Toilet Tank Water Regulations

Federal Regulations

• Before 1992, the standard toilet tank held 3.5 gallons of water. In an effort to reduce household water usage, the United States federal government enacted the Energy Policy Act. Among its mandates, the Act lowered the tank volume from 3.5 to 1.6 gallons. The smaller tank reduces the amount of water used during each flush. The modern toilet tank holds just enough water to provide the force required to empty the contents of the bowl.

Toilet Tank Operation

• A pull of the toilet's flush handle opens a valve inside the bottom of the tank. The open valve permits the maximum 1.6 gallons of water inside the tank to flow into the bowl. The force of the flowing water discharges the contents of the bowl down the waste pipe. With the tank empty, the valve inside the tank closes. A fill valve, also located inside the tank, replenishes the tank's 1.6 gallons of water. A float ball or float cup attached to the fill valve allows for adjustment of the water level.

Water Level Adjustment (Float Ball)

• A screw atop the fill valve allows the attached float ball to rise to a predetermined height. Setting the height properly ensures that the tank holds neither more nor less than the allotted 1.6 gallons of water. Setting the height entails turning a screw located on top of the fill valve. Turning the screw clockwise lowers the water level, while turning it counterclockwise raises it. A mark on the side of the overflow pipe indicates the required water level, which is at least 1 inch from the top of the overflow pipe.

Water Level Adjustment (Float Cup)

• Like the float ball, the float cup determines how much water the fill valve empties into the tank before shutting off. The float cup includes a lift rod and spring clip. Adjusting the height of the float cup requires first pinching the spring clip, then raising or lowering the float cup as needed. The float cup should be adjusted, if necessary, so that the water rises no higher than 1 inch from the top of the overflow pipe.