Water Meter spins forwards and backwards continuously


Old 08-31-15, 09:06 PM
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Water Meter spins forwards and backwards continuously

Hi, I have wondered about this for a few years now and hope maybe someone can explain what is going on.

My house is 8 years old and for at least 3 of them I have heard this repetitive knocking sound in one of my walls. I can also hear it near the hot water tank. Didn't think much of it when I first noticed it. Then one day I was looking for a shut off by the water main meter and I noticed it spun back and forward for no reason. Just to make sure I had nothing running I shut off every shutoff valve by toilets, sinks, washing machine, etc. and it continued to spin the same. I then killed the main valve to the house and it stopped. When I turned main back on it started up again. I finally traced it back to if I shut off the main to the water heater it finally stops.

With that said I figured maybe it was the expansion of hot water fighting with the city pressure, I have an expansion tank, wouldn't that prevent this? Also, why doesn't the meter have a check valve?

I figure this is something that needs to be corrected but not sure how. Any input would be appreciated.

I posted a video of what the meter looks like while doing this below.



Last edited by PJmax; 08-31-15 at 09:18 PM. Reason: fixed link
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Old 09-02-15, 01:38 PM
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In general, what you're seeing is normal. As pressure changes in the water main, the pressure will equalize in your house, causing the meter to fluctuate a bit back and forth. You'll often see this when someone on your block turns on their sprinkler system, or a fire hydrant is opened.

That said, I've never seen it happen quite that much. Do you have a pressure reducing valve (PRV)? It looks like a brass cylinder next to the meter? I'm surprised you have an expansion tank if you don't have a PRV, I've never seen that setup before.
Old 09-02-15, 06:13 PM
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Does that mean if you pumped water from a river or pond into the water main that you could not pay for water?
Old 09-02-15, 06:48 PM
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Water does not compress noticeably.

Because you have an expansion tank, fluctuating pressure in the water main will cause more seesawing of the water meter compared with no expansion tank. With all faucets closed, pressure in your house will stay approximately the same as the water pressure outside your house. The air cushion in the pressure tank will grow and shrink depending on the pressure causing water to exit or enter the pressure tank and causing flow through the meter.

You don't have to fix anything. The water company may choose to install a check valve and then the seesawing of the meter will stop.

Last edited by AllanJ; 09-02-15 at 07:07 PM.
Old 09-02-15, 08:01 PM
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Thanks everyone that replied. I have never seen a PRV anywhere on my system. I have seen them before so I know what they look like. When the house was built 8 years ago I remember the plumber saying I might need one but the city pressure fell in the acceptable range and they never added one. The expansion tank was and still is a code requirement if I was told correctly for ALL hot water tanks in my county, maybe in the state so that's how that came into play after they originally failed inspection for not installing it.

I was just worried that something may come up in the future because technically the water after my meter on my side is going back into the main and returning which would be considered a backflow I would think.

Also that is such a miniscule amount of water, however over a month or so is it possible that could add up to any extra use charges? I doubt it would be much, just curious if when the low flow dial spins backwards if it still adds to the forward spin of the main dial over time.

Thanks everyone,

Old 09-02-15, 08:08 PM
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I would imagine that the meter spins in the plus direction more than in the reverse direction. You shouldn't notice any change in your water usage or bill.

I am curious about one thing. Usually when an expansion tank is installed on a hot water heater... there is a check valve between it and the cold water supply. Is there not one in your setup ?
Old 09-02-15, 08:16 PM
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Doesn't look like it but here are some pics...
Name:  20150902_211200.jpg
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Size:  21.4 KB

Name:  20150902_211215.jpg
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