When is well disinfection needed?
Well disinfection will be required after construction of a well and installation of the pump; laying of mains and service pipework; building of a water storage structure or if biological pollution has entered the water system – then the system should immediately be disinfected to kill any micro-organisms present.
Wells / Tubewells
- 10 x 8.68g NaDCC tablets are dissolved in 50 litres of water in an open area.
- Half the solution is poured into the well and the pump operated until the water is pumped out (or from all the opened taps in a household) and distinctly smells of chlorine.
- The pumping is stopped and the rest of the solution poured down the well.
- After waiting one hour water is pumped again (with all the household taps open) for several minutes.
- The pumping is stopped and the system left for at least 12 hours.
- After 12 hours the water is pumped to waste until the residual chlorine level is <2mg/l (2ppm).
- The system is then re-filled with potable water.
Spring Boxes or Silt Traps
- 10 x 8.68g NaDCC tablets are dissolved in 50 litres of water in an open area.
- The inside walls are scrubbed with the solution, especially between the water level and the highest point the water level may reach, using half the solution.
- The rest of the solution is poured into the well / box / trap.
- In the case of a pump facility, procedures 4, 5, 6 and 7 above should be followed.
- The water is run to waste to leave a residual chlorine level of <2mg/l (2ppm).
- The system is refilled with potable water.
Mains Pipe Disinfection
- 1 x 8.68g NaDCC tablet per 100 litres are made up in sufficient water to enter the mains pipework at the charging point and fill the entire system.
- The system is left for at least 24 hours. All the valves are operated at least once during this period to disinfect the fittings, valves and hydrants etc.
- Residual chlorine levels are taken at the point furthest from the charging point. Disinfection is repeated until the residual chlorine level is >10mg/l (10ppm).
- After disinfection the water is flushed out of the system to leave a residual chlorine level of <2 mg / l (2ppm).
- The system is refilled with potable water.
Service Pipe Disinfection
- 1 x 8.68g NaDCC tablet per 333 litres are made up in sufficient water to enter the service pipes.
- Once completely filled the pipelines are closed and left for at least 24 hours.
- After disinfection the water is flushed out of the system to leave a residual chlorine level of < 2mg/l (2ppm).
- The system is refilled with potable water.
Water Structure Disinfection
- 1 x 8.68g NaDCC tablet per 250 litres are made up in sufficient water to disinfect the water structure.
- The solution is distributed over the floor of the structure to a depth of 300mm.
- The solution can also be used to spray soffits, walls, columns etc. to ensure that all exposed areas are covered.
- After disinfection all of the water is flushed out to waste.
- The system is then refilled with potable water.