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Expansion tank causes meter to turn?


Lasswell
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I have been a home inspector for 8 years but this one has me stumped. I have searched the web and found nothing so I though I would try here.

I own a new house which is vacant and for sale. I just received a water bill that showed I was using 40 gallons per day. I checked the meter and sure enough it shows water is flowing at the rate of about 1.5 gal. per hour. The meter does not register a constant flow but stop and starts in 10 second intervals.

I went around the house shutting valves off until I was able to isolate the problem to the hot water system. When I shut the supply valve for the hot water heater the meter stops turning. I went through the house from top to bottom and no signs of moisture. I even scanned all walls and ceiling that had plumbing runs with a moisture meter and nothing so I called the plumbers who plumbed the house. They also could't find anything so as a last resort we removed the expansion tank from the water heater and low and behold this stopped the problem.

I called my local utility and they sent a crew out to check the meter and I was told the check valve in the meter is working properly and my problem was a leak in the house?

Anybody ever run across this before? My theory is the pressure is fluctuating in the line and with the expansion tank pushing back against the line pressure the fluctuations are forcing water back and forth through the meter causing the reading. My local utility of course says this is not possible.

Any help would be appreciated.

John

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The pressure relief line is visible and I have checked it several times and it has always been dry. It discharges over an area of beauty bark and there are no signs it has been discharging water.

One thing I didn't mention is the water heater is turned off because the house is vacant.

John

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That's a good one alright.

Do you have a lawn sprinkler system? Do you have a water softening system in the home? Any chance of a cross connection with a toilet running (it can happen). A faulty solenoid valve on a humidifier?

Your theory of the pressure fluctuating back and forth causing a problem is highly unlikely however. The thing I don't know for sure is if the water meter will record in reverse (kind of like driving a car in reverse and the odometer gig). You could put a check valve in the main water line to test your theory.

With regards to the expansion tank: it is only there to allow the expansion of heated water some place to go (but you knew that already). Shut off the gas, or the electric, to the hot water heater tank and allow the water to cool - does the problem go away?

Hopefully some food for thought. I dig problems like these - keep us posted.

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One thing I didn't mention is the water heater is turned off because the house is vacant.

John

Well... then the expansion tank really isn't a concern (with the exception of high incoming water pressure).

Did you measure the incoming water pressure at a tap? Too high of an incoming water pressure will cause toilets to keep flowing.

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Terry,

I did check the water pressure at it was 82 psi so marginally high.

The thing I can't figure out is if I remove the expansion tank and put a pipe plug in the fitting and turn the water back on the meter does not turn. As soon as I put he expansion tank back on the meter starts turning.

John

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Terry,

I did check the water pressure at it was 82 psi so marginally high.

The thing I can't figure out is if I remove the expansion tank and put a pipe plug in the fitting and turn the water back on the meter does not turn. As soon as I put he expansion tank back on the meter starts turning.

John

I ain't got a definitive answer, but you get my vote for the most interesting query in years.

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Terry,

I did check the water pressure at it was 82 psi so marginally high.

The thing I can't figure out is if I remove the expansion tank and put a pipe plug in the fitting and turn the water back on the meter does not turn. As soon as I put he expansion tank back on the meter starts turning.

John

82 is pretty high. You really should install a PRV on the main.

A stretch - perhaps the expansion tank is allowing for a higher pressure before pusing back?

Also, a pain in the a$$ but you could shut off everthing in the home, toilets, sinks, the whole system except the main water shut off to see what happens. Then it is process of elimination.

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I new the pressure was on the high side and I am planning on installing a pressure regulator.

Terry, I have tried shutting off every angle stop and valve and that is what led me to the hot water system and the expansion tank. Removing the expansion tank then turning the water back on is the only thing that stops the meter. Why this works has left both me and the plumber scratching our heads.

John

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Do you have a neighbor with a swimming pool?

- Jim Katen, Oregon

That's an idea. Got any interior shutoffs for your exterior sillcocks? Turn them off for a month and see what happens.

Maybe the neighbor is hooking up a hose to your house at night to sprinkle his lawn or wash his car.

Hee, hee, maybe he's tapped into your line below grade. [:-eyebrow

If I ever caught a neighbor doing that, I wouldn't say a thing; I'd cut into the line, fill an expansion tank with some bright yellow paint, and then hook it up to my air compressor and wait for the fun to begin.

ONE TEAM - ONE FIGHT!!!

Mike

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A few years back I was inspecting a home for a gal who's father was a city water dept. manager. He was really concerned about the expansion tank and whether there was a check valve in the system. He explained to me that in his city, water meters where providing erroneous numbers (over charging people). The cause was leading them to believe the expansion tanks were causing the water to pulse therefore making the meter tick up. He said the meters where not designed to run backwards. He was currently battling with the city code enforcers about expansion tanks being required on all newly installed water heaters without check valves.

Ok, now that I have said all of that, I don't know what the end result was or if his conclusions were ever verified. However reading about your process of elimination I would be highly suspicious of the expansion tank and whether the check valve is truly working.

Oh the city was Bellevue WA and it was approximately 4 years ago.

Mike

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A few years back I was inspecting a home for a gal who's father was a city water dept. manager. He was really concerned about the expansion tank and whether there was a check valve in the system. He explained to me that in his city, water meters where providing erroneous numbers (over charging people). The cause was leading them to believe the expansion tanks were causing the water to pulse therefore making the meter tick up. He said the meters where not designed to run backwards. He was currently battling with the city code enforcers about expansion tanks being required on all newly installed water heaters without check valves.

Ok, now that I have said all of that, I don't know what the end result was or if his conclusions were ever verified. However reading about your process of elimination I would be highly suspicious of the expansion tank and whether the check valve is truly working.

Oh the city was Bellevue WA and it was approximately 4 years ago.

Mike

The expansion tank is a can with a bladder and a pressure charge.

expansiontankfig3a.gif

Once the pressure is stabilized in the building it just sits there.

Are you saying that the incoming water pressure is/was pulsating and that the expansion tank was pushing the water back out into the street? Then the water meter, not being able to run backwards, did not register the water going back out however did register the inrush again? I guess anything is possible but that would be a new one on me.

Does anyone know if a water meter can run in reverse (I do not)?

Also, if the water meter was defective you'd think that it would do it regardless of whether the expansion tank was present or not. Perhaps the water department can monitior the pressure for a few days and record the results.

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That's a good one alright.

The thing I don't know for sure is if the water meter will record in reverse (kind of like driving a car in reverse and the odometer gig).

Water meters will flow backwards with reverse direction lowering the readout of gallons consumed.

I learned this a little more innocently then you might think.

Matt

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That's a good one alright.

The thing I don't know for sure is if the water meter will record in reverse (kind of like driving a car in reverse and the odometer gig).

Water meters will flow backwards with reverse direction lowering the readout of gallons consumed.

I learned this a little more innocently then you might think.

Matt

Not that I don't believe you Matt but point me in the direction of backup documention.

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Terrence,

Documentation I have not.

Experience I have seen it.

Rental complex, 6 houses per water meter.

Rental units are on top of a hill, The city cut a main 6" water line about 2 miles away at the bottom of the hill. We were working on running a new line getting some sites ready when we turned on out 2 inch ball valve it was sucking air.

The downflow of the water draining out of the line they cut was sucking the air.

When you open a valve it sucks air back in making the meter spin in reverse while if you open a hot water valve inside the house, it will suck the hot water out of the tank causing the top element to "expire" when it contacts air while on.

We replaced a few elements that day.

Thats about the extent of my experience with it running backwards.

Matt.

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