DrewE wrote:
I'm assuming gas means gasoline here, and not some gaseous compound.
According to what I found with a quick googling, gasoline doesn't particularly attack/affect PEX tubing. If it were mine, I would perhaps try rinsing thoroughly with water, then letting water with dish (or dishwasher) detergent sit in it or preferably circulate through it for a time, and then thorough rinsing again. I'm not suggesting this is a foolproof, hospital-grade procedure; just that offhand it's an approach I likely would take.
Ditto and I spent 32 years doing chemical cleaning. Just so long as the whole system is flushed, tank included, you should be OK. Your nose will tell you if it is clean. I would not replace the tank until I do a couple of flushes/soaks and they fail.