Heating issues? Water boiling out?

[Wolfblaine]

I am a noobie at cars but will do my best to explain the situation. About a week ago we noticed that the temperature gauge was at its halfway mark. A quarter higher than it usually is. Also began noticing that the water that we put into the container would boil out after about 20-30 minutes of driving it. The fan in the front only turns on when we have the A/C on. We originally thought it was this fan that had crapped out on us, swapped fuses/relays and checked the plug.
We fill it with water every time it boils out and will try to keep the a/c going while driving it to keep the temperature down but do you gs have any advice or input for me? I've been to two different mechanics and theyve told me that the problem is two different things.
Edit: we have observed for leaks and can not find any. The only liquid that is departing is the water that boils out. With the a/c on the temp stays low because the fan is on, I think. Also if it matters the a/c does not actually blow cold air or anything. Hasn't for about a year haha.