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Context: If I understand the plumbing in my garage correctly, the white lever turns off water flow to my front hose bib. Notice the blue sticker behind the level saying "front hose bib valve". Further, the white lever is turned horizontally, so no water should be going to the front hose bib.

Front view of plumbing

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Side view of plumbing

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Plumbing during construction

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Concern: Above the white lever is a orange lever connected to a water pressure meter. When I opened the front hose bib this morning (to ensure there was no water coming out), the pressure meter dropped to 0. But since then, it's slowly rising back up - at last check, it was at 20 psi.

Question: Is the water pressure meter indicating that water is going to the front hose bib despite the white lever indicating the valve should be closed?

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    Is heat/sun hitting that section of pipe between valve and hose bib? Why do you have so many pressure gauges? Pressure gauge/meter measures pressure, air or water. If you opened hose bib and no water came out, then possible air is causing increase pressure.
    – crip659
    Commented Dec 26, 2021 at 22:28
  • When you close the white bib valve, the water remains full in the pipe segment with the same pressure as just at the closing. If you want the gauge to go to zero, you need to bleed the water, or turn the gauge valve (orange handle) off.
    – r13
    Commented Dec 26, 2021 at 22:41
  • @r13 - But I opened the hose bib after closing the white valve so there shouldn't be any water in the line.
    – Craig
    Commented Dec 26, 2021 at 23:15
  • Try this - leave all valves open and drain the line, then take the reading on the gauge.
    – r13
    Commented Dec 26, 2021 at 23:28

3 Answers 3

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This is as it should be. You are measuring pressure not flow. Assuming the pressure gauge is OK: if you pressurise the line to the hose bib, have the bib turned off when shutting off the feed valve it will not change the pressure that is in the line, if it did you would have a leak. When the bib is vented (open the bib) and it will go to zero. If the temperature changes the pressure will also change per Boyle's law. For example: A pressure tank for a water system is basically a tank with air on top to maintain pressure, they work great and do not leak unless they have failed. The same thing can be applied to shock absorbers where a line is run vertical with water coming in the bottom and the top sealed. I have several in my home and every few years I need to drain them because the water will eventually dissolve the air.

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  • This morning, I closed the white valve and then opened the hose bib so I'm expecting all the water in the line is drained. If that's the case, I'm still confused as to why the pressure would later rise. Is the meter measuring water pressure behind the valve, or perhaps air pressure in the line? Note that it's below freezing in my area so I want to be sure the line is winterized. Please note - I'm not trying to be argumentative; I really want to understand.
    – Craig
    Commented Dec 26, 2021 at 23:14
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    If the sun is hitting the hose bib, it could raise air pressure in the short line enough. If hose bib is left open, pressure should not rise.
    – crip659
    Commented Dec 27, 2021 at 0:01
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Without changing anything else, go open the hose outlet again - either it has water, meaning the white valve is leaking, or it does not. Leave it open with a bucket under it. If the bucket becomes more full over a day or two, you definitely have a leak at the white valve.

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With the hose bibb closed and the white valve closed, sunlight hitting the bibb will warm the air inside the pipe and increase the pressure in that section of pipe.

Check the pressure first thing in the morning (sitting over night, no sunlight, the air has cooled), then check it in late afternoon (warm sun beating on the bibb all day). You'll probably find the pressure low to zero first thing in the morning, then higher late in the afternoon.

Either that or your white valve is leaking and Ecnerwal's fine answer will tell you how to determine if that's the case.

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