Softener, filter, reverse osmosis or UV? Each treats something different. Here they are side by side, with the standard to check for each and how they fit together in a San Jose home.
Water Softener San Jose is an independent referral service, not an installer or plumber. When you send the form, your details are passed to an independent local water treatment pro, who can contact you and prepare a quote.
Your water is already treated: what home treatment adds
City water in San Jose comes from a water company that tests it and publishes the results in an annual water quality report. San Jose Water’s 2025 report, for example, notes that chlorine and chloramine, used to destroy disease-causing organisms, may be present in its water. Home treatment is about what you want beyond that: softer water, a different taste, or a specific contaminant reduced at your tap. Hardness, for example, has no health-based standard; San Jose Water says hard water does not pose a health risk.
The options at a glance
| System | What it does | Where it goes | Standard |
|---|---|---|---|
| Water softener | Removes the calcium and magnesium that cause hardness | Main line, every tap | NSF/ANSI 44 |
| Whole-house filter | Taste, odor, sediment or a named contaminant | Main line, every tap | NSF/ANSI 42, 53 or 401 |
| Tap or under-sink filter | Taste, odor or a named contaminant | One fixture | NSF/ANSI 42 or 53 |
| Reverse osmosis | Membrane treatment of drinking water | One fixture, such as the kitchen sink | NSF/ANSI 58 |
| Ultraviolet (UV) | UV light treatment | Main line or one fixture | NSF/ANSI 55, Class A or B |
Softening for hard water
Hardness in San Jose depends on the source. San Jose Water’s 2025 report gives averages of about 5.8 grains per gallon for Valley Water treated surface water, 9 for mountain surface water and 16.8 for groundwater. On the USGS scale those run from moderately hard to very hard. If scale, spots and soap scum bother you, a softener is the tool. See water softener installation in San Jose for sizing and the install, and water softener repair in San Jose if you already have one that has stopped working.
Filtering for taste, odor and specific contaminants
A filter is chosen for a problem. Ask first what you want to remove or reduce, then pick a unit certified to reduce it. For every tap in the house, see the whole house water filter in San Jose. For a broader guide to filters at one tap or the whole house, see water filtration in San Jose.
Reverse osmosis for drinking water
A point-of-use reverse osmosis system treats water at one fixture through a semi-permeable membrane. EPA says RO can potentially remove contaminants such as lead, VOCs, PFAS and arsenic, and that a typical system sends five gallons or more of reject water down the drain per gallon treated, while WaterSense labeled units send 2.3 gallons or less. See reverse osmosis in San Jose.
Ultraviolet treatment
UV systems treat water with ultraviolet light instead of passing it through a filter medium. NSF/ANSI 55 is the standard for them, in two classes, Class A and Class B. On city water, ask what a UV system is meant to treat in your supply before you buy one; on a private well, the test results guide the choice. Either way, ask which class a unit is certified to and what the maker says about lamps and upkeep.
What a good quote shows
Whatever the system, a written quote should let you compare it with another. Look for the exact make and model, what it is certified to reduce and under which standard, where it will go, how it will be bypassed for service, what upkeep the maker calls for, and every part of the price. If the quote is for a softener, it should name the hardness the system was sized for and where that figure came from.
Putting systems together
Systems can be combined. One pairing is a softener on the main line for the whole house and reverse osmosis at the kitchen sink. Another is a whole-house filter alongside a softener. When more than one system goes in, ask how each is bypassed for service, which goes first on the line, and whether both can be quoted on one visit.
Not sure which system you need? Send the form and an independent local pro can contact you about your water.
If your home is on a private well
Some homes draw water from a private well rather than a water company. EPA says private well owners are responsible for the safety of their water, and private wells are not regulated under the federal Safe Drinking Water Act. EPA and CDC advise testing a private well at least once a year for total coliform bacteria, nitrates, total dissolved solids and pH, and more often after problems nearby, after any part of the well is repaired or replaced, or if the water’s taste, color or smell changes. Use a state-certified laboratory. Treatment for a well is chosen from those results.
Before you choose
- Read your water provider’s annual water quality report.
- Note what you notice at the tap, and test if you want to know what reaches your own faucet.
- Decide one tap or the whole house.
- Ask what each system is certified to reduce, under which NSF/ANSI standard.
- Check with the City of San Jose permit center about any permit.
- Get every quote in writing.
Questions people ask
Is San Jose water treated before it reaches my home?
Your water company tests it and publishes the results in its annual water quality report, the place to read what was found in your supply. San Jose Water’s 2025 report notes that chlorine and chloramine, used to destroy disease-causing organisms, may be present in its water.
Do I need a softener or a filter?
A softener for hardness (scale, spots, soap that will not lather); a filter for taste, odor, sediment or a specific contaminant. Some homes have both.
Can I combine a softener and reverse osmosis?
Yes. They do different jobs: the softener treats the whole house for hardness, RO treats drinking water at one tap.