Sparge Tank/Mash Tun Leaking at the Valve

[BugAC]

So my Sparge Tank is leaking again. I use 2 10 gallon igloo water coolers for mashing/fly sparging with 1/2" stainless ball valves. The leak comes from the water following the threads on the inside of the nipple (not sure if correct terminology) that connects to the valve. I've used pipe tape on the threads to stop it in the past. And that works, for awhile, until it gets bumped, or if i decide to unscrew the hex nut for some reason or another.

Does anyone have a suggestion for a better way to stop the leaks?

 

[BugAC]

an update. I started looking at different designs and went home depot.

I went to the faucet repair section and got, what they called, 3/4" OD gaskets (in reality, they were smaller). In addition to the gasket included, i placed 2 more. I wrapped the pipe with some pipe tape. So looking from the inside out of my sparge tank you see.

Hex nut, included red gasket, washer, gasket, cooler wall, gasket, ball valve.