I recently had a second 80 gallon propane tank installed so that I would have extended run time for my 9Kw whole house generator.
The second tank is connected to the first tank and to my generator, and the first tank has a line that runs into my home for a gas fireplace.
The first tank's gauge currently reads 70 gallons, but the second tank is sitting at around 10 gallons. I realize that propane is a liquid in the tank, but as a load is placed on the tank, the liquid turns into a gas and it's this gas at the top of the tank that exits the tank and is used by whatever is generating the load.
So my questions are:
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Should I ever expect the tanks to equalize on their gauges? I expect the answer is no, as only the gas will readily transfer between the tanks.
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Can I infer the overall quantity of propane left in both tanks by reading the gauge on just one tank? I ask this, because the new tank has a gauge compatible with automatic tank level reading devices, and I'd love to add this to my setup.
Best Answer
Sounds like the two tanks are connected at the top (above the liquid line) since you say 'only the gas will readily transfer between the tanks'.
In this case, nothing equalizes the liquid level. Imagine if you run the two tanks down pretty far, and then only refill one of them; you can't see how much total propane you have available by only looking at one gauge.
Here's a random idea: you could put a valve between the two tanks, and fill them both, then close that valve. Treat one tank as the primary (probably the one that allows automatic monitoring), and the other tank is your 'reserve' (you have to monitor that level manually, but it will change less often). It's not great to have to manually engage backup propane, but it lets you get the most usage out of that automatic monitoring.
Update: What happens if a cylinder filled with propane gas is connected to an empty one of the same size