Question about pressure gauge

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compddd

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We have a pressure regulator and an expansion tank as well as a water softener for our house, when I check the pressure on the cold line on the utility sink in the garage with a Watts pressure gauge, the black needle reads 60 PSI every time, but the red hand goes to 120-180. When I check the pressure on the main line outside before the water softener the black and red needle read 60 every time.

Should I be worried?
 

Reach4

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Vibrations can sometimes move the red hand. Try tapping the gauge to see what I mean.

Your expansion tank should normally be empty. Knock on it to see if that is the case. Do you have a PRV or other gadget between where the pipe for the outside splits off and the inside water? Do you sometimes get some water dripping from your water heater's temperature and pressure valve output pipe?

After you take a hot shower, does the black hand read higher than usual?
 

compddd

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I think you nailed it with the vibrations the utility sink in the garage is pretty flimsy and shaky so I held it steady with my hand and turned it on and now the red and black needle both read 60 PSI.

Thank you Reach4!
 

Jadnashua

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The red needle has a little tab on it so that when the actual indicator rises, it pushes the tattle tale hand up as well. It is then supposed to show the peak reading when the line pressure goes back down for whatever reason. It should not go back down by itself, it should require you to turn the knob, otherwise, it would be useless for the tattle tale function.

If the red tattle tale hand is moving because of vibrations, I'd consider buying a new gauge...it shouldn't be that loose to turn by itself without the main needle pushing it up.

You wouldn't notice the WH T&P valve releasing (assuming it's working properly) until the pressure exceeded 150 psi, so in theory, unless that's sticky, the pressure should never exceed 150 because the T&P should open to relieve it. If it's sticky, it might peak a little higher, I suppose. Too sticky, and it should be replaced.

Follow Reach's suggestion, and verify that the T&P has not opened to discharge a small amount of water after using a moderate amount of hot. The water will expand when it is heated, and if the ET is working, the pressure should not rise much at all. If it isn't, depending on what else may leak (toilets are common and you wouldn't notice unless you heard it since it just goes down the drain), that water normally goes into the ET. Since water doesn't compress...expansion will spike the pressure unless there's something either leaking, or can balloon to take up the increased volume (ideally, that would be the ET).
 

compddd

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After taking a hot shower, should I check the hot or cold side on the utility sink for my pressure reading?
 

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After taking a hot shower, should I check the hot or cold side on the utility sink for my pressure reading?
While I would expect them to be the same, let's say hot.
 

compddd

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Tested the hot after taking a shower and reads 60 PSI on black and red needle. Good to go?
 

Reach4

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Tested the hot after taking a shower and reads 60 PSI on black and red needle. Good to go?
That is what I think.

You can also put the pressure gauge onto the WH drain valve. That should be vibration-resistant.

Another think that could slam the black needle higher would be a brief water hammer pulse. Even if the red needle only jumps to 70 psi momentarily, the red could kick the black and momentum could carry the black higher.
 

compddd

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Back with an update on this. I left the gauge on for a whole day and the red was up to 100 but the black stays at 65. Time to check the expansion tank?
 

Reach4

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100 is OK, even if real. Even if it said 140, (too high) it could be false. Tap on the gauge, and you will see that hand can be vibration-sensitive.

But sure, check the expansion tank precharge. Ideal air pressure is the same as the highest incoming water pressure. I would tend to set it a couple psi higher than the average water pressure to allow for the fluctuation.
 

Jadnashua

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Air pressure gauges and your water pressure gauge may or may not be well calibrated. To check things, at least for a comparison, while everything is up and running normally, check the current air pressure in the ET...if the gauges are calibrated, both the water and air pressure will be equal unless you've overfilled the ET. The slope of the pressure change in the ET is not linear. If the tank is on the small side or you've got the precharge higher than necessary, the pressure will go higher than it will if the tank is larger or your starting pressure is lower than needed.
 

Reach4

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if the gauges are calibrated, both the water and air pressure will be equal unless you've overfilled the ET.
That, of course, is a point we continue to disagree on. If you have city water that changes pressure over the day, I think it is desireable that the expansion tank air be set to the highest pressure from the city, not the low or the random. Setting the precharge less than the water pressure causes the tank to be not empty of water when using the water. Thus there is less room for expansion. Of course a larger tank makes that all less critical.

If you have a PRV, then matching the PRV pressure setting is best.
 

WorthFlorida

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It could be just a spike in pressure when a fixture suddenly shuts the water off and the water hits a wall and recoils. It’s what causes a water hammer effect though you do not have that issue. You’ll hear the recoil in just about any home. At the washing machine when the water is shut off during its use, you’ll see the hoses bounce a little. As others suggested the expansion tank should suppress it but not totally eliminate a short spike.
 

Sylvan

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When gauges start to pulsate with pressure fluctuations (pulsating for example) ideally you need a liquid filled gauge to prevent damage to the bourdon movement

If your street pressure is 60 PSI then the 60 should be the center of the gauge from 0 - 120

Ideally the working pressure in the middle for the most accurate reading
 

compddd

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It could be just a spike in pressure when a fixture suddenly shuts the water off and the water hits a wall and recoils. It’s what causes a water hammer effect though you do not have that issue. You’ll hear the recoil in just about any home. At the washing machine when the water is shut off during its use, you’ll see the hoses bounce a little. As others suggested the expansion tank should suppress it but not totally eliminate a short spike.

I tested by watching the gauge while my wife turned fixtures on and off and it seems you’re correct it spikes when she turns off the fixture. Example: she shuts off the kitchen faucet gently, spiked to 80. Shuts off the faucet quickly and suddenly, spiked to 140. We can hear the recoil as well.
 

LLigetfa

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I assume the gauge you have uses a garden hose thread and that your utility sink faucet has a garden hose thread. You could connect the gauge to the draincock on the hot water tank which should be less susceptible to shock and vibration from water hammer.
 

compddd

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That, of course, is a point we continue to disagree on. If you have city water that changes pressure over the day, I think it is desireable that the expansion tank air be set to the highest pressure from the city, not the low or the random. Setting the precharge less than the water pressure causes the tank to be not empty of water when using the water. Thus there is less room for expansion. Of course a larger tank makes that all less critical.

If you have a PRV, then matching the PRV pressure setting is best.
Is there an easy way to check what PSI my expansion tank is set at?
 

Reach4

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Is there an easy way to check what PSI my expansion tank is set at?
  1. Turn off the water supply before the gauge.
  2. Open a downstream faucet to relieve water pressure.
  3. Measure the air pressure with an air pressure gauge, such as you might use on passenger tires.
 

Jadnashua

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Once you repressurize the system, the air pressure in the tank and the water pressure should read the same unless you overpressurized the tank or your gauges aren't well calibrated.
 

Reach4

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Once you repressurize the system, the air pressure in the tank and the water pressure should read the same unless you overpressurized the tank or your gauges aren't well calibrated.
You keep saying that. You are still promoting wrong info. It is perfectly proper for the air precharge to be a little above the city water pressure.

Now if you were to say the pressures would be nearly equal after the water had expanded enough to raise the pressure above the current city water pressure, you would be close enough.
 
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