A well water filtration system diagram is really an order of operations. Each device has a job, and each one either protects or ruins the device after it, so the sequence is not a matter of taste. Read any good diagram left to right, from the wellhead to the house, and you will see the same logic: pressurize, remove solids, oxidize and remove metals, soften, polish, disinfect.
The standard sequence, wellhead to house
Water leaves the submersible pump, passes a pitless adapter and reaches the pressure tank, which is where system pressure is established. Everything downstream of the pressure tank is treatment. First comes a spin-down or sediment filter to catch sand and grit. Next the oxidizing stage and iron or sulfur filter, because oxidized metal must be caught before it reaches anything with resin in it. Then the softener for hardness. Then a carbon filter to polish taste and odor. Last of all a UV lamp, positioned so nothing downstream can recontaminate the water. Finally the line splits to the house, with an outside hose bib often taken off before treatment.
Why the order is not negotiable
Put the softener before the iron filter and oxidized iron fouls the resin, which is the single most common self-install mistake on a well. Put the UV lamp before the sediment or iron stage and cloudy water shields the bacteria from the light. Put carbon ahead of an oxidizer that uses chlorine and the carbon consumes the chlorine before it can do its work. Penn State Extension notes that softeners can remove dissolved iron when the pH is above 6.7, hardness is 3 to 20 grains per gallon and dissolved iron is under 5 mg/L, but that oxidized iron fouls resin. That single sentence is why the iron filter sits upstream.
The parts of the diagram people skip
A real installation drawing shows more than boxes in a line. Every backwashing vessel needs a drain line with an air gap, sized and pitched so it can actually discharge, and a brine tank needs its own drain and overflow. Each device needs a bypass valve so it can be isolated without shutting the house off. Sample taps before and after every stage let you prove which device is or is not working, and they cost almost nothing at install time. A pressure gauge before and after the sediment stage tells you when the cartridge is loading up. Vendor product pages for whole-house iron filters show these fittings on the units themselves.
Sizing the train to the house, not to the catalog
The diagram only works if each vessel can pass the flow the house demands. Two showers and a washing machine at once sets the peak, and a backwashing filter that is undersized will channel, meaning water carves a path through the media instead of contacting it. Undersized vessels also cannot backwash properly, because backwash needs a specific flow to lift and clean the bed. Get the well's yield, the pump's delivery and the household's peak demand written on the drawing before choosing tank sizes, and cross-check against our well water filtration system page for typical configurations by problem.
Questions people ask about well water filtration system diagram
Does the softener go before or after the iron filter?
After. Oxidized iron fouls softener resin, so the iron filter removes it first. Only modest dissolved iron in otherwise suitable water should ever be left to the softener.
Where does the UV lamp belong in the diagram?
Last, immediately before the water enters the house. UV needs clear water to work and leaves no residual, so nothing that could cloud or recontaminate the water may follow it.
Should outdoor taps be fed before or after treatment?
Before, in most cases. Irrigation and hose bibs do not need softened or filtered water, and taking them off upstream saves media, salt and backwash volume.
Do I need a drain for every stage?
Every backwashing vessel and every brine tank needs a drain with an air gap. Cartridge filters do not, but they do need clearance below the housing to change the cartridge.