Join Date: Jan 2008
The picture is blurry, but if that is the best you have, then I can work with that.
The "T" you describe appears to be the needle valve with a black phenolic knob.
The tubing feeds directly into a solenoid? I suppose your solenoid has some kind of NPT to hose barb adapters.
I am guessing that that from the solenoid, it goes to the bubble counter in the background, which then feeds into your aquarium.
You will need to remove the "T" (needle valve) if you are going to replace it. You might as well take this opportunity to place the solenoid first, and then the needle valve. You may also want to take this opportunity to fix up the wiring on the solenoid, as from what I can see the (green) wires are dangling about, and this can be dangerous.