Water pressure gauge accuracy questions and answers.

This article series 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.

How to Read Water Tank Pressure or any Pressure Gauge Accurately

These questions and answers about the accuracy of water pressure gauges (and some air pressure gauges) were posted originally

at WATER PRESSURE GAUGE ACCURACY - be sure to reveiw that material.

On 2020-12-13 - by (mod) -

Lee

It's possible that your pressure gauge is stuck and therefore not registering correctly.

You might also try opening a faucet in the building to see if in fact any water is being delivered. That would also relieve any unusual pressure. Frankly I don't know what would produce 120 PSI of pressure at an ordinary home Pump and Well system so I suspect the gauge is defective.

What I would watch for with great care is turning on water if the pump itself is frozen or if piping supplied to the pump is frozen. Either of those can damage the pump itself. So when you are ready to turn power on be ready to fend off quickly if you hear the pump motor humming but not running or if no water is delivered.

On 2020-12-13 by Lee

I had a pipe in well house to freeze and burst, replaced pipe but the pressure gauge now reads 120, an afraid to turn water breaker back on. Any advice on why it is now registering that high and what should be done. Thanks

On 2020-10-24 2 - by (mod) -

That pressure range is standard;

But if you are having to re-engage the pump; I suspect that your water draw is exhausting the well, and a pump pressure protection device is shutting off the pump - since if you run the pump dry it will be damaged or ruined.

We explain that control at WATER PUMP PROTECTION SWITCH

But the actual problem is an inadequate well.

In the article index find WELL YIELD IMPROVEMENT

On 2020-10-24 by Diana

We have a new bladder tank set to run from 40 - 60.

The pressure gage drops to 0 quite often and we have to manually engage the pump. This occurs mostly when the washing machine is running. What are common reasons this could happen. The gage is also new. Can debris in the line cause this?

On 2020-07-28 by Hal

Hi. I just dialed in my home water pressure, to 42lbs-62lbs. It had fallen down about 2 lbs. in range, fairly quickly after the same calibration a few months ago. Now I'm 2nd guessing myself. It's 7-28-20 now, and it's been hot, around 100 daily, for several days.

Is it possible for my pressure gauge to be off a hair when it's hot ? It's a pretty nice gauge, oil filled, solid. Does warmer water itself change the equation at all ?

Thank you, Hal

On 2020-07-01 - by (mod) -

Jenifer

Check the gauge pressure at the pump or water tank.

Is the pump coming on at the cut in pressure set on the pressure control switch?

Typically that's 20 psi or 30 psi.

On 2020-07-01 by Jenifer Bahney

water pressure is low after flushing toilet

On 2018-08-20 by (mod) - If water pressure drops quickly when you open a faucet

If pressure drops quickly when you open a faucet, probably the pressure tank is water-logged.

Separately, if the pump turns on when it should but does not deliver water I would look for

- a debris-clogged strainer or foot valve

- leaks in well piping

- low voltage to the pump
- a damaged or worn pump impeller

- low flow rate into the well

On 2018-08-20 by Brent

Point well with pressure tank and jet pump. Turn water on (decent pressure with gauge reading 50). Pressure drops to 30 and pump comes on, but water pressure drops to almost zero with the pump running.

If I shut the water off, pressure will build again and cycle repeats. I haven't lost water flow altogether but it drops to where I cannot maintain a steady flow.

Gauge is shaky, not steady and drops from 20-0 very quickly.

Pressure tank is 28psi. Could I have a clogged line to/from pressure gauge, or a defective gauge? Any other ideas?

On 2017-10-19 by Mary Ellis

I have a air bladder water tank, what is the pressure suppose to be? I have low pressure to house..I have a gage like the one shown above...

On 2017-07-20 by (mod) -

No Peter, a bad water pressure gauge itself will not interfere with water tank operation: it's only a pressure indicator, not a control.

However, IF the gauge is not working because of debris clogging of the gauge port, that same debris could be fouling up other water system controls like the pressure switch. And if no water is entering the water tank there's more likely a different problem such as a bladder stuck to itself.

See https://inspectapedia.com/water/Water-Tank-Bladders.php where we describe the stuck tank bladder problem.

On 2017-07-20 by Peter Stewart

My guage is not working. Will this cause my holding tank to not refill. I seem to be getting decent flow from pump to my house. But bypasses my tank.

On 2017-07-12 by (mod) -

Joe:

Great question. I am SPECULATING that after you changed the pressure regulator you read the gauges before running any water - so the system remained pressureized to the previous level. If you adjust the regulator downwards then you should see the system stabilize at a lower pressure once you've run some water.

Wendy:

the tank, when fully drained, is pre-charged to 2 PSI below your water pump's CUT-IN pressure. I don't know what switch your pump uses nor its pressure setting so I can't give a number.

On 2017-07-11 by Joe

I put a new Watts pressure gauge at three different spigots in my house each time it read 78 psi.

Then I turned the adjusting bolt on my pressure regulator and clearly reduced the water pressure in the house, but the gauge readings never changed. Thinking I had a defective gauge, I bought another (identical) one . Exact same reading -- 78 psi. How is that possible?

