The cistern that is fitted to your WC is quite a modern piece of technology these days, being fitted with very efficient flushing devices. Brief history:Pre 1993, a 9ltr or imperial 2 gallon capacity cistern was fitted. However, this capacity was lowered in an attempt to save water in the first instance to 7½ltrs. This was changed also to the capacity we use today of 6 litres.Basic Operation:In the old system the water supplied to the cistern was maintained and controlled using an old valve operated by a float. This would sit on top of the water and lowered as the level dropped when flushed. At its lowest point it would open a filling valve or inlet and the water would rise again, filling the cistern and lifting the float once more. The old systems would use a “Siphonic” device, but now this happens via a valve lifting letting the water flow. There is a device employed to shut off when the most effective volume of water has been discharged. Enfield Plumbers fit toilet systems.The Siphonic Affect:This action or affect happens as water vacates any container having no mechanical help. It will move up and over a tube shaped like an upside down ‘J’. It’s longer leg attaches to the flush pipe and it’s shorter leg is open to the water contained in the cistern. When the air is evacuated there is a partial vacuum and is started by a large diaphragm washer lifting and letting a quantity of water to discharge away through the flush pipe with the air causing the partial vacuum. An Enfield Plumber EN2 is familiar with this type affect.Flush Buttons:There are nowadays, two buttons installed on the top of the modern cistern. The buttons are slightly different sizes and sometimes shapes also. This is to denote that you have a choice of two flushes:1). Bigger button for longer and more water volume flush.2). Smaller Button for shorter and less water volume flush.