Mh propane capacity discrepency

My propane tank has a bleeder screw that the propane attendant opens when they fill the tank. It is located about 3/4 of the way up the tank on the front. It is at the 80 percent mark. When the propane reaches the bleeder valve, the propane will start to come out. At this point, the attendant closes the valve, and stops pumping propane. Since they are pumping liquid propane in, the valve allows air to be displaced by the liquid coming in. Im no expert, but I don't think ever tank has this same valve. I don't think my friends rv has one, but mine does. The reason you only fill the tank to 80 percent is that in hot conditions, the propane will expand. The 20 percent is a safety margin to allow for safe expansion.

down home wrote:
Our 05 Revolution has a 38.4 gallon propane tank. The factory replaced the original tank circa 2008.
We let the tank run down to an indicated empty lat night.
Filled it this am but it would only take 24 gallons.

A full fill for a 38.4 gallon tank is about 27 gallons (34.8*80%) I'd say your 24 is very very close just a bit off on the float valve .

I doubt the gauges on the tank are precise. E may not be Empty. If you really want to know how much it actually holds, run it empty.

There is no mechanical linkage between the float and the gauge. It's done with magnets. There's a lot of slop there. Don't expect to achieve a lot of repeatability. It's only designed to give you a rough estimate of the level of liquid propane left in your tank. When filled to 80%, your tank is full and you shouldn't put any more than that in it. If the gauge was completely mechanical, it would be venerable to leaking and that can't be tolerated because of the nature of propane.

Tank capacities are shown in gallons of water, theres a plate on the tank that shows that. Propane capacity is 80% of the water capacity (WC) #. A 38 gallon tank would hold 30.4 gal of propane. Never seen one that big.
Since you post you are taking on about 24 ga. , that is in the range of a 100# tank with a WC of 28. Check your numbers. That is a common size.
There is no air or water in a propane tank. The bleeder screw is a mechanical full level dip tube that will bleed liquid propane at the 80% level, vapor at lower levels. The guage on the tank is a mechanical float guage, that sends a signal to the in coach guage. Trust the on tank guage.
Also consider that if 80% is full, the 1/4, 1/2, 3/4 (full) should more properly read 1/3, 2/3 3/3 Full.