Unplug the Beckett waterfall pump power cord from the electrical outlet. Loosen the clamp securing the pump hose to the waterfall tank with a Philips-head screwdriver. Pull the hose away from the tank.
Remove any pump vault covering and lift the waterfall pump out of the vault. The pump vault hoses the pump and the lid simply snaps on and off. Pull the pump hose off the top of the waterfall pump where it connects to the adapter nipple. There is no clamp at this connection and the hose pulls straight off.
Turn the front screen 1/4-turn counterclockwise with your hand to unlock it from the pump housing. The screen is the front portion of the housing with the slots. The adapter also connects to the top of the screen assembly.
Pull the screen assembly away from the pump housing. There is a gasket between the screen assembly and housing that you must remove at this time. Take the screen assembly, gasket and tubing to a sink.
Fill the sink with warm water and 1/2-cup of vinegar. Pull the volute out of the screen assembly. The volute is the inner solid portion of the assembly. Some screens have a replaceable filter pad. Pull the filter pad out of the main screen assembly. Submerge the parts, except for the disposable screen filter pad, into the sink water and scrub with an old toothbrush. Rinse clean in water.
Place a new filter pad into the inside of the screen assembly. Insert the volute into the screen assembly, lining up the adapter with the notch on the assembly. Place the gasket on the notch of the front of the waterfall pump housing. Line up the screen assembly locking tabs with the inner notches on the housing. Turn the screen assembly clockwise to lock it to the housing.
Set the waterfall pump into the vault. Push the pump hose over the adapter nipple until the end of the hose is flush with the top of the screen assembly. Push the pump hose over the tank nipple and secure with the clamp. Plug the waterfall pump power cord back into the electrical outlet.