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Well Water Chlorination Systems
Well water chlorination systems: chlorine injection with a Stenner metering pump, Clack retention tanks for contact time, and backwashing carbon to strip the chlorine back out, for wells with iron bacteria, heavy iron, high hydrogen sulfide or recurring coliform. Complete systems ship ready to install, or build the train from the components below. Free shipping. When a well needs chlorination instead of an air-injection filter, how the three stages work, and how to size the tank, below the products.
When a well needs a chlorination system
Most iron and sulfur wells are handled by an air-injection filter with no chemicals at all. Chlorination is for the wells those filters can't keep up with. A chlorine injection system feeds a small, metered dose of chlorine into the water whenever it flows, gives it time to work in a retention tank, then removes the chlorine with carbon before the water reaches the house. It's the strongest oxidizer and disinfectant available for a private well, and it handles several problems at once.
| Your well | Air-injection filter | Chlorination system |
|---|---|---|
| Iron up to ~10 ppm, sulfur up to ~5 ppm | Yes, the usual choice | Works, but more than you need |
| Iron above 10 ppm, or H₂S above 5–6 ppm | Overwhelmed; frequent fouling | Yes |
| Iron bacteria (slimy red-brown film, swampy smell) | Bacteria foul the media | Yes; kills the bacteria and oxidizes the iron |
| Sulfur-reducing bacteria that return after shock chlorination | Partial | Yes; continuous residual keeps them down |
| Recurring coliform positives | No | Yes, or UV on clear water |
| Tannins or organics with iron | Limited | Yes, with carbon after |
If a single shock-chlorination of the well clears the problem for good, you don't need a system. If the smell, staining or bacteria come back within weeks or months, continuous chlorination is the permanent fix.
How a chlorine injection system works
- Metering pump. A Stenner peristaltic pump draws chlorine solution from a tank and injects it into the line through a check valve. A flow switch turns the pump on only when water is moving, so dosing follows use.
- Retention (contact) tank. Chlorine needs time to oxidize iron and sulfur and to kill bacteria. A Clack retention tank holds the water long enough to finish the job and lets oxidized particles settle.
- Backwashing carbon filter. Removes the leftover chlorine, the taste and odor, and any remaining precipitate, then backwashes it to drain. Catalytic carbon handles chloramine and trace sulfur better than standard carbon.
Optional: a backwashing sediment filter after the tank on very high iron, and a softener after the carbon for hardness.
Sizing the retention tank
Size the tank for about 10 minutes of contact time at your peak flow: peak GPM × 10 = gallons of tank. Iron bacteria and heavy H₂S may need longer, which means a larger tank or a slightly higher chlorine dose.
| Peak flow | Typical home | Retention tank |
|---|---|---|
| Up to 4 GPM | Cabin, 1 bath | Clack RT40 (40 gal; from $539) |
| 5–8 GPM | 1–2 baths | Clack RT80 (80 gal; from $999) |
| 8–12 GPM | 2–4 baths | Clack RT120 (120 gal; from $1,199) |
Target 0.2–0.5 ppm free chlorine at the outlet of the retention tank, measured with a test kit, and adjust the pump until you hold it. The carbon filter then takes it to zero.
Systems and components
| Stage | Clack | Fleck |
|---|---|---|
| Complete system: pump, solution tank, flow switch, RT120, carbon filter, test kit | 15 GPD Chlorination System with Stenner Pump (up to 2,000 GPD; from $4,229) | Build with the Fleck carbon stage below |
| Backwashing carbon (dechlorination) | Backwashing Carbon Filter (WS1; from $1,099) | Fleck 2510 AiQ Backwashing Carbon (from $1,199) |
| Retention tank | Clack RT40, RT80, RT120; fit ahead of either valve | |
| Chemical feed pump only | Crystal Quest Dosing System (chlorine option; from $792) | |
| Catalytic carbon media | Jacobi catalytic · Centaur catalytic | |
Frequently asked questions
What chlorine do I use? Plain unscented sodium hypochlorite: household bleach (5–8%) or pool chlorine (10–12.5%), diluted in the solution tank. Never scented or "splash-less" bleach, which contains additives.
Will my water taste like chlorine? No. The carbon filter after the retention tank removes it. If you taste chlorine at the tap, the carbon is exhausted or undersized.
How is this different from shocking the well? Shock chlorination is a one-time high dose to disinfect the well and plumbing. A chlorination system feeds a small continuous dose, for problems that keep coming back.
What about the Stenner pump on its own? The complete system uses a Stenner 15 GPD adjustable pump; for a pump-only setup, the Crystal Quest dosing system is the standalone option. Call us if you need a specific Stenner model.
How much maintenance? Refill the solution tank every few weeks, check the chlorine residual weekly at first and monthly once stable, replace the pump tube annually, and rebed the carbon every 3–5 years.
Send your water test (iron, manganese, H₂S, pH, bacteria) and pump details with a quote request, or call 800-374-2143. Related: iron filters · sulfur filters · retention tanks · retention tank vs pressure tank · well water filtration systems.
