Cristo Balete wrote:Stacy, what you could do is install a valve there. Mark the spot first before you lower the water level. If it's a 1" leak, get a 1 1/2" or 2" valve that screws into a tank fitting (like the black plastic one below, not a metal fitting) that fits through the wall in a drilled hole the size of the male threaded part of the fitting that will go to the inside of the tank. There's probably already a tank fitting on it where the valve is that you can see as an example. Even if you can't get inside, you run a string or rope in through the new bottom opening in the tank, keeping a foot or so outside of the tank, either held by someone or taped to the exterior of the tank. Catch the rope or string with a tool of some sort and pull it up through the top opening of the tank. So you've now got a straight line from the top of the tank to the new opening.
Someone on a ladder puts the washer on the rope at the top, and put the male part of the fitting through the hole at the bottom, with the string sticking out the fitting (before you screw the valve into it.) Let the washer slide down the tight rope to the male projecting piece that is inside the tank, and carefully make it land on the male threaded end and pull tight on the rope, taping the rope at the top with duct tape, to the top of the tank, if there's only one person, while the person on the outside sticks their finger through the fitting and lines up the washer with the male threads, hold it with a finger while screwing it tightly from the outside. That will seat the fitting to the tank wall through the new hole. Then when that is nice and tight, screw in the valve, making sure it is closed, and refill the tank.
A valve and a fitting might cost about $10 or so.
It might take a day or so for the new fitting to be wet and expand to a tight seal.