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I once wrote a post entitled “How do you know that it’s full?” It talked about the weight of a propane tank when it is filled to capacity, good info to have when you’re paying for a full tank but not sure that you’re actually receiving it. Read that post… been there — done that! In hindsight, it seems that perhaps I should have used my own info yesterday to determine if our tanks were near empty!

Rebecca and I had become aware that the primary 20 lb. propane tank that fuels our boat’s cooking system was near empty. We could tell this because the fancy gauge on it, which experience has shown us to be fairly accurate, was flatlining in the red section. Yesterday, after having cleaned everything out of the locker where the tanks reside, I thought I would be smart (efficient) and remove the main tank and switch the system over to our 10 lb. backup cylinder even though I knew that I couldn’t get the other tank filled until next Friday.

As cruisers here do, we dropped the tank off at the guard gate at one of the boat yards and prepaid to have it filled. Apparently someone will come around and pick up the tanks next Friday and return them to the same spot on the Saturday after topping them up.

We returned to our boat, had a nice dinner later in the evening and even managed to half boil some water this morning for coffee. You guessed it… that it when the second tank, which we assumed still had a fair amount of propane in it, ran out. Without a gauge like the larger tank has, I was really just guessing about how full it was. Of course, if I had known its weight when empty, which I didn’t at the time, I could have weighed it to get some idea of its contents. Would I have done that, down in the bottom of the locker yesterday? I doubt it. Would I do it now, after this fiasco? Absolutely.

Unless we sort something else out, we now have a week to go without propane to cook with. Our friends on s/v Joana have already offered to lend us one of the small green cylinders which can fuel our barbecue grill so that will look after us for today. I know that I can get the larger tanks filled in Port of Spain tomorrow while Rebecca is at school (today is Sunday and the place that fills them is closed). I’ll just have to figure out transportation to get them there as I know that I won’t be permitted to take the propane tanks on the public buses. Fun, fun, fun!

Note: The water in the kettle was just warm enough to make coffee this morning. That disaster was narrowly avoided!


  1. All propane tanks have the empty weight of the tank stamped into the collar of the tank. You can also buy a small multi-fuel single burner camp stove for emergency use. Boy has the price of these things gone through the roof. A friend bought one in the 80s for $30 now they are $130. He bought the dragonfly and loved it.

  2. Mike can’t you also make an adaptor hose to use the small green cylinder (your friends offered) to connect your stove in the boat? You may be able to connect it right where your existing propane is normally hooked up, or at the stove location. You could then buy one or tow of these to have as backup tanks.

    You could also just buy a small one burner camping stove as back up. Not having morning coffee can become a huge problem I’m sure.

    I have a feeling as resourceful as you are you have already thought of this.

  3. This is the biggest reason I am trying to convince Mark we need composite tanks- being able to SEE how much fuel you have without a sure to fail gauge.

    • The reason we chose to use a steel tank for the primary was the thought that we might be forced to “swap” the tanks at some point in our travels. Obviously we wouldn’t want to leave a nice composite or aluminum tank behind. As it turns out, that has never been the case. We do frequently have to leave our tanks some place and collect them at some point later after they have been filled but we have never had to trade them in.

  4. Mike if you lift any LPG tank (with aa straight and extended arm) just a few inches off the floorsort of dangling it) and position your sholder directly over the tank so that you swing it once about six inches either way. then relax your arm(still holding the tank off the floor) any liquid gas (ie a couple of days gas) will cause a pendelum effect and you will feel the tank being moved by the sort of free surface effect of the remaining liguid gas. Hope this helps.

  5. So sorry about my grammer, and typing expertese.

  6. Mike –
    The pressure in a propane tank will be the vapor pressure of the propane at whatever the temperature is, as long as there is a single drop of liquid propane still left in the tank. The pressure gauge will not show you that you are low on propane until there is no liquid left in the tank at all – at which point you are not low on propane, you are essentially *OUT* of propane. Those pressure gauges don’t tell you very much of anything useful. Weight is the only reliable measure of the contents of the tank – or as a previous commenter suggested, get one of the new fiberglass tanks where you can actually see the liquid level. But I wonder how the fiberglass tanks stand up to UV…

    s/v Eolian

    • I’m not sure that it’s measuring the pressure then because the needle on the gauge goes down uniformly as we use up the propane.

      Our propane tanks are stored in a locker so UV would not be an issue for us. I have seen several boats that have them stored on the rail though. That is good for seeing the propane level but as you said, much more exposed to the sun and the elements.

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