The Flexcon 62 ga pressure tank holds 62 ga I guess max when the bladder is fully extended...I think.....
If you cut the power and run the faucet dry...how many ga will be left in the tank??

 

The WR-200 is rated for 62 gallon capacity. At 20/40 pressure.... the drawdown is 25 gallons.

The chart at the website is very helpful.
Flexconind.com/pdf/wr_specs.pdf

 

A pressure tank is never completely full of water (at least when it's working properly). The drawdown or tidal volume PJmax provided is the number you are looking for. If the tank is completely full when the power goes out you've got about 25 gallons of water. Be warned that the water will flow normally all the way to the end and then it will just stop without much warning.

 

You should also understand that not only water is in your tank but also air. Without the air the tank will not provide any pressure. A pressure tank, when optimized, will produce around 25% to 30% of its size in usable water, before the pump kicks on to refill it again. This is just an estimate. PJ's chart will be more accurate.

 

so the 62 is just total capacity....once the 25 ga is gone the tank has no water in it.. or maybe a couple pints..??

 

62 gallons is the size of the container. Reading the tank specs for your water systems pressures tells you about how much water it holds when it's full. And, when the power is out and you leave the faucet on until the water stops flowing then the tank is empty.

 

If the pressure tank were nearly filled with water then the air cushion in the remaining tank space will run out of push power when perhaps three gallons came out of the pressure tank and the pump has to kick on again.

In typical operation given proper pre-pressurizing of the pressure tank the amount of water inside ranges from nearly none to about a third of the tank capacity as the pump cycles on and off.

The exact percentage of the tank capacity that can be occupied by the water depends on the pump start pressure relative to the pump stop pressure together with the tank pressure with no water in the tank..

 

I drain my tank when I leave the house for awhile.... so I want to have the least gallons
in it that I have to dump on the ground outside. Along with the 40 ga I dump from the hot water tank. Its a waste. If I had the time to design it I might have skipped buying a new pressure tank completely and maybe just filled a thirty gallon container container from the pump manually
and put a small cheap RV pump to push it around the house. Along with an on demand water heater it would waste less water and would have been much cheaper.

I replaced my pump with a new Franklin 1 HP ,110 ft of dropline, a new 62 ga pressure tank
and some plumbing for the tank. 2500$. At least 500$ more than it was worth.
But when your water goes out you want it fixed right now and you end up getting a bad deal.

 

If you are concerned about the amount of water that may be in the pressure tank when you want to shut down you can replace the 62 gallon tank with something smaller. Your pump will cycle on and off more frequently but otherwise the system will work the same.

When I leave my house for more than a week I turn off the well pump and open a faucet until the water stops flowing. That way a burst pipe will only leak the water that's inside the pipe and can drain by gravity. If gone for months and you live where freezing is a possibility I would also drain the water heater like you mention.