A well chlorinator injects a measured dose of chlorine into the line as water leaves the well, so every gallon entering the house is disinfected continuously. It does two jobs at once: it kills bacteria, and it oxidizes dissolved iron, manganese and hydrogen sulfide so a filter downstream can catch them as solids.
Continuous chlorination is not shock chlorination
Shock chlorination is a one-off event: you pour a strong dose into the well, circulate it, let it sit, and flush it out. It sanitizes the well, the casing and the plumbing, and it is the right first step after a repair, a flood or a positive bacteria result. What it does not do is keep working, so if the well is being recontaminated by a cracked casing, surface water intrusion or a failed sanitary seal, the problem returns within weeks. A well chlorinator is the permanent answer: a small pump doses continuously so protection does not depend on anyone remembering anything. Repair the well first regardless, because a chlorinator fitted to mask a structural fault is treating a symptom forever.
The parts of a chlorination system
A complete system is more than the pump. A solution tank holds the diluted chlorine. A metering pump doses it, usually triggered by the well pump or by a flow switch so injection only happens while water is moving. An injection fitting introduces it into the line. A contact or retention tank gives the chlorine time to work before the water reaches anything else, and this is the component homeowners most often try to skip, which is why their system underperforms. Finally a carbon filter downstream removes the chlorine taste and any residual, and a sediment or oxidizing filter catches the iron and sulfur solids the chlorine created. Vendors sell these as complete well water treatment packages sized in flow steps for exactly this reason.
Contact time is the design, not a detail
Chlorine needs time in contact with the water to inactivate organisms and to finish oxidizing iron and sulfide. That time is bought with tank volume relative to your peak flow, which is why a retention tank sized for a small cottage fails in a family home with two bathrooms running. The other design variables are dose and pH: too little chlorine and the job is incomplete, too much and you are stripping it out downstream at extra cost, and chlorine works less efficiently as pH rises. Where the water is acidic, neutralization usually comes first. Get the design done from an actual water test, since a chlorinator dialed in by guesswork produces either untreated water or a house that smells like a swimming pool.
Running it safely
The routine is small but it is not optional. Mix and top up the solution tank before it runs dry, since an empty tank means an undisinfected supply that looks and tastes exactly like a treated one. Check the pump is actually stroking and the injection point is not scaled shut. Test for a chlorine residual after the contact tank periodically, and test for bacteria after the whole system, because that is the result that matters. Handle concentrated chlorine with gloves and eye protection and never mix it with anything else. Keep the carbon filter downstream on its change schedule, since an exhausted carbon bed lets chlorine taste through and, worse, becomes a place for bacteria to grow.
Questions people ask about well chlorinator
What is the difference between a chlorinator and shock chlorination?
Shock chlorination is a single sanitizing event for the well and plumbing. A chlorinator doses continuously, so every gallon entering the house is treated.
Does a well chlorinator remove iron and sulfur?
It oxidizes them so they become filterable solids. The removal itself happens in the filter downstream, which is why a chlorinator is fitted as part of a train.
Will my water taste like chlorine?
Not if the system is complete. A carbon filter downstream of the contact tank removes the residual chlorine and its taste before the water reaches the taps.
Do I still need a contact tank?
Yes. Chlorine needs time in contact with the water to disinfect and to finish oxidizing iron and sulfide, and tank volume is how that time is provided.