A ball valve.The float valve in the brine tank (inside plastic pipe) also can get clogged up with salt residue....
For hanging coat hooks, tightening door hinges and replacing washers in the toilet-tank float valve you'll need a set of screwdrivers.
Not sure if you use swamp coolers down under, but the float valve is similar to what is in the tank of your toilet (except much smaller) to regulate water flow.