Things You'll Need
Water-filled spray bottle
Pumps, vents and drains all require that holes be made in a plastic water tank prior to installation. Incorrectly drilling a plastic water tank will result in the tank cracking around the hole, damaging the tank. Repairing a cracked or damaged water tank will increase the money needed to complete a project. Using the correct tools and methods will allow you to drill any size hole in any type of plastic water tank without causing damage to the fragile walls of the tank.
Mark the location of the hole on the surface of the tank with a paint marker. Determine the size of the hole required to install your particular accessory.
Secure the correctly sized hole saw in the chuck of a drill motor. Place the point of the hole saw pilot bit on the mark you made on the surface of the plastic tank. Pull the trigger of the drill to slowly drill a pilot hole in the tank wall. Stop drilling when the pilot hole penetrates the plastic.
Coat the hole saw and the side of the plastic tank by spraying them with water from a water-filled spray bottle.
Drill into the plastic tank using moderate pressure while constantly spraying water on the area where the hole saw makes contact with the plastic tank. Use light pressure on the handle of the drill when the teeth of the hole saw are nearly through the tank wall. Pull the hole saw from the tank after you have completed the hole.
Sand the edges of the drilled hole with 120-grit sandpaper to remove plastic particles and sharp edges from the drilled wall of the plastic tank.
Avoid using solvent-based markers to ensure the ink does not react with the plastic tank.