Residential Propane Gauges- How well do they work?

Just bought my first house with propane (LP) heat and hot water. What a learning experience. I have a 500 gallon buried tank (didn't realize it was owned by one propane provider and I was locked into that dealer unless I bought the tank) with a guage that reads in percentage. After I signed up for the "keep full" option (thereby saving a dime per gallon), the dealer came out when my tank was reading 59%. I wasn't home when it was filled.
The little gauge on my tank (yes, my tank. I bought it.) moved from 59% to 85%. Subtracting 59 from 85 and multiplying by 500 led me to believe they had pumped in ~130 gallons.
The dealer's printed ticket showed 183 gallons.
Logic tells me that Boyle figured out the relationship to volume and pressure in the 17th Century, and that as the volume of gas (in the void above the liquid) increases, the pressure is reduced and the gauge is a simple pressure gauge.
Dealer said maybe the gauge was sticking. Could be, but, as a newbie to propane, I checked that gauge almost every day and saw it drop incrementally. It took from December 2nd at 70% (move in day) to January 3rd to drop to 59%, and it was, as I said, quite incremental. It didn't just suddenly go from 64 to 61. In fact, you couldn't see the movement except over several days. And, it had not bottomed out and stayed at 59% for a week. Does that sound like a sticker?
For comparison purposes, this is in central North Carolina. Prices I was quoted for propane ranged from $2.249/gallon (price I paid at closing), $2.049 from the fluke who owned the tank, $1.999 from a competitor for "on call" if they "took over" the tank, $1.899 for autofill if they took over and $1.699 for autofill if I owned the tank.
So, does anybody know how a propane gauge operates, and am I the only person who thinks I should be able to use the delta percentages to derive approximate delivery gallons?
Oh, to add insult to the injury, not only does North Carolina have the highest motor fuel tax in the southeast, and one of the higher income tax structures, there is a 3% sales tax on electricity and natural gas, but fuel oil and propane buyers pay the full 7%. That's another rant, though.
Thanks for your replies
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Its a float gauge basically...
A long brass rod with a float on the end of it...as the level of liquid in the tank rises or falls the float rises or falls. At the gauge end of the float there is small gear which meshes with a larger gear on the part of the guage that mounts to the tank. They do stick occasionally.... what gets them is hauling the tnk to a new location with gas in it....there are no baffles in the tank and they will haul them with gas in them..forget the legal percentage that can be hauled ( think its 5 %) but I worked in prorane for a while years and years ago and we would haul them with 50 percent or more...depending on the time of year, situation etc.... anyhow...like any mechanical joint they break and can get bound up or loose...depending on what kind of movement they see in the tank. Expensive to replace...got to pump out the propane then replace the gauge and then refill the tank...
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It uses a float that rises with the liquid in the tank. Because of the tank's rounded top, they're just a rough estimate of what's in the tank. Go by what the gas company's printed ticket says. Those truck meters are usually calibrated by your local Weights and Measures Dept. You don't want to get on their list of bitchy customers. If you're concerned with energy savings, make sure you have a 90+ furnace. As for taxes, NC has one of the lowest tobacco tax rates in the country, so they have to make up the difference some other place.

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Had propane once....never again. You can get a better deal if you contract for it, but it's still too damned expensive.

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Yep, oil's much cheaper.

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though.
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Boyle, Logic and Propane gauges do not belong in the same world, let alone sentence. The truck meters are very accurate and are checked and sealed by the state. Gauges on tanks are made by a kindergarden class at Disney World.

Yes, you are.

You do have the option of moving. What is your electric rate? We now pay .169 here in CT. According to this http://www.dom.com/customer/pdf/nc/sched01.pdf you are paying less than half that amount. I'd gladly pay your rate and tax.
As for motor fuel taxes, regular unleaded is running 2.46 to 2.51 in this area. You still have the edge there according to this: http://www.raleighgasprices.com /
Before your beer get diluted with your tears, look around at the rest of the world and see how well off you are.
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NE PA: Residential electric is $.089 KWH. Regular gas is $2.44 gallon. # 2 Fuel oil is $2.04 gallon.
(add rr between nc and com)> wrote in message

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wrote:

Excellent point. Pressure in a propane tank is a better indication of temperature than the amount of propane in the tank. If there is a drop of liquid in there the pressure will be about the same as a full tank. In other gasses, sold in liquid form, they weigh the tanks. (CO2, N2O etc). That is also how you buy propane at the places that fill 20 POUND tanks.
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On Sun, 22 Jan 2006 12:40:44 GMT, Jim Murphy wrote:

Would NEVER rent a tank myself. Not having the option of going with the lowest price is not what I call a good idea - particularly since the folks I bought the tank from have consistently had the highest price for gas over the last 8 years). I use gas for heat only and fill up in August (so far haven't run out in winter - dual fuel) when the prices are the lowest of the year (at least in this area).
Since I only use gas in winter, it doesn't make sense for me to sign up for the "keep full" program offered by all the companies in the area, so I can't speak to the prices offered with those plans. I call around to all of the local gas companies the second week of August and get their prices, then I order from the company with the lowest price.
BTW, I was told by the truck operator of more than one company that the tank shouldn't be filled over 80%, particularly in summer, as the warmer weather causes the gas to expand and some of the gas will be forced out of the pressure relief valve. They said that underground tanks are less susceptible to this, but still don't recommend filling over 80%.

Been tracking levels in my 500 gallon tank, using the gauge, since Jan 98 (when we moved in - new house) and I've always managed to come up with a similar number to what was delivered, plus or minus a few gallons. I use 10%P gallons in my calculations. I check and record what shows on the gauge on the first of the month, year round to make sure that there are no leaks and to give me the information I'll need to figure out how much to order if I ever do run out in winter - don't want to buy more than I have to at winter rates.
Never had to deal with a sticking gauge so I dunno the symptoms, but, what's on the ticket is what you got. Here in GA, the meters on the trucks are regulated by the state just like the pumps at the gas station and are certified accurate. I'm sure that the same holds true in NC.
Later, Mike (substitute strickland in the obvious location to reply directly) ----------------------------------- snipped-for-privacy@bellsouth.net
Please send all email as text - HTML is too hard to decipher as text.
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