I have a 110 VAC solenoid and want to know what kind of circuit i should build to control it from my microcontroller?
If the solenoid is a 110V AC type and your internal supply is also 110V AC then you can only damage the solenoid by having it switched-on for too long and it overheats.

Ask your self - should the solenoid activate only for a short period of time i.e. the time it takes to fill the tank. If so there is likely to be some form of top-float switch that disables the solenoid.

I would imagine there is a water-low and water-high level switch to activate the solenoid correctly so look into this and if so then no problem. However, if there is only a water low switch, the MCU may have to activate the solenoid for a fixed period of time then time out; the assumption being that the water adequately fills the tank but doesn't overfill.

If your MCU is a 5V type then you'll need a BJT to activate the relay: -



The diode is to prevent back-emfs damaging the BJT when it switches-off the relay (inductive load).