The simplest method of continuous chlorination of wells less than 75 gpm (gallons per minute) is by the use of a motor driven pump called a hypochlorinator.  The pump pulls chlorine solution out of a holding chamber and into the water to be treated.  Where the pipe from the pump joins the pipe carrying the raw water, the Venturi effect creates a small vacuum and pulls the chlorine solution into the water

Diagram of a hypochlorinator.

The hypochlorinator's pump can be adjusted to feed various amounts of chlorine solution.  Hypochlorinators can also be controlled to automatically work in sequence with the well or service pump.

It is often necessary to increase or decrease the amount of chlorine added to the water as conditions change.  

Hypochlorinators allow you to adjust the amount of chlorine in three ways.  You can adjust the stroke length or machine speed by varying the pulley size.  Both of these adjustments change the hypochlorinator feed rate - the speed at which the machine puts chlorine into the water.  You can also adjust the amount of chlorine added by changing the strength of the chlorine solution.  This solution is prepared by adding the proper amount of dry chlorine compound to water.