Whole-house water, decoded.
A whole-house system treats every tap, shower and appliance. It is the right tool for some problems and the wrong one for others, and many systems sold for it carry no certification at all.
7 of 17systems below are on a certifier’s listing
Three checks before you buy
1. Know what is in your water.
On city water, look up your utility’s report. On a well, start with a certified lab test. Treatment follows the result, not the other way around.
2. Match the kind to the problem.
Carbon, softeners, iron filters and UV each do one job. What each kind does.
3. Check the listing, not the box.
“Tested to NSF standards” is not a certification. Every system below links to its listing, or says plainly that it has none.
Every system, and what it can prove
Certified systems first. Five-year cost is equipment and replacement media at the makers’ list prices for a household of 3 using 80 gallons each a day, before installation.
| System | Kind | Built for | Certified to | Certified for | Flow | Five years |
|---|---|---|---|---|---|---|
| A.O. Smith Whole House Sediment Filter, Valve-in-Head (AO-WH-PREV) | Sediment filter | City | NSF/ANSI 42 | Nominal Particulate Reduction, Class V | 6 gpm | $131 |
| A.O. Smith Whole House Central Water Filter (AO-WH-FILTER) | Carbon filter | City or well | NSF/ANSI 42 | Chlorine | 7 gpm | $350 |
| Aqua-Pure AP903 | Carbon filter | City or well | NSF/ANSI 42 | Chlorine | 20 gpm | No price |
| Aquasana HealthShield (WH-HS) | Carbon filter | City or well | NSF/ANSI 53, 401 | PFOA, PFOS, PFHxS, PFNA, Total trihalomethanes (TTHM) | 5.7 gpm | $4,864+ |
| A.O. Smith 40,000-Grain Water Softener (AO-WH-SOFT-400T) | Water softener | City or well | NSF/ANSI 44 | Hardness | 8 gpm | No price |
| Aquasana SimplySoft 40,000 Grain Softener (WH-SF40) | Water softener | City or well | NSF/ANSI 44 | Hardness | 11.02 gpm | $2,031 |
| VIQUA PRO10 UV System | UV disinfection | City or well | NSF/ANSI 55 | Disinfection Performance, Class A | 10 gpm | No price |
| Aquasana Rhino Whole House Water Filter (WH-1000) | Carbon filter | City | None found | Maker’s claims only | 7 gpm | $2,664 |
| iSpring WGB32B 3-Stage Whole House Water Filter | Carbon filter | City or well | None found | Maker’s claims only | 15 gpm | $1,651 |
| Aquasana Rhino Chloramines Whole House Water Filter (WH-1011) | Catalytic carbon filter | City | None found | Maker’s claims only | 7 gpm | $3,464 |
| SpringWell Whole House Water Filter System (CF1) | Catalytic carbon filter | City | None found | Maker’s claims only | 9 gpm | $1,547 |
| iSpring WGB32BM 3-Stage Whole House Iron Filter | Combination system | Well | None found | Maker’s claims only | 15 gpm | $1,976 |
| SpringWell Whole House Well Water Filter System (WS1) | Iron and sulfur filter | Well | None found | Maker’s claims only | 12 gpm | $2,625 |
| SpringWell Salt Based Water Softener System (SS1) | Water softener | City | None found | Maker’s claims only | 11 gpm | $1,890 |
| Aquasana Salt-Free Water Conditioner (WH-SFWC-S) | Salt-free conditioner | City or well | None found | Maker’s claims only | 7 gpm | $2,424 |
| SpringWell FutureSoft Salt-Free Water Conditioner (FS1) | Salt-free conditioner | City | None found | Maker’s claims only | 12 gpm | $2,100 |
| SpringWell UV Water Purification System, 15 gpm (SPRW-UV-15gpm) | UV disinfection | City or well | None found | Maker’s claims only | 15 gpm | $1,807 |
A plus sign means a part due within the five years has no published price, so the real total is higher. “None found” means TapBuff searched NSF, WQA and IAPMO listings and found nothing; each system’s page gives the date.
Compare with your plumber’s quoteWhat each kind does, and what certifies it
Sediment filter
Sand and grit filter
Traps sand, silt, loose scale, clay and other particles that make water cloudy. Cartridge units need new cartridges, while larger whole-house media units are backwashed, Penn State Extension says.
