There are some really primitive (cheap) drain valves on tanks. I bought some nice brass 1/2 turn valves for my 20+ year old EmgloWell, dammit. I set it for 100 psi and left it overnight. Today, I am down to 10 psi. I believe I will recharge the tank, then use soap and water to find my leak. As I type this, I just realized I may have not tightened the water drain fitting tight at the bottom of the tank, and could be a source of some of the leak. I will unscrew this fitting, add some pool o ring silicone, then cinch down the thumbscrew a bit better.