How Does a Toilet Flush Valve Work?

Located in the centre of the tank, a toilet flush valve is a plastic or brass fitting that is attached to the bottom of the cistern tank. It is operated with a rubber or neoprene flapper, or a ‘float ball’, which is a mechanism in the toilet that sits against the valve opening and keeps water in the cistern tank (until the flush handle is operated).

When the handle is pressed, a chain or lift wire connected to the handle rod lifts the flapper away from the valve seat, which allows the water to flush down out of the cistern and fill the toilet bowl.

With the tank empty, the flapper will fall back down into the valve seat, sealing the opening and allowing water to refill the tank.

Integrated into the flush valve is a vertical overflow tube, that extends from the base of the flush valve, up into the tank. The role of this overflow tube is that it works to prevent water from overflowing the tank, and also to allow small amounts of water to flow down into and fill the toilet bowl as the tank is refilling.

A small refill tube at the top of the overflow tube allows a stream of water to flow down into the bowl during the refill cycle. This restores the level of standing water in the toilet bowl, keeping the trap sealed.