Use CasesPreventing defective injection to obtain a constant residual chlorine concentration in a small water

Liquid Type
Process Type


Local government (water department)

Customer's Needs and Problems

To supply safe tap water to a mountainous area, a small-scale water purification facility is used to filter and disinfect well water and discharge the purified water.
The residual chlorine concentration of the water tank was monitored and sodium hypochlorite was injected with a diaphragm pump, which posed the following problems.

  • When the temperature rises during the day, a phenomenon (gas lock) in which the gas generated from the sodium hypochlorite gathers inside the pump occurs, which sometimes leads to defective injection.
  • The water purification facility is unmanned, so an alarm would occur each time that the residual chlorine concentration dropped below a certain value due to the gas lock phenomenon. Then, a worker would rush to the facility and perform recovery work such as releasing the air.
  • The residual chlorine concentration continues to drop until the air is released, so delays in responding to the alarm pose the risk of water that is below the standard value being discharged from the facility.

TACMINA's Solutions

The sodium hypochlorite injection pump was changed to a DCLPW Series diaphragm pump, which is resistant against the gas lock phenomenon.

  • This pump is equipped with an “air block mechanism,” which prevents the intrusion of gas into the pump head, and an “automatic air release mechanism,” which automatically discharges any gas that does intrude into the pump head. These mechanisms make it difficult for the gas lock phenomenon to occur.
  • The frequency of defective injections was decreased greatly and the residual chlorine concentration was stabilized. This nearly eliminated the need for workers to rush to the facility.

Flow Diagram