Air injection, chemical injection, or a softener alone

When a private well stains fixtures or smells like rotten eggs, the equipment conversation is usually one of three approaches: air injection, a chemical injection of peroxide or chlorine, or a water softener asked to do a job it was not built for. This page is the difference. It is not a test of a brand.

What the iron is doing

Ferrous iron is dissolved in the water. A glass can look clear at the tap and then go yellow or orange as oxygen reaches it. That delayed stain is the usual story on toilets, tubs, and laundry. Ferric iron has already reacted with oxygen. It is a particle, and the water looks rusty immediately.

A lab report may say total iron, dissolved iron, or both. If you only have a total, ask the lab whether they filtered the sample. Dissolved iron can be oxidized and then filtered. Particles already in the water may need a sediment step so they do not pack the bed.

You can watch a glass for an hour as a clue. Clear, then orange, points toward ferrous iron. Orange from the first moment points toward ferric iron, or toward iron that oxidized in the pipes. Write down what you saw. Then ignore it as a buying tool until the lab report agrees. A glass is not a certified test.

Manganese and sulfide are separate lines

Manganese often leaves black or dark brown stains and can color the water. Hydrogen sulfide is a gas, and it smells like rotten eggs. A sheet that only publishes an iron number has not told you it will handle the other two. Reading the lab report keeps those lines from getting blended into "high minerals."

Air injection

An air-injection filter, also called an aeration or AIO system, exposes the water to oxygen. Many designs keep a pocket of air at the top of the tank. Dissolved ferrous iron reacts and becomes solid ferric iron. The media bed catches the solid. The same oxygen step is how these systems go after manganese and hydrogen sulfide, inside whatever limits the manufacturer prints. On a timer or a meter, the valve backwashes the trapped solids down a drain and refreshes the air.

That is the mechanism, not a review. It fails in ordinary ways:

• The lab pH is outside the operating range printed for that model. Oxidation is sensitive to pH. More media does not correct it.
• Iron, manganese, or hydrogen sulfide is above the printed limit.
• The well pump cannot supply the backwash flow, so the bed never really rinses.
• Iron bacteria leave a slime that coats the media.
• Tannins, the tea color some wells have, interfere with the oxidation the sheet assumed.

Air injection is the category to price when your numbers and your pH sit inside a published air-injection sheet, and when bacteria are not part of the report. SpringWell and SoftPro both sell this category for well water. US Water Systems sells it as well, alongside a chemical-feed line. Match the model, not the logo. The question list for those three is how to do that without a fake score.

Peroxide or chlorine injection

Chemical injection uses a metering pump to add an oxidant before the water spends a short time in contact and then passes through a filter bed. Hydrogen peroxide is the oxidant many well-water companies use when iron, manganese, or hydrogen sulfide run higher than their air systems claim, and when iron bacteria have been chewing up air-injection beds. Chlorine is the other common oxidant. Afterward, the solids have to be filtered out, and any leftover oxidant has to be handled the way that system was designed. Do not assume a peroxide feed and a chlorine feed leave the same residual.

This page does not give concentrations, pump settings, jug recipes, or contact times. Those numbers depend on your lab result, your flow, and the equipment manual. Get them from the manufacturer of the system or from a licensed water professional. A household bottle poured into a brine tank is not this design.

The trade is upkeep. You buy oxidant on a schedule, and you own a pump that can lose prime or clog. In exchange, you may get a category whose published limits cover a report that every air-injection sheet rejected. US Water Systems is one company that sells peroxide-injection iron and sulfur systems as well as air injection. Confirm which product page you are on.

A chemical feed is still not a fix for coliform bacteria, E. coli, nitrate, arsenic, or lead. Do not describe it that way to the household. If those lines are present, the health department comes before any jug of oxidant.

A softener used alone

A water softener is an ion-exchange tank. Resin swaps calcium and magnesium, the minerals that leave scale, for sodium or potassium. That is hardness treatment. It is not an iron filter.

Ferrous iron is dissolved, so a small amount can stick to resin. A normal regeneration does not always pull it back off. The bed fouls. You then own a softener that softens poorly and still does not keep up with the staining. Ferric iron is a particle. It can clog the resin rather than exchange onto it. Makers who allow any iron on a softener publish a ceiling, and that ceiling is usually far below a true iron-filter rating. If your iron is more than a trace, read that ceiling. Expect to put an iron filter ahead of the softener.

Hardness and iron often show up together. That is two jobs. Oxidize and filter the iron and the sulfur. Then, if you still want less scale, exchange the hardness. A combo price from a brand does not merge those jobs into the softener. The iron half still has to match the lab sheet.

pH and flow outrank the brand

Every serious air-injection sheet publishes a pH range. Compare your lab pH to it before you compare warranties. If you are outside the range, ask what pH equipment they put ahead of the filter and what pH that step is supposed to produce. Calcite and soda-ash feeds exist for that reason. This site is not going to tell you how to mix either one.

Flow is the other gate. Service flow is the treated water you can draw while people are in the showers. Backwash flow is the higher rate the tank wants when it cleans. Your well pump has to do both, and the drain has to accept the backwash. Cost and tank size stays with that problem. A bathroom count on a product label is the manufacturer's shortcut, not your measurement.

A way to sort the three

1. If the lab shows coliform, E. coli, nitrate, arsenic, or lead, stop. This choice is premature. Call the health department.
2. If iron bacteria are present, or slime and an oily film keep coming back, say so before anyone sells you air injection. Ask whether they want the well disinfected first, and whether they will stand behind an air system for that water. Chemical injection is often the category under discussion. Get the answer from the maker, not from an advertisement.
3. If the water is clear and then stains, pH is inside an air-injection range, and iron, manganese, and sulfide are all inside a published air-injection limit, price air injection.
4. If any of those contaminants sits above the air-injection limits you can actually find in print, price a chemical-injection system against the same report.
5. Add a softener only for hardness you still want to remove, and only inside the resin's published iron limit. Do not buy the softener as the iron filter.