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At my house, the previous owner was a huge fan of propane. I've got gas lines running to the main floor fireplace, a basement fireplace, kitchen and the deck. All I ever use and have hooked up is the main floor fireplace, and even that only during winter time.

The previous guy had a massive 500 gallon tank in the back, since I have no use for that much and I wanted to avoid renting it, I opted out for a smaller, 100 pounder.

The problem is, the 100 pound tank doesn't work, it feels like there are so many pipes around the house, even with the taps closed at the edges, there isn't enough pressure and I need a larger tank just for the sake of getting the pressure to power a single small fireplace.

Another supplier said that because of the freezing winter temperatures, 100lb tanks aren't usable and I need at least 420lb because in the smaller tank, in cold weather, the propane wouldn't vapourize, so while 100lb is enough to provide the pressure, it wouldn't work anyhow.

Since I've run into some not-quite-honest providers around here before, I'd love some real input on what to do here.

My plan right now is to simply disconnect all the gas pipes at the source and install a new pipe only for the fireplace I want to use, and stay with the 100lb tank.

Any ideas and solutions are of course welcome

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  • What is the BTU/Hr rating of the fireplace burner?
    – Ecnerwal
    Oct 7, 2020 at 20:50
  • a tank warmer may be a solution so long as the weather doesn't get cold enough for the gas to start condensing in the lines. (about 40 below)
    – Jasen
    Oct 7, 2020 at 22:57
  • 22k low to 29k high btu/hr. Outside temp can drop to -25c
    – dyasny
    Oct 7, 2020 at 23:09

2 Answers 2

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Propane is stored and shipped as a liquid under pressure. That makes it convenient to store and ship a usable amount without needing very high pressures.

The pressure in a propane tank is a function of temperature.

When you use propane, the liquified gas in the tank boils. As it boils, it takes the heat needed to vaporize the liquid (latent heat of vaporization, from chemistry class) from the air around the tank. In summertime it's not uncommon to see frost forming on a 20lb tank attached to a barbecue grill.

So, the pressure in the tank drops as the liquid in the tank cools, until it can get more heat from the air.

Thus, when you want to use a fireplace (it's cold out) that happens ot be the worst time to place a heavy draw on a small tank. The tank gets cold, the pressure drops until it cannot supply the pressure required, it gives up.

Your disused connections, if not leaking, have no effect whatever on this.

Your best bet if you don't like renting a tank is to purchase a tank, and the best bet for that is to have it (correctly and to code) buried, where it will be warmer than it would sitting out in the air during winter weather.

Otherwise, you need to have a large enough tank that the rate of gas use does not overcome the ability of that size tank to supply gas at a particular outdoor temperature. Even with a buried tank, the rate of gas use must not be too great for the size of the tank, or it will still self-chill and fail to provide adequate pressure.

You can also manifold multiple smaller tanks (so if you are really dedicated to 100 lb tanks, you could gang 4 or 5 of them together rather than have a 420 lb single tank, if your local supplier, who does not appear to be dishonest, is estimating correctly for your local conditions.)

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  • A buried tank will probably not be an option, but 420lb is something I can definitely afford. Thanks for clarifying this, I usually tend to trust people but two different providers giving two different answers gets my scam radar going
    – dyasny
    Oct 7, 2020 at 23:34
  • I'd only add that the boiling point of propane is -40F, so if the propane gets below this temperature, it won't boil,which is what I expect is happening in cold weather. With frost forming on a tank in the summer, that's easily a 40 degree drop, so zero or sub-zero temperatures sound like they could create this problem. I'd imagine another alternative would be just a simple heat wrap around the cylinder, hooked up to some kind of thermostat. I'd make a guess someone sells this.
    – user30371
    Oct 8, 2020 at 0:56
  • @SteveSether the previous owner had a large propane tank working here, no extra heating, nothing. Just standing outside.
    – dyasny
    Oct 8, 2020 at 18:38
  • A larger tank is going to have a larger surface area to absorb heat from the environment, and a larger amount of propane to cool down, so of course eventually the surface area is going to be large enough to heat the propane enough to boil at sub-zero temps. I'm just saying it's possible you could get away with a smaller tank+heating.
    – user30371
    Oct 9, 2020 at 1:31
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I do not know how much propane you plan to use or the total btu's of the appliances you will ultimately connect to the tank but I can tell you what my wife and I used in our old house. My wife always cooked with nat gas and did not want to try electric cooking so when we moved into our last house I hooked up and converted her nat gas stove to propane. You could use the oven and all 4 top burners at the same time. We were in that house for 20+ years and the propane worked as her cooking fuel with no problems. Our hook up consisted of 2-- 100# tanks with an auto switch over so when 1 tank emptied the other was put into service. The propane worked great.

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