What does 1/2 reading on LP Gauge mean

[chiliman]

I understand my 28 gal lp tank can only be filled to 80% (22.4 gal).

So when I read the guage on the tank and it indicates 1/2 (approximately) does that mean 1/2 of 22.4 or 1/2 of 28?

Thanks

[mdprince]

Louseman wrote:
Here is a great webpage that explains the components of an RV mounted
propane tank:

RV Tank Innards

Seeing what is inside, can help you to determine what you are seeing
outside, and how to judge the gauges.

Thanks for posting. Very cool to see !!

[xctraveler]

Kayteg1 wrote:
I don't see how the Innard page helps in this topic.
Gauge calibration is just that >>> calibration. You can scale it any way you want.
I have not seen a gauge that would show 80% on tank filled up to capacity. If such thing exist, it was design by idiot.
No offence.

Sorry Keyteg, I have had three coaches with ASME horizontal tanks. On each the gauge ON THE TANK showed/shows 3/4 (approx) when the tank is full and liquid propane is coming out the tank full vent. The idiot lights IN the coach read Full at that point. I have little faith in the on board lights so as soon as it shows less than full I duck outside to verify with the direct read gauge on the tank.

Most other coaches I have looked at seem to have the same set up.

Must be that all the people involved in designing these systems are idiots if you are correct.

[Mont_G_J]

28 gal = 100%
14 gal = 50% or !/2 on gauge

[Kayteg1]

I don't see how the Innard page helps in this topic.
Gauge calibration is just that >>> calibration. You can scale it any way you want.
I have not seen a gauge that would show 80% on tank filled up to capacity. If such thing exist, it was design by idiot.
No offence.

[Tinstar]

That RV Tank Innards page is good information.

If you want to know exactly how much is left, go have it filled when the gauge shows 1/2 and see how much it takes to reach full.

[Louseman]

Here is a great webpage that explains the components of an RV mounted
propane tank:

RV Tank Innards

Seeing what is inside, can help you to determine what you are seeing
outside, and how to judge the gauges.

[Dutch_12078]

Kayteg1 wrote:

SDcampowneroperator wrote:
If 75- 80% is full, then when your float gauge shows 3/4, thats full. So. 1/4 on the guage is actually 1/3, 1/2, is 2/3, 3/4, is full.
Your DOT tank capacity is stamped on its welded on plate. Look at it, do the math, know your tank size. .

First time for me to learn that propane distribution is regulated by Department of Transportation.
When I believe there is lot of variations in propane tanks, those that I use for decades on forklifts and residential are marked F-1/2-1/4-E
Would what you are saying apply to them, they would never show "F" when in fact they do each time I fill them up.
Forklift tanks and residential are still exempt and they don't have float fill valves.

The portable LP cylinders typically used on towable RV's, gas grills, etc., must meet the specifications established by the USDOT. The permanently installed LP tanks typically used on motorized RV's meet the specifications established by the ASME. The OPD is not a DOT or ASME requirement, but it is a requirement of NFPA 58, the standard adopted by most/all states in their fire codes.

[Kayteg1]

SDcampowneroperator wrote:
If 75- 80% is full, then when your float gauge shows 3/4, thats full. So. 1/4 on the guage is actually 1/3, 1/2, is 2/3, 3/4, is full.
Your DOT tank capacity is stamped on its welded on plate. Look at it, do the math, know your tank size. .

First time for me to learn that propane distribution is regulated by Department of Transportation.
When I believe there is lot of variations in propane tanks, those that I use for decades on forklifts and residential are marked F-1/2-1/4-E
Would what you are saying apply to them, they would never show "F" when in fact they do each time I fill them up.
Forklift tanks and residential are still exempt and they don't have float fill valves.

[pianotuna]

Hi,

Not on my RV with a mechanical float gauge. The 80% is marked and 1/2 is marked.

IAMICHABOD wrote:
As explained to me by my propane guy,it is 1/2 of the 80%,regardless of size.

[SDcampowneroper]

If 75- 80% is full, then when your float gauge shows 3/4, thats full. So. 1/4 on the guage is actually 1/3, 1/2, is 2/3, 3/4, is full.
Your DOT tank capacity is stamped on its welded on plate. Look at it, do the math, know your tank size.
The capacity expressed in gallons on that plate is its total capacity of gallons(or liters) of water, maximum LPG capacity would be 80% of that water capacity.
This is the most misunderstood topic we deal with at our propane dispensing station. Because of the misunderstanding of readings, many, too many think they are low on propane, because they see a 1/4 reading when actually they have 1/3 or more of tank capacity.
Edit, I meant asme tanks instead of dot. Thanks for the correction.
Asme tanks are mounted tanks on vehicles and stationary for other uses. Dot 'bottles' are portable, in most cases do not have level guages.
Permanently mounted tanks that have float level guages that read as full @ 80% are the effort of my post, to help the many inexperienced understand that the levels they read on it are actually thirds of capacity, not quarters.
Max

[gbopp]

Kayteg1 wrote:
For me running out of propane is easy to figure out.
IT ALWAYS happen Saturday night.

I think that's a federal law. You are not allowed to run out when it's convenient or readily available. 🙂

[Kayteg1]

For me running out of propane is easy to figure out.
IT ALWAYS happen Saturday night.

[CloudDriver]

DrewE wrote:
It depends somewhat on the gauge and the shape and mounting of the tank (for a float gauge). I don't think most of the ones on horizontal tanks are calibrated much to the changing geometry of the tank, for instance, so the middle quarters are bigger than the top and bottom quarters. I also think mine shows circa 80% after filling (so it's percent of water capacity), but I am not completely sure of that.

To me, 50% means I don't have to start thinking about buying propane yet.

X2 on the above.

Pretty sure the gauge on our horizontal tank is a float type gauge. It indicates about 80% full at maximum. Also there is an auto shutoff on the fill connection that prevents the tank from being filled past the 80% point. As Drew already indicated, these horizontal mounted tanks have most of the liquid volume at the wider portion around the halfway full point. Your 28 gallon tank contains about 14 gallons at the 1/2 full point. At the 1/4 full point it doesn't contain 7 gallons. More likely only 3 or 4 gallons. I forgot this fact one time and almost ran out of propane.

[Kayteg1]

The gauge should show the propane level, not the tank total capacity.
Same in cars and trucks, where you have air bubble for fuel expansion.
That said none of those gauges is too accurate so you might want to calibrate them.
The best way I figure out is take a look at propane tank on cold morning, where condensation sets on filled part.
They also make thermal tapes that can sense the actual level.
I wold advise to run the tank empty or very low from time to time.
Had it on older motorhome that was refilled too often and it accumulated heavy fractions at lower 1/2 of the tank.
When I start drawing that low, the water heater would smoke heavily putting sot on whole side.