The water meter swings left and right due to the flow of water through the meter. The rotation of the meter's gears is caused by the pressure difference between the incoming and outgoing water, which moves the gears accordingly. This movement is detected and recorded by the meter to measure water usage.

The reason for the left and right swing of the water meter is primarily due to the flow of water. Water flowing through the meter creates a pressure differential that causes the gears to rotate. The direction of rotation depends on the direction of the water flow. When water flows in one direction, the gears rotate in one direction, and when the flow reverses, the gears rotate in the opposite direction. This back-and-forth movement is what causes the water meter to swing left and right.

According to the American Water Works Association (AWWA), the average household uses approximately 80 to 100 gallons of water per day. The flow rate of water through the meter is typically measured in gallons per minute (GPM). The more water that flows through the meter, the faster the gears will rotate, and the more pronounced the swing will be. For example, a high-flowing water usage, such as running a faucet full-force, will cause the meter to swing more rapidly and with greater force compared to a low-flowing usage, such as a slow drip.

The swing of the water meter is also influenced by the pressure of the water supply. Water pressure fluctuations can cause the gears to rotate at different speeds, resulting in a more erratic swing. This is particularly noticeable during peak usage times, such as in the morning when many people are using water simultaneously for showering, washing dishes, and flushing toilets.

In conclusion, the water meter swings left and right due to the flow of water and the resulting pressure differential. The direction and intensity of the swing are influenced by the flow rate and the pressure of the water supply. Monitoring the swing of the water meter can help homeowners and utility companies identify potential issues with water usage and pressure, leading to more efficient water management and conservation efforts.