Another propane question

3oaks wrote:
I don't think anyone gets 20 lbs of propane today. The mandated opd valves take up some of the tank's volume.

It's also been many years since I had anyone fill my propane tanks by weight. The suppliers I have used at home and away from home all use the little bleed valve to know when the tank is full to it's safe capacity.

20# IS 80% of cylinders full capacity (or 30#, 40# etc)

OPD is set for 80%
Bleed screw (liquid tube is set at 80% level
Weight is measured for 80%

best place to fill is costco, flat rate $7.99 a fill in Calgary Alberta and $9.99 Ontario, most places up here charge $20.00 to fill, most are rip offs at $20

Old-Biscuit wrote:

20# IS 80 percent of cylinders full capacity (or 30#, 40# etc)

Why do people insist on this? It is not true.

20# is the 100 percent capacity of a 20# cylinder. A 20# cylinder only holds 5 gallons of liquid, filled to the neck. 5 gallons of liquid propane weighs 20#. How can it otherwise? It is the same height and diameter as the ubiquitous "5 gallon bucket," which is also filled to the rim when it contains 5 gallons of liquid.

Like anything else, the manufacturers use whatever they can to make their product sound bigger, better, more capable than it really is. Vacuum cleaners with "13 Amp" motors, for example. Yeah, 13 Amps is the current when the motor is STALLED, i.e. not "sucking." So, really, a lie. Cargo capacity of a car/truck/van in cubic feet is another little white lie, because it includes every useless nook and cranny in the vehicle. 100 Watts per channel on your stereo. If you push 100 Watts through each channel, the sound is so distorted you can't understand what Rush Limbaugh is saying!

If a 20# propane tank could really hold 25# of propane filled to the brim, you can rest assured manufactures would have called it a 25# tank from the get-go.

mkirsch wrote:

Old-Biscuit wrote:

20# IS 80 percent of cylinders full capacity (or 30#, 40# etc)

Why do people insist on this? It is not true.

20# is the 100 percent capacity of a 20# cylinder. A 20# cylinder only holds 5 gallons of liquid, filled to the neck. 5 gallons of liquid propane weighs 20#. How can it otherwise? It is the same height and diameter as the ubiquitous "5 gallon bucket," which is also filled to the rim when it contains 5 gallons of liquid.

Like anything else, the manufacturers use whatever they can to make their product sound bigger, better, more capable than it really is. Vacuum cleaners with "13 Amp" motors, for example. Yeah, 13 Amps is the current when the motor is STALLED, i.e. not "sucking." So, really, a lie. Cargo capacity of a car/truck/van in cubic feet is another little white lie, because it includes every useless nook and cranny in the vehicle. 100 Watts per channel on your stereo. If you push 100 Watts through each channel, the sound is so distorted you can't understand what Rush Limbaugh is saying!

If a 20# propane tank could really hold 25# of propane filled to the brim, you can rest assured manufactures would have called it a 25# tank from the get-go.

No they would NOT.......due to regulations and design cylinders MUST have a vapor area.
That area is needed so that liquid propane can 'vaporize'
'Vapor' is what comes out of service valve to be used/burned
Vapor area is required for RELIEF VALVE
Vapor Area is needed so that LIQUID propane does not come out of service valve----ruins regulators

Before OPDs.....cylinders got overfilled because PEOPLE screwed up filling them beyond the 80% which is where the end of liquid level tube is set---bleed screw (80%)

1 gallon of propane weighs 4.2 pounds. A "full" 20 lb cylinder should have 4.7 gallons or propane in it.
"FULL" is 80% of capacity


30# -------7.2 GALLONS (80%)
40#........9.5 GALLONS (80%)


READ for Propane Education




Semantics......
FULL 20# cylinder will hold 4.7 gallons of liquid propane
FULL is 80% capacity liquid level
FULL 20# cylinder will weight 38# (18# for empty cylinder weight PLUS 20# for weight of propane)