If my regular propane tank for the house runs out can I use a BBQ tank as a temporary fix? What will I need to do this?
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A BBQ tank isn't that much propane in the grand scheme of things...– ThreePhaseEelJan 31, 2015 at 1:52
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2I just did this at home, and had a shower (the highest use device in my house) it works fine and saved me from a week of cold showers.– Chris PugmireAug 10, 2017 at 20:51
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1It depends on what inside your house runs off of propane. If it's just your hot water heater and oven, then yes that'll be fine. If you want to run your furnace, then that's probably too much for it to make sense.– DotesDec 11, 2017 at 17:50
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1We did this last month to keep my sister in laws house from freezing after she passed. We turned the temp down on the thermostat and used a 15 gallon tank not sure how many days it lasted but there were no frozen pipes the following weekend but the tank was empty on Saturday so less than a week on 15 gallons in low 20 temps put another tank on and the next week got a delivery for the main tank so it might help I am sure it kept the pipes from freezing.– Ed BealFeb 17, 2019 at 2:00
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Once again, location is an important factor, of which we are deprived. Why can't questioners understand how important this information is, and include it in the question?– TimMar 31 at 19:46
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2 Answers
This generally won't work all that well. While both large and small tanks contain propane, the large tank can deliver more propane to appliances than the small one can.
Propane is supplied as a liquid under pressure. The pressure in a propane tank is pretty much an indication of its temperature, not the amount of propane in it. When propane is drawn off by an appliance, the propane in the tank boils to make more gas - and that boiling lowers the temperature of the tank. A small tank, especially a small tank in winter, can become so cold that it cannot effectively supply gas.
This PDF (which unfortunately lacks page numbers to refer to) lists vaporization rates for various sized containers (100 lbs being the smallest, 5 times your typical BBQ cylinder) at different temperatures on the 6th page - at 40F the 100 lb can deliver 61,500 BTU/hr, at 20 F 43,300, and at 0F 25,000 - A pound of propane is 21,600 BTU, a gallon is 91,000 BTU.
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I wonder if BBQ tanks actually contain propane. Used mainly in Summer, they're likely to hold butane, which hardly gases at 0 degrees C. Propane itself is good for much lower temps. I've used small propane tanks for cooking and showers in below freezing temps with no problems. The pressure I used was something like 35millibars, which is hardly a whisper by the time it comes out of the regulator. Such as would be used in a caravan.– TimMar 31 at 16:39
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1It would be Very Illegal to fill a Propane cylinder with Butane. While Butane is common "bottled gas" in some areas, and Propane is in others, they are by no means the same, they don't burn the same, and it would violate a bunch of regulations to fill a tank labeled for one with the other.– EcnerwalMar 31 at 16:55
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I'm not saying fill a tank with the 'wrong' gas. Just saying (and I do it often) either will work with lpg appliances - with the appropriate regulators, it's just that propane has a much lower boiling point than butane - and in any case, I believe, depending on the time of year (and possibly location) mostly lpg is a mix of both, rather than pure butane or pure propane.– TimMar 31 at 19:09
It's possible in an emergency but it will not last long. Making the connection is somewhat difficult if you don't have the parts. The regulators are different threads. Tanks use national pipe thread after the regulator and cylinders (bbq tanks) use cylinder threads (M something or whatever).
How much propane you can get out of the cylinder depends on how cold it is outside and how fast it is being drawn off. If you managed to get it connected you could place the cylinder in a warm water bath after it cools. You could even connect inside directly to the furnace but you will still face the cooling issue. Also, propane mishandled is EXTREMELY DANGEROUS. Do not attempt any suggestions from anyone unless you are experienced with hydrocarbons. 1lb of propane contains about 20,000 btus so a 30lb cylinder on an 80,000 furnace theoretically should last about 7 and a half hours. You'll have to fight to keep it warm the whole time.
Seriously don't attempt anything that you are not comfortable with. It may even be illegal to bring a cylinder inside. If you are comfortable with it and want a satisfactory result, connect 4 or 5 cylinders together and the freezing problems disappear. We do that often on construction sites.
