What is driving me a bit not sure recently is that the water meter leak indicator sometimes can move a bit over a long period (say an hour or a few hours). My water meter is a Procoder meter same as below.

I guess the smallest interval for the red leak indicator is 0.0001 cf which is about 0.1 oz or 2.8ml. Not sure if my reading is correct.

The red indicator sometimes can move a few intervals (~10ml) over a period of a few hours. But sometimes it just makes no movement over a period of a few hours. I wonder whether this is acceptable?

I cannot figure out what is happening. I do have a 40 gallon water heater and a water expansion tank (2.1 gallon). I sometimes wonder whether it can be just temperature fluctuation which causes either the water or the air in the expansion tank to contract/expand. Any suggestions?

Btw, I am doing this because the house had some pipe work and garden sprinkler lines done recently, and I am checking for possible leaks.

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  • 3
    Why are you worried about .0001 cu ft yes it could be a leak it could be your toilet or water heater expanding beyond the capacity of your expansion tank I would be wondering if the pressure (water heater) caused is creating an apparent leak but there is not one, check valves leak meters are not exact them selves. Ok you have less than a oz after a couple of hours if that’s all it takes to drive you crazy maybe you should not be watching the gauge
    – Ed Beal
    May 11, 2021 at 21:06
  • I had no idea what amount of leak is acceptable and not entirely sure if my reading of the meter has been correct. If the indicator moving a bit in a few hours is acceptable, then thanks I know it is OK now.
    – max sim
    May 11, 2021 at 22:13

2 Answers 2


Max, with that small of a “leak” I would not worry about it but I may try an experiment where you turn your water heater off for several hours and see if it is any different this test may be more accurate if some hot water was used after the water heater was turned off so the cooling down or cycling of the water heater might be eliminated as the cause but .0001 cult is a very small amount of water. And probably not worry about as it is not a consistent leak and may be due to water heater temp cycling.

  • OK. I dialed the water heater back to "pilot" and used up the hot water. The leak indicator no longer moves even after 5-6 hours. The heater seems to still heat the water to keep it warm (and I wonder why...), but not as hot as before. I guess the lower temperature significantly reduced the cooling down & contraction.
    – max sim
    May 14, 2021 at 18:47
  • That is what I expected, water meters usually only can detect flow not direction, it is possible the higher temp was pressurizing the ex pan toon tank to the point the check valve was leaking or a leak somewhere. Checking at the lower temp with no leakage shows that was most likely the case.
    – Ed Beal
    May 14, 2021 at 19:06
  • That is possible. But I was checking expansion tank, the pressure stayed within 5 psi above/below the incoming water pressure. So I am thinking it can be just that 40 gallon water cooling down and contracting. A bit calculation shows losing 5 degrees can cause about 0.02 gallon contraction. Make sense?
    – max sim
    May 15, 2021 at 16:50

Turn off all water sources in your home or building, including faucets, showers, toilets, and appliances. Check your water meter reading and note it down. Wait for a few hours without using any water, and then recheck the meter. If the meter reading has changed, it indicates a leak in the system.


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