Does having an Expansion Tank on your Water Heater make the water meter move?

Hi there. I just moved into a new home and got hit with an incredibly enormous water bill. I checked my water meter and could see the little dial moving - not all the time but every 10 seconds or so it would move forward. Sometimes it moves backwards but never enough to make up for the forward movement. I have made sure all water is off in the house and have done visual checks for leaks as well as a dye test in the toilets. I called a plumber over and he said this motion is caused by the expansion tank on my water heater. Low and behold when he turned off the expansion tank the motion stopped completely. He told me that this is normal for expansion tanks to cause this motion - however he said the movement forward and back should be equal. I have not noticed this. Can anyone verify if their expansion tank causes the same forward motion on the meter?
thanks so much.
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Cameron wrote:

I suspect you need to talk to the water company as the meter should be neutral to any effect from the expansion tank.
--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math
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Cameron wrote:

<SNIP>
The whopper bill could have been due to some billing fluke during the transfer of ownership. As Joe said, take that up with the utility. And see what the next reading is. Or, take your own readings, day-by-day.
I cannot think of any reason why the exp tank would cause meter movement every 10 seconds. I'm not doubting that it stopped when he closed off the exp tank, but it doesn't add up yet.
I think I'd start by measuring daily consumption. If you can, make a measurement over a long period when no one is at home (and no water being used).
Jim
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Probably a leaking toilet, or worse yet, a breach underground going from the meter to the house.

A pressure reducing regulator on the utility mains upstream from a residential neighborhood might cause the above to occur--if you had a pressure guage on the line you would see line pressure changing from a high to a low reading on a frequency dependant on total volume of inflow feeding the entire neighborhood.......however, this is unrelated to the whopper water bill mentioned above......
--

SVL





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PrecisionMachinisT wrote: ....

Well, if the meter is reading a small quantity flow and only reads one direction if the pressure is changing, each increase in pressure would mean some flow past the meter and each reduction would mean a reverse flow. I don't think meters are generally sensitive enough to pick up that amount of flow, but I could see how it might under just the right situation.
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Joseph E. Meehan

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Ask the water company to check the meter.

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Cameron wrote:

Something doesn't sound right. The expansion tank is there to allow the hot water in the heating system to remain full without any air in the lines. In order to do this the expansion tank has a bladder that is charged with air(except very old tanks which do not have a bladder). As the hot water expands it displaces this bladder and the pressure in the heating system remains relatively unchanged. When the tank looses its charge and the furnace turns on to heat the water, the water will expand, have no where to go, and will leak out of the temperature/pressure relief valve. In this case you would be seeing a leak from this T&P valve and the plumber should have recommended replacing the expansion tank. Why he didn't recommend this, and why you didn't see a leaking T&P valve, just doesn't add up. In addition to that, I doubt if the meter is sensitive enough to show this relative small rate of usage. Here is a test you can try for yourself. Turn off the same valve that the plumber turned off. It would be the fill valve to the furnace and is usually located just before a pressure regulator. Verify the meter has stopped moving. Incrementally open a sink faucet until the meter moves at the rate you have been seeing before. What is the flow rate? Measure it by timing how long it takes to fill a particular volume container. I'm guessing it will be at least 1/3 gallon per minute. My guess would be like the others have mentioned, leaking toilet, leaking outside faucet, or a leaking underground feed to a auxiliary structure like a pool house.
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