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Old 05-24-2010, 01:49 PM  
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Default Buyer beware - under-filled propane tanks!

It's no secret both Lowes and Home Depot get their propane tanks supplied by Blue Rhino and Amerigas. Well, these two companies only fill their tanks to 15.0 lbs., or about 3/4 only! Not only is that a rip-off, it is forcing people to change-out their tanks more frequently causing more gas driving to and from the store. I recommend getting a Grill Gauge ( and use it to verify your tanks are correctly filled to the maximum DOT allowable levels!!!

Chris S.

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Old 05-24-2010, 02:52 PM  
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It's my understanding that they only fill them so far to account for pressure expansion.
Have your tank purged upon refill to get the maximum. Go with refilling versus swaping to avoid any issues.

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Old 05-24-2010, 02:54 PM  
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What pressure are they supposed to filled to? It seems like leaving room for expansion of gasses might be a good idea.
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Old 05-25-2010, 07:19 AM  
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Default Propane tank weight

It's not about pressure, it's about 'weight'. A legally-filled tank should weigh out between 38 and 40 total pounds which includes the tare weight of the tank. I found out the Grill Gauge is calibrated for this as well and therefore is the most reliable way to measure propane in a tank...
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Old 05-25-2010, 09:32 AM  
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The tare weight is stamped on the tank (TW xx), just weigh the tank and subtract the tare weight and you have the amount that is in the tank
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Old 05-29-2010, 08:52 PM  
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You make a good point, but for the accuracy needed, why would you want to spend money on one of these:

if you could use one of these:

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Old 08-02-2011, 11:38 AM  
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This under-filling is not an error on the part of Blue Rhino or other suppliers. It is a deliberate under-fill while charging you the same price they did when they supplied a full tank. Use these from the grocery store, Lowes, HD etc only on Sunday afternoon when you run out and no filling station is open. Otherwise, use a propane filling station and you get a full tank for less than the cost of Blue Rhino or others. You can take the labeled tank in to a filling station and get it filled. The tank belongs to you once you take it out of the cage at the store.

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Old 04-02-2014, 02:47 PM  
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wrong info

Last edited by ryder7140; 04-02-2014 at 03:21 PM. Reason: wrong info
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Old 04-02-2014, 03:02 PM  
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The NFPA "National Fire Protection Association" has rules for filling propane tanks. There are 2 types of propane tanks. Tanks that are designed to be transported on highways are DOT tanks. That is what we use on our Barbeque grills. Tanks that are designed to be used in a stationary applications like a tank at your house for heating may be a ASME tank. DOT tanks must be filled by weight. You may have noticed scales at all propane dispensing stations located at hardware stores or RV campgrounds.

All DOT tanks must be filled by weight. It is the only save way to fill a tank. The tare (empty) weight is stamped on the tank by the manufacturer when the tank is made.

Propane weights 4.2 pounds per gallon. Most grill tanks are referred to as 20 pound cylinders, because they hold 20 pounds of propane. If the TW of a tank is 18 pounds and you add 20 pounds of propane, the total weight of the full tank would be 38 pounds.

If the tank is on the scale the operator would stop filling the tank when the scale reads 38 pounds.

You can check this by looking at the propane meter. If the person filling the tank has zeroed the meter before he begins filling it will read the total gallons delivered to the tank.

20 pounds of propane divided by the weight of a single gallon of propane (4.2 gallons) would be 4.7 gallons.

A full 20 lb. cylinder used for barbeque grills should hold 4.7 gallons and have a total weight of 20lbs. plus the empty weight of the tank.

If you see someone filling a tank on a scale and not watching the scale he should be reported.

Using a bathroom scale to get the total weight your tank before you connect it will tell you if the tank is full. A bathroom scale is NOT a certified scale but it can give you an idea if you are getting cheated.

All small DOT portable tanks now a days have OPD valves (overfill prevention devices). These valves are designed to prevent a cylinder from being overfilled. The OPD valves protects you from people who do not use the scales when filling a cylinder. The OPD valve has a float inside the tank and should stop the filling procedure when the tank level reaches 80% full. ALL PROPANE tanks are only filled to 80% volume. This is because propane is very sensitive to temperature. There must be space in the tank for propane to expand as the temperature rises.

This causes confusion because a propane tank is never completely filled. But all this is taken into consideration by the tank manufacturer when the tank is designed and manufactured. A full 20 pound barbeque propane tank should have abut 4.7 gallons and have a combined weight of the tank empty weight plus the 20 pounds of propane when filled to 80% of its volume.

I just purchased a 20 lb. cylinder from a CVS Pharmacy which sells propane tanks filled by Amerigas. According to my scales the tank was 4 pounds light. That is almost a gallon. Can you imagine the savings Amerigas is making by short filling tanks? Do a little count of propane tanks in the display cases next time you are driving around. This should be criminal.
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Old 04-02-2014, 04:45 PM  
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Boxes of books weighed on a postal scale should let you calibrate your analog bathroom scale. You can graph how your indicated weights differ from the postal scale weights.

For smaller weights I trust supermarket scales more than postal scales.

My digital scale shows to within 0.2 lbs but the maker is silent on the issue of accuracy except to say it's not for commercial use. It was right on for 44.00 lbs.

Asking about accuracy and alleging cheating is bad for business!

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