Whole-house water filtration

Whole-house water filtration is the permanent solution for households that draw from a private well, spring, cistern, or surface water source where the treatment burden falls entirely on the homeowner. A well that produces clean-looking water can still deliver elevated iron, coliform bacteria, nitrates, or hydrogen sulfide — none of which are visible and none of which municipal treatment will catch because municipal treatment does not apply. Sizing and sequencing a sediment-to-carbon-to-UV treatment chain correctly provides safe drinking water at every tap, shower, and appliance without requiring bottled water, point-of-use filters at every faucet, or continual manual treatment.

Get a water test before you buy anything

Every component decision in this page depends on what your source water actually contains. Installing UV without knowing you have an iron problem means iron oxide particles will coat and degrade the quartz sleeve within months, allowing bacteria to pass unirradiated. Installing carbon without a sediment pre-stage means sand and silt will exhaust your carbon media in weeks. See Water Testing for certified lab options before specifying any equipment.

Sizing for household flow rate

Flow rate — measured in gallons per minute (GPM) or liters per minute (L/min) — determines every piece of equipment you choose. A system sized too small drops household pressure to a trickle when two fixtures run simultaneously.

Calculate your peak demand:

Home Size	Bathrooms	Peak GPM (L/min)
Cabin / small home	1	6–8 GPM (23–30 L/min)
Standard home	2	10–12 GPM (38–45 L/min)
Larger home	3+	15–20 GPM (57–76 L/min)
Small farm / workshop	Multiple fixtures	20–40 GPM (76–151 L/min)

To calculate your specific peak: count every fixture that could run simultaneously (shower, toilet fill, dishwasher, washing machine, outdoor hose bib). Assign each fixture a demand of 1.5–2 GPM (5.7–7.6 L/min), then multiply by how many you realistically run at once — typically 2–4. That number sets the minimum rated flow for every component in your chain.

Filter housings and UV systems rated below your peak flow will create a pressure bottleneck even if every individual component functions correctly. Undersizing is the most common installation error.

Field note

A pressure gauge on the outlet side of each treatment stage reveals problems immediately. A sudden pressure differential across a filter housing tells you the cartridge is loaded and needs changing — often weeks before visual inspection or cloudy water would alert you. Affordable analog gauges paid back their cost on the first filter change.

The treatment chain: sequence matters

The sequence of treatment stages is not interchangeable. Each stage must protect the stage downstream from it, or the downstream stage will fail prematurely.

Standard well-water chain:

Source water → Sediment (20 µm) → Sediment (5 µm) → Carbon → UV → Distribution

Why this order:

Coarse sediment (20 micron) removes sand, grit, rust flakes, and large particulates. These particles would physically clog fine sediment filters and carbon media within days.
Fine sediment (5 micron) removes silt, fine clay, and particulates down to 5 microns. This stage protects the UV quartz sleeve — the single most important protection step for UV performance.
Activated carbon removes chlorine (if your source is a chlorinated municipal backup), organic compounds, pesticides, taste, and odor. It also removes trihalomethanes (THMs) and some heavy metals. Carbon placed before UV also removes any chemical UV inhibitors.
UV disinfection is the final stage. Water reaching the UV lamp must be particle-free and clear (turbidity under 1 NTU). UV delivers its germicidal dose by penetrating the water column — particles physically shadow bacteria and viruses, allowing pathogens to pass the lamp unaffected.

What UV does and does not do:

UV at the correct dose (NSF/ANSI 55 Class A, minimum 40 mJ/cm²) inactivates bacteria, viruses, Giardia, and Cryptosporidium without adding chemicals. It does not remove dissolved minerals, metals, nitrates, or sediment. UV is purely a biological disinfectant. If your source water has chemical contamination, UV addresses none of it.

Sediment filtration details

Whole-house sediment filters use cartridge-based or backwashing media systems. Cartridge housings in standard 4.5-inch × 10-inch (11 × 25 cm) or 4.5-inch × 20-inch (11 × 51 cm) sizes are the most common residential format.

Cartridge filter characteristics by size:

Housing	Cartridge capacity	Flow rate capacity	Use case
4.5" × 10" (11 × 25 cm)	Moderate	Up to 10 GPM (38 L/min)	1–2 bathroom home
4.5" × 20" (11 × 51 cm)	High	Up to 20 GPM (76 L/min)	3+ bathroom home or farm

Micron selection:

20 micron (first stage): Captures sand, grit, rust, and large debris. High sediment loads will exhaust this cartridge in weeks in some wells — that is its job.
5 micron (second stage): Captures fine silt, clay, some bacteria and cysts. This stage often lasts 3 months even when the 20-micron stage requires monthly changes.

