A common layout is pump → pressure tank → coarse sediment as needed → iron/sulfur filter → softener → fine prefiltration if required → UV → house. Exact order can change with chemical feed, pH correction or specialty equipment.
Pressure tank comes early
Standard whole-house treatment is normally installed after the pressure tank so the equipment receives stable pressurized flow.
Iron treatment before softening
Dedicated iron removal upstream protects ion-exchange resin from heavy iron loading and lets the softener focus on hardness.
UV belongs near the end
UV performs best on already-treated clear water. Upstream sediment and chemistry control help the chamber receive water with fewer interfering particles and color.
Do not build the train without lab data
Bacteria, nitrate, arsenic, pH, iron, manganese and hardness can require different technologies. CDC recommends routine private-well testing and certified laboratory analysis.
Testing and treatment order for Well-Water Treatment Order for Iron + Hardness + UV
Private-well treatment should start with measured water chemistry. Iron, manganese, hardness, pH, sulfur and sediment can interact, and bacterial concerns require a different treatment step from aesthetic staining or odor. A symptom can point toward a likely cause, but it is not a substitute for a source-appropriate laboratory or field test when equipment selection depends on concentration.
Treatment order matters because each stage protects the next. Coarse sediment is generally removed before media tanks, iron or sulfur oxidation is commonly handled before a softener when loading is meaningful, and UV disinfection is most reliable after upstream treatment has reduced turbidity and interfering material. The correct train depends on the actual chemistry rather than a one-size-fits-all diagram.
Size for service flow and backwash—not only household count
Whole-house equipment has to treat water at the rate the home actually uses during peak demand. Add simultaneous showers, laundry and fixtures, then compare that demand with the system's continuous service-flow rating. A treatment tank can remove the target contaminant in a laboratory and still be the wrong size if it causes a noticeable pressure drop in the home.
Backwashing systems also need enough pump capacity to clean the media bed. Oversizing a tank can create its own problem when the well pump cannot deliver the required backwash flow. Check both service flow and regeneration requirements before buying, and include ongoing media, chemical, electricity and maintenance costs in the decision.