# How a well water treatment system is laid out

> The order of components in a well water system decides whether each stage works. See the standard chain, why it runs that way, and what to place first.

Canonical: https://watertreatmentpro.com/well-water-system-layout/

Last updated: 2026-11-09

A well water treatment system is laid out as a chain, not a collection of boxes. Water leaves the pressure tank and passes through sediment filtration, then iron or sulfur removal, then softening, then carbon, then UV, then the house. Each stage exists to protect the next one, and swapping two components usually costs more in service calls than the swap saves in fittings.

## The Standard Chain and Why It Runs That Way

The layout follows one rule: remove the thing that damages the next stage before the water reaches it. Sediment blinds UV lamps and clogs resin beds. Iron fouls cation resin permanently at high enough levels. Chlorine shortens the life of reverse osmosis membranes. Hardness scales every heat exchanger downstream.

| Position | Component | Protects |
|---|---|---|
| 1 | Pressure tank | Steady pressure for all stages |
| 2 | Sediment filter | Iron filter, softener, UV sleeve |
| 3 | Iron or sulfur filter | Softener resin |
| 4 | Water softener | Water heater, fixtures, RO membrane |
| 5 | Carbon filter | UV sleeve, taste and odor |
| 6 | UV purifier | Final barrier at point of entry |
| 7 | House piping | Everything above |

That is the default. A house with no iron and no sulfur skips position 3. A house on a private well with bacteria skips nothing. A municipal supply usually starts at position 5, since the utility has already handled sediment and iron.

## Position 1 and 2: Pressure Tank and Sediment

The pressure tank is not treatment, but it is the first thing in the layout and it sets the pressure every downstream stage sees. A tank that has lost its air charge causes short cycling, and short cycling hammers valve bodies on softeners and filter heads. If your pressure gauge swings between 30 and 50 psi every few minutes with no water running, fix that before buying anything else. The relationship is covered in [pressure tank and treatment](https://watertreatmentpro.com/pressure-tank-and-treatment/).

Sediment filtration follows. A 20 micron cartridge catches sand and grit from the pump; a 5 micron cartridge protects the UV sleeve and the softener's injector. On wells with visible turbidity, a spin-down sediment trap ahead of the cartridge saves cartridges, because it dumps the heavy load to drain instead of storing it in pleats. Cartridges are cheap and frequent: replacement intervals run 3 to 6 months depending on load, and the cost sits in the tens of dollars per cartridge, not hundreds.

## Position 3: Iron and Sulfur Before the Bed

This is the position people get wrong. A standard softener can handle a small amount of iron, commonly up to 2 to 3 ppm, because the resin exchanges it along with calcium and magnesium. Above that, iron coats the resin beads, regeneration cannot strip it, and capacity falls permanently. The bed does not recover with more salt.

So an iron filter goes ahead of the softener whenever the lab report shows iron above that range, or whenever there is any sulfur odor. The mechanism differs by unit. Air-injection filters oxidize dissolved iron into a particle and backwash it out. Catalytic media do the same job with a different contact surface. Sulfur needs oxidation plus a carbon stage behind it. Installed cost for iron filtration runs $800 to $2,500; sulfur units run $1,000 to $3,000. Read [iron in well water](https://watertreatmentpro.com/iron-in-well-water/) if the report shows a number you do not recognize.

## Position 4: The Softener and Its Sizing

Softening is ion exchange. Water passes through a bed of strong acid cation resin charged with sodium, and calcium and magnesium swap onto the resin in exchange for sodium. Hardness categories that matter for sizing are 0 to 3 GPG soft, 3 to 7 moderate, 7 to 10 hard, and above 10 very hard.

Layout affects sizing in a practical way. The softener must handle the house's peak flow without excessive pressure drop, which is a different limit from its grain capacity. A 48,000 grain unit with a 1 inch valve is a common mid-size choice; the [capacity versus flow rate](https://watertreatmentpro.com/water-softener-capacity-vs-flow-rate/) distinction explains why a big tank can still be the wrong pick for a house with four bathrooms.

Placement rules are simple. Put it after the iron filter, before the water heater, on a level surface, within hose reach of a drain, and with at least 18 inches of clear space above the brine tank for salt loading.

## Position 5 and 6: Carbon and UV

Carbon goes after the softener for two reasons. First, it removes chlorine and chloramine, which would otherwise degrade the resin and any downstream membrane. Second, it polishes taste and odor. Granular activated carbon and carbon block differ in contact time and particle shedding, a distinction covered in [carbon block versus GAC](https://watertreatmentpro.com/carbon-block-vs-gac/). Cartridge life runs 6 to 12 months, at $80 to $300 per year.

UV goes last because UV needs clear water. Turbidity, iron film on the quartz sleeve, and hardness scale all reduce the dose reaching microorganisms. A lamp behind a dirty sleeve is a lamp doing nothing. Lamps are replaced every 12 months at $30 to $90, and the sleeve is cleaned at the same visit. See [UV purifier cost](https://watertreatmentpro.com/uv-water-purifier-cost/) for the install arithmetic.

## Planning the Layout in Five Steps

1. **Pull a lab report.** A $40 to $150 panel gives you hardness, iron, manganese, nitrate, pH, and bacteria. Every placement decision follows from those numbers.
2. **Measure the wall.** A full chain needs roughly 6 to 8 feet of wall, plus 30 inches of clear floor in front of the softener and filter for service.
3. **Sketch the order on paper.** Mark the entry point, the pressure tank, the drain, and the nearest outlet. Components that need drain lines are the iron filter, softener, and any backwashing carbon unit.
4. **Confirm drain and power before buying.** A backwashing valve needs a drain within about 30 feet and a GFCI outlet within cord reach. Missing either changes the labor line substantially.
5. **Install a three-valve bypass at the entry.** It lets you isolate the whole train for service while keeping raw water available to the house.

## What the Layout Costs

Installed prices for the individual stages are published ranges: sediment and carbon filtration $500 to $1,800, iron filtration $800 to $2,500, sulfur $1,000 to $3,000, softening $1,200 to $4,500 installed. A full chain on a hard, iron-bearing well commonly lands between $4,000 and $9,000 in equipment and labor, before any reverse osmosis at the kitchen tap.

The number that matters is not the total but the order. A $2,000 softener placed ahead of a $1,500 iron filter will need a $300 to $600 resin rebed years early, which erases the savings from skipping the filter. Test first, lay out the chain from the test, and buy in that sequence. If you are still deciding between softening approaches, [salt-based versus salt-free](https://watertreatmentpro.com/salt-based-vs-salt-free-softener/) covers what each does to the rest of the layout.