Run both stages in series. Single-stage sediment filtration at 5 microns in high-sediment well water clogs within days.

Replacement schedule: Every 3–6 months at minimum. Heavy-sediment wells may require monthly changes on the coarse stage. A pressure differential gauge set (gauge before and after the housing) gives you real data rather than guesswork. When differential pressure across the housing exceeds 15 PSI (1 bar), change the cartridge regardless of elapsed calendar time.

Activated carbon filtration

Carbon removes what sediment filtration physically cannot: dissolved organic compounds, chlorine, chloramines, some pesticides and herbicides, hydrogen sulfide (rotten egg smell), and taste-and-odor compounds from organic decomposition.

Two formats:

Block carbon cartridges — dense, compressed carbon in a cartridge format. Fine pore structure (0.5–5 micron) provides both sediment removal and chemical adsorption. NSF/ANSI Standard 42 covers aesthetic contaminants (taste, odor, chlorine). NSF/ANSI Standard 53 covers health-effect contaminants (lead, volatile organic chemicals). Look for dual certification.
Granular activated carbon (GAC) media tanks — large vessels with backwashing capacity, suited for high-flow applications above 15 GPM (57 L/min). GAC tanks are more economical per gallon of water treated in high-demand homestead applications.

Replacement schedule: Carbon cartridges typically need replacement every 6–12 months, or at 100,000 gallons (378,000 L) treated — whichever comes first. Carbon becomes saturated with adsorbed contaminants and ceases to remove new ones, but it does not visibly indicate saturation. Stick to the calendar schedule. GAC media tanks require backwashing every 1–2 weeks and media replacement every 3–5 years depending on load.

Field note

A return of taste or odor to the filtered water is the clearest sign that carbon media is exhausted. If your household starts noticing that the water tastes like it did before treatment, change the carbon stage immediately — do not wait for the next scheduled replacement.

UV disinfection sizing

UV disinfection is rated by two specifications: flow rate in GPM and delivered dose in millijoules per square centimeter (mJ/cm²).

NSF/ANSI 55 Class A vs. Class B:

Class A (minimum 40 mJ/cm²): Required for well water, surface water, spring water, and any source with potential microbial contamination. This is the standard for off-grid and homestead installations.
Class B (minimum 16 mJ/cm²): Supplement treatment for water that is already considered microbiologically safe — typically post-municipal treatment. Do not use Class B on private well water.

Selecting a UV system:

Size the UV unit to your peak household flow rate with no reduction. A UV unit rated for 12 GPM (45 L/min) on a 15 GPM (57 L/min) household will exceed its rated flow under peak demand, reducing contact time and dose below the minimum required to inactivate pathogens. The UV unit's flow rating is a hard ceiling, not a target.

A whole-house UV system for a 3-bathroom home is a moderate investment. Units rated 12–15 GPM (45–57 L/min) at Class A are appropriate for most family homesteads. For farm use above 20 GPM (76 L/min), commercial-grade units represent a significant investment but cover the full distribution system including outbuildings.

Lamp replacement: UV lamps degrade over time and must be replaced every 12 months regardless of appearance. A lamp that appears to glow may be producing 50% or less of its original UV output after 9,000 hours — still enough to make the light visible, not enough to deliver an adequate germicidal dose. Set a hard annual calendar date and replace the lamp before that date. Keep one spare lamp on hand.

Quartz sleeve maintenance: The quartz sleeve surrounding the UV lamp must be cleaned every 3–6 months. Iron, minerals, and biofilm accumulate on the sleeve and block UV transmission. Many systems require an acid wash (dilute citric acid or proprietary cleaner) to restore clarity. A fouled sleeve can drop UV transmission by 30–50%, causing apparent Class A compliance on a timer while delivering actual sub-lethal doses to bacteria.

Well water vs. surface water configurations

The standard chain covers most private well water scenarios. Surface water — from ponds, streams, springs, or cisterns fed by rooftop collection — often requires modifications.

Well water configuration

Most private wells face a predictable set of contaminants:

Sediment from aquifer particles
Iron and/or manganese (discussed in the next section)
Coliform bacteria (from surface infiltration or casing damage)
Nitrates (from agricultural runoff or septic influence)
Hardness (calcium and magnesium scale)

The sediment-carbon-UV chain addresses sediment and biological threat. It does not address nitrates or hardness — those require ion exchange or reverse osmosis at the point of use. Water Testing for nitrates is essential on any well near agricultural land or septic systems; nitrate above 10 mg/L (the EPA maximum contaminant level) poses an acute risk for infants and requires dedicated treatment beyond what the standard chain provides.

