if you refill it and get the same tank back, then you pay for only how much they put in. if you go to an exchange place, you pay for a full tank, whether you had half a tank in your or not. and some exchange tanks are not at the 80% full mark either(you can only fill a LP tank to 80% rated capacity), i have got them before that you could tell just by the fell that they had half a tank or so.

Thanks for the war stories, I think Agway in NJ does charge by the number of pounds they use to fill, making that much better than buying 20 pounds each time. I have learned (most?) tanks weigh 18 pounds, so full they should weigh 38 pounds. That said, if they are only 80% full, 16 pounds, because of the new safety fill valve the full tank will weigh only 34 pounds. I haven't purchased propane in a couple of years, suppose the price per pound must be at least double what it was back then, considering the general rise in energy cost. What's the going rate these days, $1 a pound? Hope less. This higher price makes it more important that one pays only for what the get.

I filled propane tanks at my former employer, and the new tanks are rated the same as the pre-OPD valve tanks were. You're not getting less gas now, a 20 lb. rated capacity tank holds the same amount it ever has. The "old" tanks were supposed to be filled to 80% capacity to allow for expansion. There just wasn't any built-in device to keep them from being overfilled. The new tanks are the same size.....they just prevent the filler from filling past the 80% mark. It was possible to overfill the old tanks, but doing so was silly. If a person put the tank in an enclosed area, (garage or car for instance), and the tank warmed up, then gas could escape from the relief valve.

The OPD valves were mandated to keep the tanks from being overfilled. 600 or so fires per year were attributed to gas escaping from overfilled tanks prior to the switch to OPDs.

Any idea how many gallons? A local Mobil sells propane, $10 for the 20 pounder. I have gotten anywhere from 2.5-4.0 gallons depending upon who fills it.

Google tells me 4.2 pounds per gallon (that must be at some standard temperature and pressure).

Some other info I found:
BTU/Gallon 91,520
BTU/Pound 21, 548 (I didn't check the divide by 4.2)
Current price $1.87 per gallon, says $8.90 for 20 pounds, but that's in large quantities, I think, so a price of $10+ sounds about right for 20 pounds.

It shouldn't matter who fills it....only how much was left in it when it was taken in to be topped off. We looked at the tare weight of the tank, (empty weight), and added 20 lbs. to whatever that figure was. The tank was set on a scale while being filled, and the sliding balance weight on the scale was set to whatever the tare weight + 20 lbs. figure was. (Usually 37 or 38 pounds.)

Didn't matter who was filling the tank....once the beam on the scale balanced, that was followed immediately by the OPD valve closing on its own and not allowing any more propane into the tank.

Keep in mind that that's the *short* way to do it. What's actually supposed to be done, is the WC rating, (water capacity), is looked at. There's usually a chart next to the filling station that shows different sized tanks on it. "20 pound" tanks are usually stamped with a WC of 47.1 pounds. The chart then shows what the propane capacity in pounds is, and that figure is combined with the tare weight in order to come up with a "weight when full" figure.

;-)

Why would you refill a tank that has propane still in it, especially on a gas grill? If it's so important have a spare tank fill. Propane prices vary throughout the year in winter price will be high in summer price will be lower due to less demand. I had mine filled up completely in my area empty 14 bucks to 17 bucks in summer, however winter prices approach 20 buck and more. Highest price I ever paid was 28.50. so it's wise to get it when the price is low. I wouldn't exchange unless I wanted to get rid of a old tank, you pay for somebody hauling it there and the store commission.

I haven't had a propane tank filled in a long time. But when I did, they did not seem to care how much gas was left in the tank when you brought it in for refill. They just put the tank on a scale and shut it off when it went to a certain weight. They did not even figure in the weight of the coupler and hose they had attached to the tank. I always paid the same amount no matter how much gas they put in the tank. They had a set price to fill a certain capacity tank, no matter how much of the old gas was left. Charles Ranheim

I went to a propane filling depot in Lebanon, Pa., to get my travel trailer bottles refilled. One was cpmpletely empty, the other only took a small amount. The man in charge tried to charge me for two complete re-fills! But, when i fingered my cap with the trucking company logo on it, and implied that the Company folks in town would certainly be interested in how he was ripping off the truckers and others, and the price he wanted suddenly came way down!

Well I have a tank I know is empty, I'll take it to my local Agway, and I'll ask, anyway, what I'm buying: "X" gallons or a one-price fits all fill.

Wrong, I weighted the "empty" tank and it came in a bit over 30 pounds, must have a good bit of gas left. I thought it was empty because the burner put out a low flame, would not go to high output. Suppose the burner head is dirty.

Actually, the mot common reason that a grill flame suddenly becomes low is that the regulator cut the flow down. They do this more commonly when you open the burner first and then the regulator. A regulator can decide to do this on its own if it thinks it detects a surge. Best way to handle this is to close the tank valve and burner valves and disconnect the hose from the tank for the regulator to reset . You can even tap the regulator against the tank to help it release if it sticks a bit. Hose on, tank valve open and then light the grill. Typically does the trick.
The regulator is adjustable as well if need be. Always a good idea clean the burners inside and out once in a while too. Spiders like to camp out in the tubes going to the burners too.

Thanks for the tips, it's raining today so I'll look later. I hadn't given any thought to the regulator, but I think I did open the burner head, then the tank valve, as I recall.

Is the regulator of which you speak that unit right at the attachment to the tank? Must be, I don't recall anything else in the line other than the burner volume control valves mounted on the control panel of the BBQ.

Yes- that's the regulator. Be over for grilled lobster later. . .

Scary! I attached a new tank to my outdoor grill. When I turned it on, it began to hiss and gave off the smell of propane. I immediately turned it off. What may be the cause? Defective tank? The previous tank worked OK until it quit. It didn't feel quite empty when I lifted it up -- but I'm not 100% sure. Any advice?