Not for
- Anything dissolved in the water. Nebraska Extension says sediment filters alone do not remove nitrate, heavy metals, pesticides or trihalomethanes.
- Germs. Nebraska Extension does not generally recommend cartridge sediment filters for removing microbes.
- Very fine particles. Nebraska Extension says some clay and very fine "flour sand" pass through many cartridge filters.
Look for
NSF/ANSI 42. Look for the NSF/ANSI 42 claim "Nominal Particulate Reduction," which NSF listings grade from Class I to Class VI. A particulate claim says nothing about lead, germs or chemicals.
Activated carbon filter
Whole-house carbon filter
Removes chlorine taste and odor and some organic chemicals as water passes through a bed of carbon. UGA Extension says new carbon breaks down chlorine within seconds.
Not for
- Hardness. UGA Extension says activated carbon does not remove hardness, bacteria, nitrate, fluoride or most metal ions.
- Chloramine, unless the listing shows a chloramine claim. NSF says chloramine is harder for treatment systems to reduce than chlorine.
- Lead from your home's own pipes. EPA says lead can enter water after a whole-house filter, so it points to a lead-certified filter at the tap.
- Germs. Penn State Extension says bacteria can multiply in a carbon filter, so water with bacteria needs disinfection.
- Hydrogen sulfide above about 1 ppm. Penn State Extension says plain activated carbon works only below about 1.0 mg/L.
Look for
NSF/ANSI 42. Look for the NSF/ANSI 42 claim "Chlorine Reduction" (WQA: "Aesthetic Chlorine"). Carbon can also hold NSF/ANSI 53 health claims. On Oct. 4, 2026, NSF and WQA together listed only a few whole-house products with VOC, PFOA or PFOS claims, and none with lead.
Catalytic carbon filter
Treated carbon filter
A treated carbon that traps hydrogen sulfide and then oxidizes it, so it handles far more than plain carbon. Penn State Extension says it needs at least 4.0 ppm of dissolved oxygen in the water and regular backwashing.
Not for
- Hardness, nitrate or most metals. UGA Extension says carbon does not remove them.
- Chloramine, unless the listing shows a chloramine claim. UGA Extension says carbon breaks down chloramine more slowly than chlorine.
- Lead from your home's own pipes. EPA says lead can enter water after a whole-house filter, so it points to a lead-certified filter at the tap.
- Germs. Penn State Extension says bacteria can multiply in carbon filters, so water with bacteria needs disinfection.
Look for
NSF/ANSI 42. For city water, look for the NSF/ANSI 42 claim "Chloramine Reduction" (WQA: "Aesthetic Chloramine"). A "Chlorine Reduction" claim does not cover chloramine. On Oct. 4, 2026, NSF listed no whole-house product with a chloramine claim, and WQA listed two from one maker.
Iron and sulfur filter
Oxidizing iron filter
Turns dissolved iron, manganese and hydrogen sulfide into solid particles, then traps them in a media bed that backwashes to a drain. Some use greensand renewed with potassium permanganate, and others add chlorine or air first.
Not for
- Hardness, which needs a softener. Penn State Extension lists oxidizing filters only for iron, manganese and hydrogen sulfide.
- Germs. It is not a disinfection system, and Penn State Extension recommends disinfecting water after aeration.
- Very high hydrogen sulfide. Penn State Extension says oxidizing filters handle up to about 2 to 3 ppm and points to chlorine or permanganate feed above 6 ppm.
Look for
NSF/ANSI 42. NSF lists iron and manganese as possible NSF/ANSI 42 claims, but its listing search showed no products with them on Oct. 4, 2026. WQA lists "Iron" and "Hydrogen Sulfide" claims under NSF/ANSI 42, seen only on whole-house systems from one maker.
Water softener
Ion exchange softener
Swaps calcium and magnesium for sodium or potassium on resin beads, then flushes the hardness down the drain with salt brine. It prevents scale but is not a drinking water filter.
Not for
- Lead, nitrate, bacteria, hydrogen sulfide, silt or pesticides. Nebraska Extension lists these among the things softening does not remove.
- PFAS or chlorine taste. NSF/ANSI 44 has no claims for them.
- Arsenic. Minnesota's health department says conventional softeners alone will not remove it.
- Iron that has already rusted. Minnesota's health department says iron or manganese exposed to air or chlorine can clog the resin.
