Toilet cisterns -- or tanks, as they're called in the U.S. -- provide water that powers a flush in a toilet. Also, as opposed to the U.S. style of tanks, many cisterns utilise a device called a siphon valve to start the flow of water into the bowl. You can fit a toilet cistern to the back of your bowl to replace an old or cracked cistern.
Use a bathroom cleaner and rag to clean off the rear area of the toilet bowl where the toilet cistern will be installed.
Apply a light coat of silicone grease to the inlet at the back of the toilet bowl. This will help create a tight seal between the cistern and the bowl.
Lift up the cistern and align it so that the handle is on the front. Slowly lower the cistern over the back of the toilet tank. The gasket on the bottom of the cistern fits into the hole at the rear of the bowl.
Insert the cistern bolts through the bottom of the cistern so that they poke through the cistern and emerge at the bowl. There may be two, three or four bolts.
Thread the nuts onto the bottom of the cistern bolts. Tighten with a wrench.
Wrap the inlet on the cistern with plumber's tape. Do the same thing for the outlet on the water supply valve nearby. Connect a water supply hose to the water supply valve. Connect the other end to the inlet on the toilet cistern.
Turn the handle on the water supply valve to the left. The toilet cistern will begin filling. Flush the toilet and check for leaks. Tighten the cistern bolts, if needed. Place the lid on top of the cistern.