Guide · Updated 2026-08-30

Whole-house iron and sulfur filters

Air, chlorine, catalytic media, and carbon — compared as classes, then looked up by model in NSF’s database.

A “whole-house well system” ad is usually a photo of a tall tank and a claim about iron, sulfur, and manganese. The useful question is which chemical job the tank is built to do. Whole-house here means point-of-entry after the pressure tank: every tap, the toilet, the laundry. It does not mean a faucet pitcher. It does not mean a softener with a new decal.

EPA’s iron SMCL is 0.3 mg/L; manganese 0.05 mg/L; odor is an aesthetic secondary standard. USGS Circular 1332 says those aesthetic exceedances are common in domestic wells. Common is not the same as “one SKU fits the county.”

The classes

Air injection (oxidizing filter with a headspace of air)
A compressor or a venturi adds air. Iron, manganese, and some H2S oxidize. Media filters the particles. The unit backwashes. Good fit: moderate iron, some sulfur, pH in the media’s range, a well that can spare backwash gallons. Weak fit: iron bacteria slime, very high H2S, pH in the basement.

Manganese-dioxide / catalytic mineral beds
Greensand-type and newer MnO2 media catalyze oxidation if oxygen or an oxidant is present. Some need periodic regeneration with permanganate or chlorine; some want only air. Read the media sheet, not the brochure headline.

Catalytic carbon
Useful for low-to-moderate H2S and for polishing chlorine after a feed system. Carbon loads up on iron. A carbon tank as your only iron filter is how you buy a heavy black cylinder twice.

Chemical injection (chlorine or hydrogen peroxide) + contact + filter + polish
The grown-up class for high iron, serious sulfur, and bacterial slime after the well itself has been addressed. It needs a pump, a solution tank, contact time, and someone who will test residual. It is not “set and forget.” Peroxide avoids a chlorine taste but is not a toy.

Ozone
Effective oxidizer in competent hands. Also a way to spend a lot of money on a generator that sits offline. If you cannot name who services it, do not start here.

Softener
Not this class. See iron filter vs. water softener.

What “sized for a house” means

Ask for service flow in gallons per minute at your iron and sulfur numbers, not at zero. Peak morning use on a three-bath house can exceed 10–12 gpm. Undersize the bed and you get breakthrough: the first cup of coffee looks fine and the third shower stains.

Ask for backwash flow. Many MnO2 beds want more backwash than the well produces. Dealers then “turn down” backwash until the bed never lifts. The tank looks installed. The media cakes.

Ask about drain. Rusty backwash in a drywell next to the wellhead is a bad joke.

Order relative to everything else

After the pressure tank, the usual stack is:

1. Sediment if the water is sandy
2. Iron/sulfur oxidation and filtration
3. Neutralizer if pH still needs help and the iron plan allows it
4. Softener
5. Carbon polish if you chlorinate
6. UV last, and only on clear water

Details and exceptions: treatment order. UV on rusty water is a lamp behind a shade.

Bacteria is not a media upgrade

Minnesota Department of Health: iron bacteria clog and create habitat for other organisms; test coliform and nitrate; disinfection of the well may be needed and may not last. Penn State: sulfur bacteria and heater anodes are different H2S sources. A bigger whole-house tank does not replace a sanitary well cap or a pump job.

If a certified lab reports coliform, you are not in the filter-comparison chapter.

How to compare brands without a countdown list

1. Put iron, Mn, H2S (field), pH, hardness, and peak gpm on one line.
2. Pick a class from above.
3. Open manufacturer sites as catalogs, not rankings. SpringWell, US Water Systems, Pelican, Pentair, and Kinetico: official URLs, application pending. SoftPro: tracked catalog link (see disclosure):
   • SpringWell
   • SoftPro
   • US Water Systems
   • Pelican
   • Pentair (valves and residential systems)
   • Kinetico (dealer systems)
4. Search the exact model in NSF Certified Drinking Water Treatment Units.
5. Get two quotes that mention media type, bed depth, valve brand, and backwash gpm. If a quote mentions only “whole house well filter,” it is not a quote.

NGWA’s contractor lookup is for people who work on wells. Some also hang tanks. License still matters.

Maintenance is part of the class

• Air systems: check the air charge and the odor after a power outage.
• Chemical feed: refill, verify residual, replace tubing.
• Carbon: replace or rebed before it dumps what it held.
• Any backwashing tank: confirm the drain still runs and the valve still cycles. A valve that died in July will announce itself in October stains.

Write the install date on the tank with a marker. Future you is the next contractor.

What this page will not do

It will not rank SpringWell against SoftPro. It will not say a filter makes water “pure” or medically safer. Aesthetic SMCLs are about staining and smell. Health claims need health tests and a health department.

Bottom line

Whole-house iron/sulfur treatment is oxidation plus filtration, sized to the lab sheet and the well’s backwash. Carbon polishes. Softeners soften. Air, chlorine, peroxide, and ozone are tools in that class, not lifestyle brands. Look models up at NSF. If the toilet tank is slimy, start with the well.