Best Water Filter for Well Water: Test First, Then Buy

You need six results. Iron in ppm, manganese in ppm, hydrogen sulfide or a sulfur smell, total coliform and E. coli, hardness in grains per gallon, and pH. Sediment you can see for yourself.

A lab test beats test strips for iron and manganese, because the system you buy is rated in exact ppm. A strip that reads 'some iron' cannot tell you if you need a softener ($500 to $1,000) or a $3,395 peroxide system.

Bacteria is a separate quick test. Run it every year and after any flood, pump repair or change in taste. Order both kits now and you will have numbers to shop with in about a week.

Sand, grit or cloudy water: a spin-down sediment prefilter, under $100. It goes first in every system.

Iron under 1 ppm, no smell: a metered softener with a monthly resin cleaner does the job alone. Skip the iron filter.

Iron 1 to 7 ppm, or a mild sulfur smell up to 8 ppm: the SpringWell WS1 air-injection filter, with a softener behind it if the water is hard.

Iron above 7 ppm, or a strong sulfur smell up to 30 ppm: the Matrixx inFusion peroxide system.

Manganese with black or brown stains: both the WS1 and inFusion are rated to 1 ppm. Above that, take the lab report to a water treatment dealer.

Coliform or E. coli: shock chlorinate the well, then add a UV system as the last stage.

Hardness over about 7 gpg: a salt-based softener after the iron filter. Salt-free conditioners do not work on wells with iron.

pH under about 6.5: ask the manufacturer about a neutralizer ahead of the filter, because acidic water slows iron oxidation and corrodes plumbing.

Every well system should start with a sediment prefilter. Sand and grit wear out valve seals, clog iron filter media and pack the top of a softener's resin bed. A screen at under $100 protects $2,000 of equipment.

A spin-down filter uses a reusable mesh screen you flush with a valve at the bottom, so there are no cartridges to buy. Open the valve every week or two and watch the grit go out.

This is where the money goes, and the lab number makes the choice for you. Air injection handles most wells. Peroxide handles the hard cases.

Air-injection filters like the SpringWell WS1 hold a pocket of air at the top of the tank. Water passing through it oxidizes dissolved iron, manganese and hydrogen sulfide into particles, and a media bed traps them. The filter backwashes the particles to drain every few days. You need a drain line and a 120V outlet, and there is nothing to refill.

Peroxide systems like the Matrixx inFusion inject hydrogen peroxide, a much stronger oxidizer, so they handle 20 ppm iron and 30 ppm hydrogen sulfide. You refill the solution tank, so plan the floor space.

Flow is the spec people miss. The WS1 delivers 12 GPM, enough for 1 to 4 bathrooms. The inFusion delivers 15 GPM. In a filter and softener chain, the slower stage sets the flow for the whole house.

Most wells are hard as well as iron-heavy. Once the iron filter is in place, size the softener on hardness alone, and it lasts far longer because no iron fouls the resin.

Under 1 ppm iron, you can skip the iron filter and let a softener take the iron. Set the valve to compensated hardness, which is hardness in gpg plus 4 times the iron in ppm, and add resin cleaner monthly. Our water softener sizer does this math for you.

If the bacteria test comes back positive, shock chlorinate the well first and retest. A one-time contamination after a flood or a pump repair often clears up.

If it keeps coming back, add a UV system as the very last stage, after the softener. UV lamps only work on clear water. UV makers typically want iron under 0.3 ppm and low hardness, so the iron filter and softener have to go in first. Size the UV to the same GPM as the rest of the chain.

The whole-house filter and softener fix iron, smell and scale. They do not remove nitrate, arsenic or dissolved salts, which are common well problems that show up on the lab test. An under-sink reverse osmosis system does, for the water you drink and cook with.

Put it after the softener. Softened water protects the RO membrane from scale, and the RO takes back out the sodium the softener adds. A 50 GPD unit with a 4 gallon tank covers a family's drinking and cooking water.

Well, pressure tank, sediment prefilter, iron filter, softener, UV, then the house. Get the order wrong and the softener catches the iron you paid to remove.

Running costs are small. A softener valve draws about 5 W. Salt for a family of four on 15 gpg water runs about $100 to $150 a year. An air-injection backwash uses 50 to 100 gallons every few days. The peroxide system adds roughly $100 to $200 a year in solution. Run the water softener sizer with your lab numbers to size each stage.