Fire Line issues 4

[jjclinton]

We have a 12" fire line from the city. It also has another input from the city on the other side of the plant from a different city main. The city has a flow meter attached to this main that begins right before a double back flow preventer and inserts right after the preventer. This meter is showing flow at a rate that fluctuates, but is about 15000 to 50000 gallons per month. It seems to show increased flow during the winter/spring time. Since this is a closed system we should not have any flow. We have hooked our ultra sonic flow meter to this line and are unable to get any flow to appear. We also have no signs of leaks any thoughts would be helpful. It may also be helpful to note that we are located in the midwest so we see season fluctuations in our temps.

 

[bimr]

Sometimes the utility companies will use estimated readings, and then do an actual reading of the meter at some future time. I have seen crazy billing when the estimate is way over what the meter is reading - in this case the bill is erroneous and you can request to send them an actual reading.

If the meter reading is not estimated, then the meter is faulty. Request that the utility recalibrate the meter.

Where deposits are expected in any flowmeter, the meter should be regularly inspected and cleaned as per the experience gained during the course of time. As these deposits affect the accuracy of the measurement, Vortex meter, Magnetic flowmeter, Ultrasonic flowmeter, may show erroneous reading in the presence of deposits. In an intermittent water supply the corrosion rate of the pipe increases due to chlorine and air. The formation of incrustation and subsequent descaling affect flowmeter working especially differential pressure type, turbine meters.

 

[coloeng]

I would think that you have a double check on both connections to the city water system and from your post only one side is metered. If you are positive that you don't have any usage or leaks within your system, you should make sure that the double check that is not metered is operating correctly, have it tested. If it is not operating correctly and is allowing backflow out of your fire system, the difference in pressure from one side of the plant to the other could be responsible for the metered flow that is being seen. If the double check tests ok and you are positive there are no leaks, then you need to make sure that someone isn't using the water for something unauthorized within the plant.

 

[jjclinton]

coloeng that is one of the theories that I had thought of as well. I think that we will pursue that idea a little deeper than we have already thanks for the post.

 

[cvg]

you are talking about a fraction of a gallon per minute. It's possible one of the checks is not sealing tight allowing this "nuisance" flow through.

this small amount of flow could also be explained by a small leak in your fire line which could easily go undetected and virtually undiscoverable (assuming the line is underground) without calling in Sherlock Holmes.

 

[stanier]

Could there be waterhammer in one or both lines that cause the meter to give such readings?

Does the utility run routine pump tests that could cause such events?

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/