Manifold Leaking

I have one of those manifolds with the red handles and mfl fittings. Washers in my metal to metal connections.  During my dunk test, there is a very slow leak coming from the handle. But a bigger leak as the handle moves from open to close or close to open. How do I resolve this leak?

First I don’t have one. Second good on you for checking before hooking everything up and draining your tank.

Looking at the photos it seems those valves can be disassembled. I’d wager you have a packing/Teflon seat/o-ring that is the culprit. It already leaks so you can’t use it so I’d disassemble it and take a look. Worst case you have to replace that valve. …but I’ll bet an airport beer that it’s a packing/Teflon seat/o-ring that is replaceable.

I’ve had the same problem with several of those valves. Different ones can be found on line. I had an old regulator with a splitter and 2 valves that I used.

Valves can leak when partially opened. The bore is basically leaking into the body which isn’t pressure tight.