressure switch problem, an air volume control problem (gaining air as you suspect), or a gauge that's sticking.
If an independent water pressure test - say using a portable pressure gauge at a hose bib or washer hook-up confirms that the static (no water running) system pressure is increasing abnormally or if you see abnormally high pressure readings at the air valve on an internal-bladder pressure tank, there may be a pinhole leak in the bladder that for a time can result in abnormally high tank pressure. Ultimately that defect should also show up as a water-logged pressure tank and short on-off cycling of the pump.
Watch out: overpressurizing a water tank can cause it to burst - injuring someone. Be sure that your tank has a pressure relief valve installed even after troubleshooting this question.
12/4/2014 Eric said:
Hi. Wonderful collection of information. I have a 4" metal casing well. Iron Filter and Kinetico Dual Tank Softener. 33.4 Gallon Challenger Pressure Tank. Last week, there was an issue with my Iron Filter Control and after my well company fixed the issue and we were back washing the filter, the tech noticed that my pressure gauage went well down to about 25 PSI (I have a 40/60 PSI Pressure Switch).
He commented that there might be a problem with the Well Pump. I have monitored the Pressure and noticed that I haven't had that problem during regular use. I tested how long it takes the well to fill the pressure tank, and it takes about 195 seconds. That equates to about a 10 GPM flow. That "seems" like it should be fine for the Backwash requirements of the Softener & Iron Filter. Pressure Gauge and Pressure Switch are from 2007. Pressure Tank is from 2009.
#1) After shut off, does the pressure (on the guage) go down gradually as water is being used? (i.e. 1.5 Gallon Toilet fulshed 5 times uses 7.5 Gallons of water, so I should see an appropriate loss of "pressure" showing on the guage?)
#2) How much of my 33.4 Gallon Pressure Tank is used up before the PSI gets to 40? Is it actually all of that water? or is it just a percentage?
#3) What other "self checks" can I do to better understand if my system is running properly? Thanks in advance for youe help.
Yes Eric, as you use water air in the pressure tank pushes water out to supply the building the in-tank and in-system pressure drops until it reaches the cut-in pressure set on the control. Then the well pump then turns on and re-pressurizes the tank back to the cut-out pressure.
But water volume estimates that you ask about are difficult to measure if the pump runs while you are also using water. In that case some pump output goes to the plumbing fixture. And if water is run faster than the pump can send water, water flow rate falls to equal the pump's output rate in gpm.
At more reading above try the article on WELL FLOW TEST PROCEDURE
If the draw-down water volume becomes noticeably small or the well pump cycls on and off frequently then we suspect a water-logged pressure tank. In that case see SHORT CYCLING WATER PUMP and
then see WATER TANK AIR, HOW TO ADD
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