The concentration is calculated on the volume of water that is in the well. The concentration must be at least 200 milligrams of chlorine per litre of water present in the well and must be left in the well for at least 12 hours to ensure any bacteria present are.
idles; idled; idling. Learner's definition of IDLE. 1. of an engine or vehicle: to run without being connected for doing useful work. [no object]. She left the engine idling for a few seconds before she turned it off. The cars idled in traffic.
1 If the car idles rough or cuts off at low RPM or idle, the cause could be a failing O2 sensor. The O2 sensor is out of the loop at full throttle and will not affect the way the car runs.  A rough idle can also be caused by a problem with the air flow box.