TA 40 (was 100 a month ago with very little usage since)
i noticed two things about the bleach I bought at Walmart. It is 8.25% but the available Chlorine is 7.86. In addition, it is not a gallon it is 121 ounces.
3 gallons of that in along with a quart of Polyquat 60.
Let it swirl for a few hours and shut off pump.
Will remove hoses and drop the water level to below the eyeball maybe. Might just insert the plug. I leave the gate valves open so if it leaks a little it won't freeze and burst.