After precipitation and filtration, the water flows in a waterway. The flow rate of this waterway is measured, and the required amount of sodium hypochlorite is injected.
A diaphragm pump is used and dual control—stroke length control and control of the number of rotations—is performed, which posed the following problem.

• If operation is performed with a reduced stroke length when the treated volume is small, injection defects occur due to gas lock (biting air).

The pump was replaced with a Smoothflow Pump.

• A wide range at up to 1:200 is supported just by controlling the number of rotations, which makes it possible for a single pump to handle both normal operation and strong rain.
• No stroke length control is performed, so gas lock no longer occurs even with a low flow rate.