Buying guides
Start here if you are not sure what you need yet. These guides cover testing your water, reading the results, sizing a system to your house, and what installation and upkeep really cost.
For the science behind each problem, see our contaminant pages and treatment methods.
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How to remove PFAS from your water
Reverse osmosis and activated carbon remove PFAS; boiling does not. What NSF/ANSI 53 and 58 certify, why carbon struggles with short-chain PFAS, and costs.
Updated September 27, 2026
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How to test your well water
Test a private well every year for coliform bacteria, nitrate, pH and TDS at a state-certified lab. What else to add, what it costs, and how to read the results.
Updated September 27, 2026
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How much a whole house water filter costs
Whole house filters cost $500 to $3,000 to buy, $120 to $600 or more to install and $70 to $1,000 a year to run. Here are 10-year costs by system type.
Updated September 27, 2026
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What size whole house water filter you need
Size a whole house filter by peak flow: gpm by bathroom count, fixture flow rates, main line size, pressure drop and carbon contact time, with worked examples.
Updated September 27, 2026
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Iron in well water: what it is and how to remove it
Iron above 0.3 mg/L stains fixtures. How to tell ferrous, ferric and bacterial iron apart, and which fix fits: softener, air injection, oxidizing media or chlorine.
Updated September 27, 2026
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Why your well water smells like rotten eggs, and how to fix it
Rotten egg smell is hydrogen sulfide. Hot taps only usually means the water heater anode; all taps means the well. Fixes by level: carbon, air injection, chlorine.
Updated September 27, 2026
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Chloramine vs chlorine: which is in your tap water and why it matters
How to tell whether your utility uses chlorine or chloramine, why chloramine needs catalytic carbon and longer contact time, and what it means for dialysis and fish.
Updated September 27, 2026
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Salt-free vs salt water softener
A salt softener removes hardness; a salt-free conditioner only changes how it scales. How each is tested, hardness limits, sodium added, costs and when each fits.
Updated September 27, 2026