When is the propane tank "empty"

[reedbr]

When is the propane tank empty, based on the pressure gauge?  I think I have seen it up around 150psi in the past, yesterday it read 120psi.  At what pressure is it empty enough that it won't provide a good flame?  I'm trying to gauge when to refill it.  I used to fill once a season regardless, but according to the fill station it didn't take too much.  I use the stove frequently for cooking for a family of five and occasionally use the oven, so I'm surprised at how little I use.

[Footloose]

Brian,

As far as I know the gauge does not tell you that the cylinder is empty until it reads zero.  The different readings that you are getting is due to the different air temperatures.  The only reason for the gauge is to tell you if you have a leak.  Pressurize the system, turn off the gas, and see if the pressure drops after 15 minutes.

To tell if it is empty you have to weigh the cylinder.  Obviously you have to know what its empty weight is for this to be useful.  We still have the small cylinder and cook on the boat several times per week during our short season.  We fill it about once a year.  It doesn't take much gas to run the stove.

[Ken Juul]

Weight is the proper way to determine how much is left.  The weight of the tank should be stamped on the handle, you can get a fish scale and wiegh the tank monthly to detemine how much is left.  Or you can do the shake test, it will give you an estimate. 

I estimated my 11# was about half full last spring, used it all summer for coffee/breakfast and an occasional lunch/dinner.  Felt about 1/4 full when I shook it last weekend.  The stove really doesn't use that much gas.

[John Sheehan]

Another way to check the volume of the tank is to take the tank out and pour hot water over it.  Then you can feel the level by temperature.  It will stay hot above the level and be cooler below it.

We took a 6 week cruise on our 34 and then lived aboard for four months in the winter cooking every day and still had propane.  I have an adaptor that goes from the small propane tank we use for our Magma grill to the hose for the propane.  That way if we do run out we can still operate the stove until we can get to a place to refill the main unit.

John

[dpenz]

You can also buy a propane tank "gauge", a heat-sensitive magnetic tape that sticks onto the tank.  Pour hot water over this, and it clearly shows the level.

I also keep a spare 1-lb bottle on board with an adapter.  When my main tank runs out, every two or three years, I swap in the spare until I have an opportunity to refill.