How The Toilet Works

Basic Operation

When a toilet is ready for use, both the tank and the bowl are partially filled with water. As the toilet is flushed, the water in the tank enters the bowl which forces the water in the bowl through the drain channel. The velocity of the water draining creates a level of suction which pulls the contents of the toilet bowl down the drain. Once the tank is empty, the tank and bowl slowly refill.

Trapping the Sewer Gas

If you were to look at a cross section of a toilet, from the bowl to the drain in the floor, you would see an S-shaped channel. The S-shaped channel acts as a trap that keeps the water level in the bowl equal to the highest part of the S-shaped channel. The channel prevents sewer gasses from entering the house by maintaining water in the bowl.

Flush Valve Assembly

The flush valve assembly is the mechanism inside the tank that regulates the water during the flush operation of the toilet.  This assembly usually consists of the following components. A float ball,  called the ballcock, is attached to the inlet valve. The ball rises and falls with the water level in the tank.  When the ball rises to a certain level, the inlet valve controlling the incoming water is turned off and  the tank stops filling.  The water enters the tank through an inlet tube to the inlet valve and down through the fill tube.  The fill tube is used to direct the water into the tank.

The flapper is a rubber or plastic flap at the bottom of the tank.  The flap covers the opening, called the flush valve seat.  When the toilet handle is operated, the flapper is lifted, which causes the water in the tank to enter the toilet bowl.

The tanks on older toilets vary in size/capacity from 5 to 7 gallons.  All new toilets are required to be 1.6 gallons or less.