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Clack Retention Tanks
Fiberglass retention (contact) tanks for well water chlorination and peroxide systems — Clack RT40, RT80 and RT120, shipped free with the in/out head, fittings and blow-down drain included. Sizing help and specs are below the products.
Retention tanks (contact tanks) for well water treatment
A retention tank — also called a contact tank or chlorine contact tank — is a plain fiberglass vessel that gives treated water time. When you inject chlorine or hydrogen peroxide into a well line to kill bacteria or oxidize iron and sulfur, the chemical needs 10–20 minutes in contact with the water before the carbon filter downstream strips it back out; the retention tank is where that happens. It also lets oxidized iron and sediment settle and be purged through the blow-down drain instead of loading your filters. Every Clack retention tank here ships free with the 1190RT in/out head, fitting kit, 1″ blow-down drain and a 5-year limited warranty.
What size retention tank do I need?
Size by contact time: your peak flow in gallons per minute multiplied by the minutes of contact you need. A typical home drawing 8–10 GPM that wants 10–12 minutes of chlorine contact lands on an 80- or 120-gallon tank; the 40-gallon RT40 suits low-flow homes or peroxide systems that need less dwell time. When in doubt, go up a size — more contact time never hurts treatment, and the tank is the cheapest part of the system to oversize.
Retention tank vs. pressure tank
They look similar and both sit on the well line, but a pressure tank stores pressurized water for your pump; a retention tank stores treatment time and has no air cell or bladder. Most chlorination systems need both. Full explanation in our retention tank vs. pressure tank guide; shop WellMate pressure tanks separately.
Clack retention tank models
| Model | Capacity | Size (dia. × height) | Connections | Price |
|---|---|---|---|---|
| Clack RT40 (C2250) | 40 gal | 21.5″ × 43.5″ | 1¼″ NPT | $539 — currently out of stock |
| Clack RT80 | 80 gal | 21″ × 69″ | 1¼″ NPT | $999 |
| Clack RT120 (C2252) | 120 gal | 24″ × 80″ | 1¼″ NPT | $1,199 |
What's included with each tank
Clack 1190RT in/out head, 1¼″ × 1½″ PVC solvent straight fitting kit, two 1¼″ plastic male NPT fittings, 1″ blow-down drain at the base with 360° orientation, baffle diffuser for chemical mixing, C-Series bypass, grey fiberglass with epoxy resin liner. Max working pressure 315 PSI; not for prolonged use above 140°F.
Building a chlorination system? See our well water chlorination system with Stenner pump, then follow the retention tank with a backwashing carbon filter. Treating iron or sulfur without chemicals? An air-injection iron filter may not need a retention tank at all — call 800-374-2143 and we'll lay out the train.
