What’s wrong with your water? Start with the symptom.
Nine results this page covers, what each one actually means, and which ones this site already has a tested system for. No test in hand yet? Start here. Already have a number? Skip to reading it.
Staining, a smell, a scale buildup on your fixtures, or a number on a lab report: each one points to a different category of treatment, and guessing wrong wastes money on a system that was never going to fix the problem you actually have. This page is the starting map for Silo 1 of this site: pick the symptom that matches what you are seeing, or jump straight to a number if you already have one.
Roundup sites rank products against each other without ever diagnosing what is actually wrong first. This site does the diagnosis first, then names the category of system that treats it, and the specific product only where one exists on this site.
A lab report or a city water quality report already has the numbers. This page is for when you only have a symptom.
Hardness (scale, soap scum)
Dissolved calcium and magnesium. USGS classifies water as hard above 121 mg/L as calcium carbonate, roughly 7 grains per gallon, with scale buildup, reduced soap effectiveness, and spotting as the practical effects rather than a health concern. Ion-exchange softening is the standard fix.
Orange or reddish staining (iron)
Iron’s EPA secondary standard is 0.3 mg/L. Staining is orange to reddish-brown, with a metallic taste at higher concentrations. An oxidizing filter is the standard whole-house fix above a few mg/L.
Black staining (manganese)
Manganese’s secondary standard is a stricter 0.05 mg/L, and EPA also carries a separate Health Advisory at 0.3 mg/L for chronic exposure, worth taking seriously in a household that mixes infant formula with tap water. Same oxidizing-filter category as iron, at a higher required threshold.
Rotten-egg smell
Hydrogen sulfide gas, and it has three unrelated causes: the water heater, sulfur bacteria, or gas dissolved in the groundwater itself. Only one of the three is a whole-house filtration problem. Read the full diagnostic →
Corrosive or acidic water (low pH)
EPA’s secondary standard sets a healthy range of 6.5 to 8.5. Below that range, water actively leaches metal, including lead and copper, out of your own household plumbing. An acid-neutralizing filter is the standard fix. No system on this site addresses pH yet.
Tea- or yellow-tinted water (color, tannins)
Organic tannins leaching from decaying vegetation or peat, usually harmless to drink. EPA’s secondary standard for color is 15 units. Anion-exchange resin or oxidation are the standard categories. No system on this site targets tannins yet.
Arsenic
An enforceable federal Maximum Contaminant Level of 10 parts per billion, tied to cancer and organ risk from chronic exposure. Not removed by a standard softener or an oxidizing filter; needs reverse osmosis, activated alumina, or arsenic-rated anion exchange. No system on this site addresses arsenic.
Nitrate
An enforceable federal Maximum Contaminant Level of 10 mg/L as nitrogen, tied specifically to methemoglobinemia (“blue baby syndrome”) in infants under six months. Needs reverse osmosis, nitrate-selective anion exchange, or distillation. No system on this site addresses nitrate.
Coliform bacteria present
A pathogen indicator, and the one result here that means act now rather than research. UV disinfection is the standard ongoing safeguard; shock chlorination can address a one-time event but often needs repeating. Contact a licensed well contractor or your local health department.
Why diagnose by symptom first
A system sized against a guess is the single most common way this kind of purchase goes wrong. Hardness and iron are frequently both present in the same well, and each is treated as its own line item rather than assumed to be covered by whichever system you buy first. Working from what you are actually seeing, smelling, or tasting narrows the category of fix before you ever look at a product.
Some of the results above already have a specific system on this site; several do not, and this page says so directly rather than pointing you at something that will not work. Where a category has no product here yet, the entry above still names the right category to shop for.
Already tested your water? Read the number instead
If you are holding a lab report or your city’s annual water quality report, you do not need to work from a symptom at all. Our guide to reading a water test maps each number on that report directly to a treatment category, with the same sourcing standard as this page.
And if the symptom is specifically a rotten-egg smell, the cause has three unrelated explanations with three different fixes, only one of which is a whole-house filtration problem. The full diagnostic is here, including how to tell the three apart from your own taps in about five minutes.
I have more than one of these symptoms at once. Do I need more than one system?
Often, yes. Hardness and iron in particular travel together constantly, and each is treated on its own merits rather than assumed to be solved by whichever system you buy first. Read each symptom against the category it maps to rather than assuming one purchase covers everything.
What is the difference between a secondary standard and an enforceable limit?
An enforceable Maximum Contaminant Level, like the ones for arsenic and nitrate, has a specific health basis and legal force for public water systems. A secondary standard, like the ones for iron, manganese, pH, and color, is aesthetic guidance the EPA does not enforce. Manganese sits in both categories at once, an aesthetic standard and a separate, non-enforceable Health Advisory for chronic exposure.
My city water report already lists most of these numbers. Do I still need my own test?
A Consumer Confidence Report describes water as it leaves the treatment plant, not necessarily what reaches your tap after your own household plumbing, which is where issues like lead from old fixtures or corrosion from low pH actually originate. It is a useful starting point, not a replacement for testing your own water if something seems off.
None of these symptoms match what I’m seeing. Now what?
Not every water problem has a visible symptom, and not every symptom is covered by this page yet. A full lab panel from a state-certified laboratory is the reliable way to find a problem that has no obvious sign, and it is worth doing on a private well even with no symptoms present at all.
Disclosure: this page contains affiliate links, and we may earn a commission if you buy through them, at no extra cost to you. Our recommendations are based on each system’s published specifications and the problem it is built to solve, not on commission.