- Protecting pipes. Minnesota's health department says softening can corrode pipes and raise lead and copper levels in the water.
Look for
NSF/ANSI 44. Look for the NSF/ANSI 44 claim "Hardness Reduction" (WQA: "Hardness"). Some softeners also list "Barium Reduction," "Radium 226/228 Reduction" or "Efficiency Rated." NSF/ANSI 44 covers only softeners regenerated with sodium or potassium chloride.
Salt-free conditioner
Scale control without salt
Tries to stop hardness minerals from forming hard scale, for example by turning them into tiny crystals that stay in the water. The minerals stay in the water, so the water is not softened.
Not for
- Removing hardness. WQA says these devices do not reduce total calcium or magnesium and are not proven to make soft water.
- Passing a hardness test as proof. WQA says some test methods may read lower because minerals turn into particles, while total calcium and magnesium stay the same.
- Water with iron, manganese or sediment. The University of Minnesota says crystallization systems need fairly clean water and may need a filter first.
- Any drinking water contaminant. The test protocols that exist for these devices measure scale only.
Look for
No NSF/ANSI standard. NSF/ANSI 44 is only for softeners regenerated with salt. IAPMO/ANSI Z601-2025, "Scale Reduction Devices," is an American National Standard for them. Germany's DVGW W 512 (1996) is withdrawn, and the publisher recommends DIN 3607-2 (May 2023) in its place. WQA/ASPE/ANSI S-803 is a sustainability standard, not a scale test.
Ultraviolet (UV) disinfection
UV light disinfection
Shines ultraviolet light on water as it flows past a lamp, which inactivates bacteria, viruses and cysts. It adds nothing to the water and leaves no disinfectant in the pipes after it.
Not for
- Chemicals such as lead, nitrate, arsenic or PFAS. NSF/ANSI 55 has no chemical reduction claims.
- Cloudy, iron-rich or hard water. Particles and scale shield germs from the light, so Virginia Extension and Connecticut's health department put UV last, after other treatment.
- Germs that get into the pipes after the unit. Penn State Extension says UV leaves no residual disinfectant.
- Heavily contaminated wells. Penn State Extension does not recommend UV above 1,000 total coliform or 100 fecal coliform colonies per 100 mL.
- Taste, odor or clarity. Connecticut's health department says UV does not improve them.
Look for
NSF/ANSI 55. For a well or any water that may carry germs, look for "Disinfection Performance, Class A." Class B is only for extra treatment of water that is already safe. WQA says Class A delivers at least 40 mJ/cm² and Class B delivers 16 mJ/cm².
On city water
Your utility already disinfects the water, with chlorine or with chloramine, and has to meet EPA’s limits. A whole-house carbon filter is mostly about the taste and smell of that disinfectant.
- Chloramine is its own claim. NSF says a system certified for chlorine is not necessarily effective on chloramine. On Oct. 4, 2026, NSF listed no whole-house system for chloramine, and WQA listed two, from one maker. More on chloramine.
- Health claims are rare. Whole-house carbon can be certified to NSF/ANSI 53, but on Oct. 4, 2026, only a handful of whole-house systems carried a VOC, PFOA or PFOS claim on any listing.
- Change it on time. Carbon strips out the disinfectant, and CDC says Legionella can grow in filters that are not properly maintained.
On a well
Nobody tests a private well but its owner. Start with a certified lab, then treat in order, so each step protects the next.
- 1Sediment. Grit first, so it doesn’t clog what follows.
- 2Iron and sulfur. Before the softener. Nebraska Extension says iron above 5 ppm or hydrogen sulfide cuts a softener’s effectiveness.
- 3Softener. If hardness is a nuisance. Minnesota’s health department calls it a personal choice, not a requirement.
- 4UV, last. Particles and scale shield germs from the light. For a well, look for NSF/ANSI 55 Class A.
Better handled at the tap
- Lead
EPA says water can pick up lead from your own pipes and solder after a whole-house filter. On Oct. 4, 2026, neither NSF nor WQA listed a single whole-house system for lead.
- Arsenic
Penn State Extension says arsenic is a problem only when swallowed, and reverse osmosis for it is usually an under-sink unit.
- Nitrate
Usually treated at one tap with reverse osmosis. Minnesota’s health department says not to give well water with nitrate to babies under six months, even after home treatment.