Water Meter Accuracy

[INTELLECTRIC]

Curious about the impact of turbulence and slightly out-of-level meters; I read on other discussions that the flow wheel is floating in the meter, so any misalignment would cause it to rub, and thus read less than true. However, could turbulence potentially cause a meter to read greater than true?

I have installed six meters in a small commercial plaza to allow the management to divide the costs of the city water service. However, for the first two months of operation, the sum of the meters has been ~6% higher than what the city has measured. I would assume that the city meter would not be as far as 6% out of calibration; is there anything else you have heard that could create this scenario? Analyzing the individual meter amounts has ruled out the possibility of crossover (2 meters in series).

Thanks

[Jameson]

The only way I could think that our EKM meters would read faster than the city water meter would be:

1. If the city water meter is old and the EKM Meters are new. Water meters tend to slow down with time, not speed up.
2. If the EKM meter is measuring air bubbles, but the city meter is not.
3. If you are saying the EKM meter is fast by counting the pulses, and you are measuring water that is flowing in two directions (because of a large air bubble in your system compressing when water gets shutoff, which can cause the water in the water meter to flow in two directions, this is solved by using a check valve), if you are counting the pulses this can result in multiple pulses even though it should not.

To limit turbulence in a water meter you have to install a straight piece of pipe before and after the water meter:

Must have at least 10 pipe diameters in pipe length before the water meter and at least 5 pipe diameters in pipe length after the water meter. For example if you have 1.5 inch pipe and water meter you would want 15 inches of straight pipe before your water meter and 7.5 inches of straight pipe after your water meter. This is to achieve maximum accuracy. If the straight pipe length before and after the meter is less than this, the water meter will still be highly accurate, just not as accurate if you follow the above rule of thumb.

3/4” water meter:
Straight pipe must be: 7.5” before meter and 3.75” after meter

If your EKM meter was installed out of level, it would read slower not faster, so I dont think that is the issue here. If you installed the water meter in such a way that there was a lot of turbulence, I would guess that it would also read slower, but to be honest Im not sure if that is always true.

My guess is your city water meter is old and therefore has slowed down over time, which makes sense. When was the last time your city water meter was removed and re-calibrated?

I hope this helps.

[INTELLECTRIC]

Thanks, Jameson. We will investigate those points, much appreciated!