Water filtration in San Diego: choosing the right system

Water Softener San Diego is an independent referral service, not an installer, plumber or equipment seller. When you send the form, your details are passed to an independent local water treatment pro, who can contact you and prepare a quote.

Start with the contaminant, not the product

Choosing home water treatment starts with one simple question: what contaminant do you want to remove or reduce? Then select a unit certified by NSF, Underwriters Laboratories or the Water Quality Association to remove that contaminant, and make sure the unit you are considering is certified for that specific one. That is a simple defense against buying a filter that does not do the job you bought it for.

For a San Diego home on city water, the reasons to look at filtration include these:

• Taste and odor, such as the taste of the disinfectant the water system uses
• A specific contaminant you have read about, such as lead from old plumbing or PFAS
• Drinking and cooking water you want filtered further at the kitchen tap
• Hardness, which is not a filtration job at all but a softener’s

The standards to look for

NSF/ANSI standards describe what a home water treatment product has been tested to do. A label that says only “NSF certified” tells you little; the standard number and the contaminants listed under it tell you what you are buying.

Standard	What it covers
NSF/ANSI 42	Aesthetic effects such as chlorine, taste and odor
NSF/ANSI 53	Health effects such as lead
NSF/ANSI 58	Reverse osmosis drinking water treatment systems
NSF/ANSI 55	Ultraviolet systems, Class A and Class B
NSF/ANSI 401	Incidental contaminants
NSF/ANSI 44	Residential water softeners (hardness, not filtration)

Ask an installer which standard each part of a proposed system is certified to, and for which contaminants. If a claim is made for a contaminant, the certification should name it.

Point of use or point of entry

Filtration systems sit in one of two places. A point-of-use system treats water at one fixture: a filter on a faucet, a pitcher, or an under-sink unit feeding the kitchen tap. A point-of-entry system treats all the water where it enters the house, so every tap, shower and appliance gets the same water.

	Point of use	Point of entry
Where it goes	Under the sink or at one tap	On the main line into the house
What it treats	Drinking and cooking water	Every tap and shower
Examples	Under-sink filter, reverse osmosis	Whole-house filter, softener
Good for	Water you drink	Taste and odor at every tap

For filtered water at every tap, see the whole house water filter page. For the kitchen tap alone, an under-sink filter or reverse osmosis is the place to look.

Reverse osmosis at the kitchen tap

EPA’s WaterSense program describes reverse osmosis as the process by which pressure forces water through a semi-permeable membrane, making treated water and reject water. A point-of-use RO system is connected to a single fixture, such as under the kitchen sink. EPA says RO systems can potentially remove contaminants such as lead, volatile organic compounds, PFAS, arsenic, bacteria and viruses. The standard to look for is NSF/ANSI 58.

RO uses water. EPA says a typical point-of-use RO system sends five gallons or more of reject water down the drain for every gallon of treated water, and some inefficient units send up to 10. WaterSense labeled systems must send 2.3 gallons or less per gallon treated. Ask the installer for the figure on any unit they propose. More on the reverse osmosis page.

PFAS: where the rules stand

EPA’s final rule set enforceable limits of 4.0 parts per trillion for two PFAS, PFOA and PFOS, in public drinking water. On May 18, 2026, EPA proposed two changes: one would keep the PFOA and PFOS limits but let water systems request two more years, to 2031, to comply; the other would rescind the limits for PFHxS, PFNA, HFPO-DA (GenX) and the mixture hazard index. Those are proposals, not final rules.

If PFAS is your reason for filtering, read what your water provider reports, and ask any installer which standard the proposed system is certified to for PFAS reduction. Reverse osmosis is one of the technologies EPA names as able to potentially remove PFAS.

Filtration and softening are different jobs

The City of San Diego says its water typically averages about 16 grains per gallon of hardness. A filter does not soften that water: calcium and magnesium are dissolved minerals, and the equipment that removes them for the whole house is a softener, covered by NSF/ANSI 44. In a San Diego home that wants both, a softener on the main line and a filter or RO for drinking water is one way to set it up. Ask the installer about the order of equipment on the line; it depends on what each part is meant to do.

Taste, color and the secondary standards

EPA keeps a list of secondary standards for contaminants that affect taste, color and odor rather than health. They are guidelines, and EPA does not enforce them. A few useful ones: total dissolved solids at 500 mg/L, linked to deposits, colored water, staining and a salty taste; chloride at 250 mg/L, linked to a salty taste; and a pH range of 6.5 to 8.5. If your water tastes or looks off, a water test against these guidelines tells a pro what a filter should target.

Read the city’s report first

The City of San Diego publishes an annual Drinking Water Quality Report, also called the Consumer Confidence Report, and issues the report for the previous year by July 1. If you are on city water, it is the place to start: it is the city’s own account of its water. If you are in Chula Vista, La Mesa, El Cajon or Poway, your water provider publishes its own report. See San Diego tap water for how to read it.

Pitchers and faucet filters

The smallest filters are pitchers and filters that fit on a faucet. They are point-of-use filters like any other, and the same rule applies: check the standard and the contaminants listed under it. A pitcher certified to NSF/ANSI 42 for chlorine taste and odor does a different job from one certified to NSF/ANSI 53 for lead.

Questions to ask an installer

• Which contaminants is this system certified to reduce, and under which NSF/ANSI standard?
• Is it point of use or point of entry, and why that for my home?
• Where will it go, and does it need a drain or power?
• How much water does it send to the drain, if it is RO?
• What upkeep does it need, and what does the maker’s schedule say about cartridges?
• Does it work with a softener, and in what order on the line?

What affects the quote

This site prints no prices. A quote for filtration depends on whether it is one tap or the whole house, the number of stages, whether RO needs a drain connection and its own faucet, the room under the sink, and replacement cartridges on the maker’s schedule. Ask for the cartridge schedule in writing so you can compare the running costs, not only the first bill. For a broader plan that includes softening and well water, see water treatment.

Questions people ask