On 2017-06-27 by Wendy

How much psi goes into a 20 gallon bladder tank?

On 2017-04-12 by (mod) -

Randy:
With pump off and pressure drained from the system the tank pre-charge pressure needs to be 2 psi below the pressure control switch CUT IN pressure. That's a good starting point.

On 2017-04-09 by Randy

@joel, sounds like a air tank problem no air check the air in the tank if it keeps losing air your bladder has collapsed. If not that your well pump is weak.

On 2017-04-09 by Ranxy

I have a new 20 gallon air pressure tank. Do I reduce air in it after it fills with water . Cause I checked it after it filled up water now it reads 40 to 45 psi. I only suggest air at 30 psi. What should I do.

On 2017-03-25 by (mod) -

Most likely there is a bad check valve, maybe a bad backflow valve, or possibly there is a leak somewhere. I'd start by looking with great care for a toilet that runs without notice.

Search InspectApedia using the box just above to

find TOILET RUNS CONTINUOUSLY to see those details.

On 2017-03-25 by Skip

I have a supplementail water pump on my village water due to low pressure. It has a 6 gallon bladder tank. The pump comes on with a one gallon use and periodically with no use of water. I have a spring backflow value before the pump. Why would this happen?

On 2016-05-30 by (mod) -

Re-posting
AUTHOR:Terry (no email)
COMMENT:Is it normal to have water in the water pressure gauge?

Reply: no the gauge needs replacement.

On 2016-05-02 6 by Barbara

We have a private well. The pressure gage shows 40 but we have no water throughout the house. I looked for a relay switch (we just bought the house in October) I can't find it. What could be causing this and how do we diagnose it.

On 2015-07-20 by Lisa

My check valve on my well is very loud. I replaced it because it failed 1 1/2 years ago along with the starter capacitor. It has been steadily getting louder. I am planning on pulling the pump this fall since it is the original pump from 1975 and I want to replace it before it dies on its own without warning. Is it a faulty check valve? It holds the water pressure but it is just getting so loud. I continually check all my pressures.

On 2015-07-06 by (mod) -

Juan a tripping breaker means it's doing its job trying to prevent a building fire from overheated electrical components. I suspect your pump is overheating, drawing high current, causing the trip-off.

On 2015-07-06 by Juan

I was filling above ground pool and well breaker keeps going off. Turn on but water pressure is low. No water at the moment.
Juancarlosdom1@hotmail.com

On 2015-04-27 by (mod) -

Joel

The problem could be any of several causes: loss of water in the well, a leak in well piping, a damaged pump, even low voltage. Short cycling of the pump on and off as you describe usually means that the pressure tank has lost its air charge. In turn, short cycling can damage a pressure switch or pump motor.

On 2015-04-27 by joel

what if my water pressure gauge that is in my line in front of the tank in reading 0 and i have very weak water pressure? is that a problem with my pump? i have a well and the pump is outside down in the well, but the switch turns on and off repeating every few secounds when someone is using water in the house.

thanks

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+

Reply:

Pressure gauge readings at or over 100 psi?

With ANY pressure gauge, if you subject it to a pressure higher than the gauge scale can indicate, the gauge is

- 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?

Reply:

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

See WATER PUMP SHORT CYCLING - home

We also provide a comprehensive ARTICLE INDEX to RELATED ARTICLES that includes a live link

to - WELL WATER PRESSURE DIAGNOSIS - home

and below that are several more articles on the diagnosis and repair of a water pump that is turning on and off rapidly.

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.

Reply:

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 bottom in the ARTICLE INDEX titled WATER PUMP PROBLEM DIAGNOSTIC TABLE
see the article titled:

SHORT CYCLING WATER PUMP

and below that are several more articles on the diagnosis and repair of a water pump that is turning on and off rapidly.

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.
What's problem?

Reply:

Julliet,

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

-- there is a leak in well piping

-- the pump has internal damage

-- the gauge sensor port is not sensing water pressure properly due to improper installation or debris clogging

- 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?

Reply:

D

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

Reply:

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.

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.

hat 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.

Questions:

#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.

Reply:

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.

In the ARTICLE INDEX found among the Continue Reading links at the end of this article 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

Question: inconsistent pressures at different locations in the water supply piping system

(Jan 31, 2015) Bob said:

I have 85lbs before the presure tank and when it gets to the house it's down to 40 what do I need to do

Reply:

Bob,

If no water is running at the house then you should see identical pressure everywhere in the system unless

- there is an intermediate water pressure regulator

- there are leaks somewhere

 

...

Continue reading at WATER PRESSURE GAUGE ACCURACY or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• WATER PRESSURE GAUGE INSTALLATION
• WATER TANK PRESSURE GAUGE for details of how to repair or replace a water tank pressure gauge.

Suggested citation for this web page

WATER PRESSURE GAUGE ACCURACY FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to WATER SUPPLY, PUMPS TANKS WELLS

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