Surface water and spring-fed configurations

Surface water collected from springs, streams, or rooftop catchment carries a higher and more variable biological load than most wells. The treatment chain adds a pre-filtration stage:

Source → Coarse screen/pre-filter → Sediment (50 µm) → Sediment (20 µm) → Sediment (5 µm) → Carbon → UV → Distribution

An additional screen or sock filter before the housing catches leaves, insects, and macro-debris that would immediately destroy cartridge filters. For spring-fed systems, see Spring development for the collection point design that minimizes surface contamination before water even reaches the treatment chain.

Surface water viral contamination is higher than groundwater. UV Class A at 40 mJ/cm² inactivates viruses including enteric viruses, hepatitis A, and norovirus. Do not omit or downgrade the UV stage on surface water systems.

Iron, manganese, and hardness treatment

Iron and manganese are the most common well water problems in North America and the most likely to surprise homesteaders who installed a treatment chain without testing first.

EPA secondary standards (aesthetic, not health-based): - Iron: 0.3 mg/L maximum - Manganese: 0.05 mg/L maximum

Both are below their health-effect thresholds at these levels, but at higher concentrations they cause orange-red staining on fixtures, laundry, and appliances; a metallic taste; and — critically — rapid degradation of carbon media and UV quartz sleeves through mineral fouling.

Iron treatment options

Ferrous (dissolved, "clear water") iron — iron dissolved in water that only becomes visible after oxidation. Concentration up to 2–3 mg/L can be handled by a greensand or Birm media filter placed before the sediment stages.

Ferric (particulate, "red water") iron — iron already oxidized and in particle form. A 5–20 micron sediment filter catches most of it, but a dedicated iron filter tank provides more consistent removal.

Chemical oxidation (chlorination + carbon): For iron above 3 mg/L, inject a small continuous dose of sodium hypochlorite (chlorine) ahead of the treatment chain to oxidize dissolved iron to particulate form, then filter it out and remove residual chlorine with carbon. This approach requires a chemical injection pump — an affordable piece of equipment — and converts a dissolved contaminant into a filterable one.

High-iron wells (above 5 mg/L) warrant consultation with a Water Quality Association (WQA) certified professional before specifying equipment. Iron at these concentrations can also indicate the presence of iron bacteria — a biofilm problem that requires shock chlorination of the well itself, not just point-of-entry treatment.

Manganese treatment

Manganese is removed by the same oxidation-filtration approach as iron. Greensand media (manganese greensand or Filox) is the standard media for combined iron and manganese removal. Regeneration of greensand media requires periodic potassium permanganate treatment or an air injection system — a detail often omitted from basic filter system marketing.

Water hardness

Hardness (calcium and magnesium) is not a health concern but causes scale buildup in pipes, appliances, water heaters, and UV quartz sleeves. If your water is hard (above 120 mg/L or 7 grains per gallon), a water softener using ion exchange resin placed after iron filtration and before the carbon and UV stages extends equipment life significantly. This is a moderate investment with ongoing salt cost. For whole-homestead applications without salt, template-assisted crystallization (TAC) conditioners are a salt-free alternative — they do not remove hardness minerals but change their crystalline form so they do not adhere to surfaces.

System monitoring

A whole-house treatment chain is not install-and-forget. Three monitoring points determine whether the system is working:

Pressure differential gauges — one before and after each filter housing. Rising differential = loaded cartridge. A 15 PSI (1 bar) rise signals immediate replacement, regardless of schedule.
UV intensity monitor — most Class A UV units include a sensor and alarm. If the alarm activates, treat all household water as biologically unprotected and replace the lamp immediately. Never disable or ignore the alarm.
Annual water testing — retest for coliform bacteria, iron, manganese, nitrates, and turbidity every 12 months. Well conditions change: casing integrity degrades, aquifer chemistry shifts seasonally, agricultural runoff varies year to year. Annual testing confirms that your treatment chain still matches your actual water chemistry.

Installation checklist

Commissioning and handoff

Before putting a new system into service, flush the entire chain with full-pressure water until outlet water runs clear. This clears media fines from new carbon cartridges — a carbon that has not been flushed will produce black-tinted water for the first several gallons. Run this flush to drain, not to household distribution.

After flushing, collect a water sample from the post-UV tap and submit it for coliform testing. A new installation is not confirmed to be functioning until a bacterial test comes back negative — the sediment and carbon stages can be visually verified, but UV performance cannot be confirmed without a lab result.

With a verified, tested treatment chain in place, your home water system achieves genuine independence from both municipal supply and continual manual treatment. For the well that feeds the system, see Well drilling and maintenance for casing integrity, pump sizing, and shock chlorination procedures that protect the source. For point-of-use filtering needs beyond the whole-house system — reverse osmosis for nitrates, or activated alumina for fluoride — see Water filtration methods for cartridge-level options.