Propane Tank Capacity

[Jaytalk]

My rig has a 56 pound propane tank with a listed total tank capacity of 13.2 gallons. When the tank is full, how many gallons of propane does the tank actually contain? I know according to the tank gauge, when the tank is 3/4 full no more propane goes into the tank. So again my question is how many gallons is “actually” in the tank when it’s full?

[RogerR]

From my personal experience portable tanks are rated at their safe max fill. For example, a 20 pound tank will hold 20 pounds when filled to the safe maximum. There is some space for temperature expansion.

Larger tanks for permanent installation are rated in gallons. For example a 500 gallon tank. But they are safe to be filled to about 80 to 85% max.

A gallon of LP is 4.2 pounds at about 70 degrees. Propane expands and contracts quite a bit.
Note that exchange tanks at places like Walmart, CVS, etc. are filled only to 15 or 17.5 pounds even though rated to hold 20 pounds ( just a little rip off)

[Rustynuts]

Permanent mounted ASME RV propane tanks are regulated to only fill to 80% capacity to allow for expansion.

[EA37TS]

Originally Posted by Rustynuts

Permanent mounted ASME RV propane tanks are regulated to only fill to 80% capacity to allow for expansion.

I have a 500 gallon tank at the house to use for cooking, grill, fireplaces tankless hot water and whole house generator. It can only be filled to 80 percent or 400 gallons. All my motorhomes registered full when the tank was at 80 percent of capacity.

[EA37TS]

Originally Posted by Jaytalk

My rig has a 56 pound propane tank with a listed total tank capacity of 13.2 gallons. When the tank is full, how many gallons of propane does the tank actually contain? I know according to the tank gauge, when the tank is 3/4 full no more propane goes into the tank. So again my question is how many gallons is “actually” in the tank when it’s full?

56 / 4.25 = 13.17 pounds to gallons of LPG (LPG weight 4.25 pounds per gallon)

13.17 * .80 = 10.56 gallons when the tank is considered full.

[JimD]

I have the same size tank and tend to top it off when it gets down to about 1/2.

I recently installed the SeeLevel gauge system including the propane sending unit. My last 5 day trip to the desert at Thanksgiving dropped the level from full to 48%.

2 hours ago I went and had my tank filled. It took 6.6 gallons. So if the sending unit is accurate my tank would hold about 13.2 gallons. Granted, this is the ideal situation assuming the sending unit/gauge is accurate and I can suck 100% out of the tank.

[Jaytalk]

Originally Posted by JimD

I have the same size tank and tend to top it off when it gets down to about 1/2.

I recently installed the SeeLevel gauge system including the propane sending unit. My last 5 day trip to the desert at Thanksgiving dropped the level from full to 48%.

2 hours ago I went and had my tank filled. It took 6.6 gallons. So if the sending unit is accurate my tank would hold about 13.2 gallons. Granted, this is the ideal situation assuming the sending unit/gauge is accurate and I can suck 100% out of the tank.

Thanks for the reply. Are you taking into account the 80% of capacity issue the the previous person spoke about? If you used the 80% factor, it would seem like the maximum capacity would be around 10.56 gallons. What do you think?

[Jaytalk]

Originally Posted by EA37TS

56 / 4.25 = 13.17 pounds to gallons of LPG (LPG weight 4.25 pounds per gallon)

13.17 * .80 = 10.56 gallons when the tank is considered full.

Just filled up the tank with 9.5 gallons. Prior to fill up, the indicator gauge was below 1/4 and above 1/8. To what would you attribute the variance?

[JimD]

I think you have to take the gauge readings with a grain of salt. No telling how accurate they are. The only true way of knowing how much a tank holds is to run it empty. I would not want to take mine down below 1/4 while camping. I would be constantly watching the gauge and sweating it.

I recommend just keep it topped off when you are going on an extended trip of more than just a few days. You will eventually get a feel for how much propane you typically use. As long as you never run out, all is good.

I feel the 80% capacity rule is probably good. What really needs to be done is for manufacturers to start listing the true capacity of the tank. They still use the old measurements that may have been accurate before the advent of the fill limiter.

[Rustynuts]

What was nice when I installed my SeeLevel gauges it that after you are done with the install I went and topped off the propane tanks and then recalibrated the propane button on the panel to 100%. Seems pretty accurate now as when I filled up at 50% before a trip it took 5.4 gallons.

[JimD]

I absolutely love my SeeLevel gauge setup. I added a second gauge in the water fill area which makes adding water a bit easier. Only hooked up the propane monitor to the inside gauge. Definitely worth adding the propane monitor.

[pconroy]

11 ish.

[KoreanCowboy57]

80% is the most that you'll be able to fill any LP tank. Of course, that depends on the outside temperature. If it is hot outside the tank will fill more and might vent out some excess. But generally figure 80%

[saarf]

Spec sheet for my MH says tank is 16.5 gal/56lbs. Just recently gauge was on E and had fill up and took 11.1 gal to get to 3/4.

[salsa]

The best and cheapest way to find the level of a LP tank is to pour hot water over the side of a cold tank, like in the morning. Then run your hand down the side of the tank. When you feel the temperature of the tank change from hot to cold that line is the level of the LP in the tank.

[Jaytalk]

Originally Posted by saarf

Spec sheet for my MH says tank is 16.5 gal/56lbs. Just recently gauge was on E and had fill up and took 11.1 gal to get to 3/4.

What’s the year make and model of the motorhome you own?

[jrclen]

My gas man explained that the 80% leaves room at the top of the tank for the liquid to vaporize into a gas.