Pull the Plasplugs tile cutter's electrical plug from the wall outlet.
Lift the water reservoir's cover, the tray to the right of the tile cutting blade, off the Plasplugs tile cutter. Set the reservoir cover aside.
Turn the cutting blade's locking nut counterclockwise with an adjustable wrench until the blade shaft releases the nut. Pull the locking nut and washer from the blade shaft.
Slide the tile-cutting blade off the blade shaft and lower the blade into the Plasplugs tile cutter's water reservoir. Slide the blade toward the edge of the water reservoir and remove the blade from the saw.
Place the new tile-cutting blade in the Plasplugs tile cutter's water reservoir and slide the blade toward the saw's blade shaft, keeping the blade's directional arrow facing up. The blade has a directional arrow stamped into one side.
Reach into the water reservoir and grip the blade. Slide the blade onto the Plasplugs tile cutter's blade shaft, keeping the directional arrow facing away from the tile cutter's motor.
Slip the washer and locking nut onto the blade shaft. Tighten the locking nut with the adjustable wrench.
Replace the Plasplugs tile cutter's water reservoir cover.