Start with the water problem, then compare five years of cost. A whole-house system treats water as it enters your home; an under-sink system treats the water at one tap. If only drinking and cooking water needs treatment, compare a suitable point-of-use option before paying to treat every tap. If the problem affects water use throughout the house, ask a qualified water professional to identify the treatment and coverage needed.
What to check before shopping
The CDC’s guide to home water filters recommends checking water quality and choosing a product for the specific substance you need to reduce. Public-water customers can start with the utility’s water quality report; if the concern is specific to your plumbing or a private well, ask the health department about testing and a certified lab. Taste or odor is not proof that water is safe. Ask for the exact model and the certification claim for your target substance. A softener’s hardness reduction does not establish that it removes germs or other contaminants.
A five-year comparison you can copy
Use the same price basis for both bids: installed equipment, replacement parts, scheduled service and any identified power or water costs. The values below are fictional and omit tax, financing and future price increases. They are not price ranges or evidence that the systems provide equivalent treatment.
| Cost item | Whole-house example | One-tap example |
|---|---|---|
| Installed price | $1,600 | $450 |
| Replacement filters | $120 per year | $95 per year |
| Scheduled service | $80 per year | $0 assumed |
| Five-year total | $2,600 | $925 |
The whole-house example is $1,675 more over five years. Compare that difference only if the two options meet your tested needs. If you need treatment at every tap, the one-tap system is not an equivalent substitute. If a quote lists a replacement interval in gallons, ask the installer to translate it into a practical schedule for your household. Treat unpriced work as unknown, not zero.
Put the same questions on both quote requests
Ask for a written installation scope, who handles permits if needed, expected flow for your household, the replacement part numbers, how to tell when a part needs service, and the warranty exclusions. Ask how the installer will verify the result at the taps that matter. If the unit removes a disinfectant from water entering the home, discuss the effect on the downstream plumbing and follow the manufacturer’s maintenance instructions. Follow any health department or utility advisory rather than assuming a household filter resolves it.
Sources and next steps: CDC: Home Water Treatment Systems; Homestria: Compare Contractor Quotes.