Well water problems come in combinations, and each stage of a well system fixes specific things. Buying a filter before you have a lab test is the most common and most expensive mistake. Start with a certified lab test, then pick only the stages your results call for.
Match the problem to the stage
- Sand, silt, cloudiness: a sediment filter, usually 5 to 20 microns. Cheap cartridges, changed every few months. Almost every well system starts here because it protects everything downstream.
- Orange stains, metallic taste (iron), black stains (manganese), rotten-egg smell (hydrogen sulfide): an air-injection or oxidizing-media filter. See the iron and sulfur guide.
- Scale and spotting (hardness): a water softener. It also removes small amounts of dissolved iron.
- Taste, odor, some chemicals: carbon. Useful after the other stages, not a fix for bacteria, arsenic or nitrate.
- Coliform bacteria: shock chlorinate and fix the source first. If bacteria keep coming back, add a UV system as the last stage.
- Arsenic, nitrate, uranium: reverse osmosis at the kitchen tap is the usual answer, because you only need to treat the water you drink and cook with. Whole-house systems for these exist but cost far more.
The order matters
A typical full system runs: sediment, then iron and sulfur, then softener, then carbon, then UV, with reverse osmosis at the kitchen sink. UV only works on clear water; iron, hardness and sediment coat the lamp sleeve and let bacteria through, which is why it goes last.
Sizing
- Flow rate. The system must keep up with your peak demand, typically 8 to 15 gallons per minute for a house with two bathrooms. An undersized filter means a weak shower.
- Pipe size. Match the system's ports to your main line (usually 3/4 or 1 inch).
- Lab numbers. Iron filters, softeners and UV units each have limits for iron, manganese, hardness and hydrogen sulfide. Give the installer or the manufacturer your actual results.
Cartridge systems or backwashing tanks?
Cartridge housings are inexpensive and DIY-friendly, but cartridges clog fast on wells with iron or heavy sediment. Backwashing tanks cost more and need a drain and power, but clean themselves and last for years. Wells with more than a trace of iron usually end up with a backwashing tank.
Get quotes when
You need more than two stages, iron or sulfur treatment, or a softener plumbed in. Ask each installer which lab results the system is sized for, what maintenance costs per year, and whether a follow-up test is included.