It is accurate to being easy to check to see if it holds water. I bought a used tank once that was fine for a couple of months and then my wife and I woke up and stepped out of bed into water. That kind of sucked. My feelings on buying used tanks goes like this. If it is a killer deal go for it. If it's just saving half it might be worth just buying new and having the warranty with the tank. There is a LFS to me that has monthly used equipment sales and they list the used stuff at 25% of the retail price. If it doesn't sell that month they try the second month at 10% of retail price. I would totally chance it at 90% off, but I see allot of tanks on craigslist that are only a little lower than buying new.