Water Filtration in Santa Monica

Why is Santa Monica's water different from the rest of the Westside?

Because the city treats most of its own water. Santa Monica gets up to 75% of its supply from local groundwater wells in the city and in West Los Angeles. That water goes through the Arcadia Water Treatment Plant, which removes iron and manganese, filters it, and softens it with reverse osmosis before it is disinfected. The city's report says Santa Monica is the first in the nation to use flow reversal reverse osmosis to soften its groundwater.

The rest of the supply is purchased from the Metropolitan Water District, and imported water is generally harder than the softened local water. How much of each reaches your tap changes with the year and the season, which is one reason we test at your tap instead of relying on any single number.

The practical result: a whole-home softener is rarely the first thing a Santa Monica home needs. The city has already done a good part of that job.

What do people in Santa Monica notice in their water?

Taste and smell, mostly. The city disinfects its water, and its 2025 report lists total chlorine and chloramines at a citywide average of 1.80 ppm. That residual is what keeps the water clean in the pipes, and it is also what some people taste in a glass of water or smell in a hot shower.

In older apartment buildings and houses, the building's own plumbing matters as much as the city water. Old supply lines can add rust or sediment that the city's treatment never saw. That shows up as tinted water after the taps sit overnight.

What should a Santa Monica home put in first?

For a house, start with carbon. A whole-home catalytic carbon system on the main line takes the disinfectant taste and smell out of every tap and shower. Add an under-sink reverse osmosis system for purified drinking and cooking water at the kitchen sink.

Consider a softener only if you have a scale problem the city's softening is not solving, such as a test at your own hose bib that reads well above the city figure or a water heater that keeps filling with sediment. Our comparison of softeners, salt-free systems and carbon explains why we put it second here.

What can condo and apartment residents in Santa Monica install?

Most Santa Monica residents rent or own a condo, and that changes what is possible. Without your own main line, whole-home treatment is out, but drinking water and shower water are not.

An under-sink RO system is the strongest option for a condo kitchen. It needs a small drain connection and usually a faucet hole, so check your CC&Rs and ask the HOA before anyone drills a countertop or touches shared plumbing. Renters can use a countertop RO unit or a faucet-mount filter with no plumbing changes, or an under-sink unit with the landlord's permission. A shower filter rated for chloramine helps in the bathroom. Our condo and apartment guide covers the HOA questions in detail.

What does an install look like in a Santa Monica house?

In most Santa Monica houses and duplexes the main line comes in at the front, and the meter, shutoff and hose bib are close together. A carbon system goes on the main right after the shutoff, in the garage if there is room or outside on a pad with a cover. It needs no drain and no power.

We test your water and look at the condition of the supply pipe first. If the pipe is the source of the discoloration, we tell you that before you spend money on a filter.