Meter spinning backwards and air in line

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  #1  
Old 10-29-11, 11:23 PM
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Meter spinning backwards and air in line

Hello,

Over that past 2 months or so I have noticed every time I open a faucet or start a load of laundry after there has been no water usage for over an hour, I hear air spitting out of the faucet or in the washing machine when it is refilling. I just figured it had to do with them replacing all the water lines in my area due to age and deterioration and that air had just gotten into the lines. It has been at least 3 months since the work was completed so I figure something else has to be going on. Every few months I take a look at my water meter at the road to compare the readings to my bill and this last time I noticed when there is no water being used on my property, the little pinwheel in the middle of the meter will spin backwards for about 10 seconds, than stop for a few and than spin in the opposite direction before stopping and repeating the whole cycle over again. I have been noticing that this does cycling does not stop at all no matter what time of day so I started looking for a cause. When I turn my main water valve at the road off, all cycling ceases. I checked each valve in my house before finding out that when I turn the hot water inlet valve off, the cycling stops. When I open it again, it resumes. I have an expansion tank installed to prevent backflow and I took it down to check the air pressure and it was at the 40psi that it said was a pre charge from the factory. Why would the hot water tank be causing backflow if the exp tank is supposed to prevent this? Also why did this just suddenly appear over the past few months. I have never noticed this before in the 4 years I have lived here. Is this something I need to have corrected or is it not that big of a deal? Isn't the water meter supposed to have a check valve in it anyway to prevent this?


Thanks for everyone's help in advance.



-Paul Miller
 
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  #2  
Old 10-30-11, 07:16 AM
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The expansion tank does not prevent backflow. Only a check valve will do that. You need the expansion tank if you have a check valve.
 
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Old 10-30-11, 07:44 AM
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Most municipal systems will require a back flow preventer. I know in my community they sent everyone a notice to have one installed as it was not part of the meter. With the expansion tank holding a pressure on your side of the meter, any time the line pressure drops below that 40 psi, water would flow the other direction. Less than 40 would be a rather low line pressure, but possible, and would vary and demand down line varied.

Not a pro, just my thoughts.
Bud
 
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Old 10-30-11, 10:58 AM
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Thanks for the info. I thought the exp tank prevented backflow from the hot water tank, thanks for correcting me. I guess it is to keep the tank from exploding or constantly triggering the relief valve in a closed system? What are your thoughts on air in the line then?


Thanks,

Paul
 
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Old 11-01-11, 05:12 PM
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Not a pro, but seems to me if you 1) have an expansion tank, and 2) do not have a backflow preventer, the expansion tank will in effect be connected to the street water system, and will try to maintain the street pressure at its equilibrium pressure. So, every time the street pressure drops a little, the expansion tank tries to compensate. Because the expansion tank volume is tiny compared to the street volume, small changes in street pressure would cause relatively large changes in expansion tank volume. What you may be seeing is the filling and emptying of your expansion tank through your water meter.
I would either remove the expansion tank or install backflow prevention. Seems like you will wear things out (especially the exp. tank) if you don't deal with this. Not sure why you have air in the system.

Again, not a pro. Can anyone confirm this guess?
 
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Old 11-01-11, 07:31 PM
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Most municipal systems will require a back flow preventer. I know in my community they sent everyone a notice to have one installed as it was not part of the meter.
New water meters in my area now have a check built into them. I never had a problem with my water heater increasing the system pressure in my home till the last time the water meter was changed. My Watts PRV has a bypass and doesn't prevent backflow.
 
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