Reading the color
Orange and rusty red is iron. Brown, gray brown and black is manganese. Around here most wells that have one have some of the other, so a lot of bathrooms show both: an orange ring in the tub and a black ring in the toilet.
The two stain differently. Iron gives you that classic rusty streak under the faucet, an orange stripe where the toilet fills, and dingy orange laundry that gets worse with every wash. Manganese shows up as black specks in the aerator screen and the dishwasher, dark smudges on white porcelain, and a black slick in the toilet bowl below the water line. Manganese stains at one sixth the concentration of iron, they're harder to scrub off, and they get blamed on mold more often than anything else in a well water house.
Neither one is visible in a glass at the tap when it first comes out. Both are dissolved, and both are colorless in that state. What you're looking at in the tub is what happens after the water meets oxygen at the faucet, chlorine bleach in the wash, or the inside of a 120 degree water heater. That's why the stains build where water sits and dries, and why the heater tends to be full of sludge on a bad well.
Clear water iron or red water iron: the twenty minute test
Fill a clear glass at a cold tap that runs raw water, an outside hose bib is ideal, and set it on the counter for twenty minutes. Don't touch it. Then look.
If the water came out of the tap clear and the glass now has an orange tint with rusty sediment settled on the bottom, you have clear water iron, the dissolved ferrous form. It oxidized in the glass while you waited. If the water came out already orange or cloudy, you have red water iron, the ferric form, meaning it oxidized somewhere before it reached you.
That difference decides the equipment. Clear water iron is in solution, so a plain sediment filter has nothing to catch. It has to be oxidized first and then filtered, which is what every real iron system does. Red water iron is already a particle, so filtration alone can catch it, but the more interesting question is why it oxidized upstream. Air getting into the system, surface water reaching the well, or an iron bacteria colony are the three usual answers, and each of those is worth chasing on its own.
One more thing the test rules out. If the rusty water only appears on the first draw in the morning and runs clear after thirty seconds, that isn't the well. That's corrosion inside old galvanized supply piping in the house, and no filter on the well line will change it.
The numbers where staining starts
Iron stains at about 0.3 mg/L. Manganese stains at about 0.05 mg/L. Those are the federal secondary standards, and secondary means aesthetic: they exist because of stains, taste, odor and color, not because of illness, and they aren't enforceable on a private well. A well right at 0.3 mg/L iron tastes fine and leaves a ring you notice after a month. At 1 to 3 mg/L you're scrubbing. Above 5 mg/L you're losing the fight daily and the water heater is filling with sediment.
Manganese is the one to look at twice. Beyond the staining threshold there's a health based guidance level about six times higher, in the neighborhood of 0.3 mg/L for lifetime exposure, and infants are the sensitive group because a baby's body takes up more manganese and clears it more slowly than an adult's. If you mix formula with well water, you should know your manganese number, not guess at it from the color of the toilet. Water at 0.4 or 0.5 mg/L looks only mildly dingy and is well past the guidance level.
Aesthetic also doesn't mean harmless to the house. Iron plugs aerators and shower heads, coats the inside of a water heater and steals its efficiency, fouls softener resin, plates out inside pressure tanks and drop pipe, and feeds bacteria. The staining is the part you see. The plumbing damage is the part that costs money.
The slime in the toilet tank is a different problem
Take the lid off the toilet tank and look at the walls and the flapper. If you find a reddish brown slime, stringy and gelatinous, the way the inside of a neglected drain feels, sometimes with an oily looking rainbow sheen sitting on the water and a swampy or musty smell, that's iron bacteria. It's a living colony, not a mineral deposit, and it needs a different fix.
Iron bacteria feed on dissolved iron and build a slime sheath around themselves. They aren't a pathogen and they won't make you sick, but they clog well screens, drop pipe, pressure tanks, cartridge filters and softener beds, they throw off water tests, and they produce sulfide smells as a bonus. They also reseed. Put a new filter on a well with an active colony and it plugs in a few months, and people blame the filter.
The fix starts with shock chlorination of the well and the whole plumbing system, sometimes with physical cleaning of the casing, and sometimes it takes more than one round. If the slime keeps coming back, continuous chlorine injection is what finally holds it. Clean the biology out first, then size the filter. Doing it in the other order is money spent twice.
What actually removes iron and manganese
Every system that genuinely removes them does two things in order: oxidize the dissolved metal into a solid particle, then filter that particle out. The differences are all in how the oxidation happens.
An air injection oxidizing filter is the common answer in these towns. One tank carries a pocket of compressed air above a bed of catalytic media. Water passes through the air, the iron and manganese oxidize, the media catches them, and the tank backwashes itself to drain in the middle of the night. No chemicals to buy. It handles roughly up to 10 mg/L of iron and a milligram or two of manganese if the pH cooperates. It is a meaningful install, sized to your iron numbers and your plumbing.
Manganese greensand is the older approach and still a good one, especially with iron, manganese and sulfur together. The media is coated in manganese oxide and gets regenerated with potassium permanganate, which means a solution tank somebody has to keep filled. Newer catalytic media do similar work without the permanganate as long as there's enough oxidant in the water. For heavy iron, an active bacterial colony, or all of the above at once, chlorine injection into a contact tank followed by a backwashing filter is the highest capacity setup and the one with the most upkeep.
Now the softener question, because it's the piece most people get wrong. A softener does remove iron by ion exchange, and on a well with clear water iron under about 1 mg/L, sometimes 2 or 3 with iron fighting salt and religious maintenance, it's enough. Above that it fails, and it fails in an expensive way. Iron oxidizes inside the resin bed, coats the beads, and the softener slowly loses capacity until you have hard water and orange water at the same time, plus resin that needs replacing. Any ferric iron or iron bacteria will foul it faster. A softener is a hardness appliance that tolerates a small iron load. When you need both, the iron filter goes in first and the softener goes after it.
Sequestering is the honest stopgap. A small pump feeds polyphosphate into the line, which binds the iron and manganese and keeps them in solution so they flow through the house without precipitating. Nothing is removed, and it quits in hot water, because heat breaks the bond and dumps the iron right into the water heater. At low levels, on a rental, or on a well you're already planning to replace, it buys time cheaply. It is not a treatment system.
Getting the stains out, and testing before you buy
Don't reach for chlorine bleach. Bleach is an oxidizer, and oxidizing iron is exactly what turns it into a stain in the first place. Bleach on a rust stain darkens it and sets it into the porcelain or the fabric. The same goes for most all purpose bathroom sprays that contain it.
Use an acid instead. Oxalic acid or a citric acid based rust remover lifts iron off porcelain, tile and glass, and it's what the products sold specifically as rust stain removers are built around. Test it on a hidden corner before you use it on a colored fixture or a specialty finish, because acid takes the shine off some of them. For laundry, a rust remover made for fabric, then rewash with no detergent and no bleach, and keep the load out of the dryer until the stain is gone, because dryer heat sets it permanently. Wiping fixtures dry after use slows the whole cycle down.
Then get the water tested before you shop. Sizing depends on the iron number, the manganese number, the pH, whether the iron is ferrous or ferric, whether iron bacteria are present, hardness, and your well's yield, because a backwashing filter needs a certain flow to lift its bed and a low yield fractured rock well can't always deliver it. Test the raw untreated water at the wellhead or a hose bib ahead of any existing equipment, because a sample pulled after a softener tells you nothing about what's coming out of the ground. Call 973-853-1550 and we'll take a sample and size the system off numbers instead of off the color of your tub.