Reverse osmosis
Reverse Osmosis Systems for Better Drinking Water
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A reverse osmosis system pushes water through a fine membrane to remove most dissolved minerals and many contaminants, usually at one kitchen faucet. Angi lists under-sink RO in Phoenix at $1,100 to $1,800 installed. It is a common upgrade for Valley homeowners who don't love the taste of their tap water, and we match you with up to 5 licensed local companies for free quotes.
- Under-sink RO for drinking and cooking water
- Hookups for fridge and ice maker lines
- Whole-home RO for special cases
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What is a reverse osmosis system and what does it remove?
Reverse osmosis (RO) pushes water through a membrane with extremely small pores. Most dissolved minerals and many contaminants are left behind and rinsed away, while the treated water collects in a small storage tank or flows straight to a dedicated faucet. Most home systems also include sediment and carbon prefilters to protect the membrane and improve taste.
According to University of Arizona Cooperative Extension, RO is used to reduce total dissolved solids (TDS) and may reduce arsenic, lead and many organic chemicals. It is not effective for dissolved gases like radon or for some pesticides and volatile organic chemicals, and it may need pretreatment for sediment. Look for certification to NSF/ANSI 58, the standard for point-of-use RO systems: TDS reduction is its required claim, while arsenic, lead and nitrate reduction are optional claims that must be listed for the specific model.
Why reverse osmosis is popular in the Phoenix area
Valley city water meets drinking water standards, but some people don't like its taste. Dissolved minerals are one reason. The City of Phoenix's 2025 report lists total dissolved solids of 464 to 716 ppm, against a non-health secondary guideline of 500 ppm.
Tempe's water FAQ notes that Salt River water tends to run higher in dissolved solids and chlorides. See the full numbers on our Phoenix water softener page.
Hardness is also high. Phoenix reports 10 to 17.6 grains per gallon, and other cities are similar; see our Phoenix water hardness guide. A softener deals with scale, but it doesn't make water taste better and it adds sodium or potassium. RO reduces those at the kitchen tap.
RO and a water softener are a common pairing. The softener protects the whole house; RO handles the water you drink and cook with. University of Arizona Extension notes RO may need pretreatment, and in hard water a softener ahead of RO is a common way to provide it.
Types of reverse osmosis systems: under-sink, tankless and whole-home
| Type | Where it goes | Notes |
|---|---|---|
| Under-sink RO with tank | Kitchen sink cabinet | The classic setup. A small tank stores filtered water for its own faucet. |
| Tankless under-sink RO | Kitchen sink cabinet | Smaller footprint and faster flow; usually needs an electrical outlet. |
| Remineralizing RO | Kitchen sink cabinet | Adds a stage that puts a small amount of minerals back for taste. |
| Whole-home RO | Garage or utility area | Treats all water in the house. Large, costly and usually needs pretreatment and storage; best for special water problems. |
Most homeowners only need RO at the kitchen sink. Many installers can also run a line to the refrigerator's water dispenser and ice maker. Homes on well-heavy supplies, such as Queen Creek, often add RO for taste. Live in Mesa? See our reverse osmosis guide for Mesa, which uses the city's 2025 report. To see how RO compares with a softener, a conditioner and a whole-house filter, use our water treatment decision matrix.
How much does a reverse osmosis system cost?
| System | Typical range | Source |
|---|---|---|
| Point-of-use (under-sink) RO, Phoenix | $1,100 to $1,800 | Angi (Phoenix) |
| Point-of-use RO, national | $1,500 to $1,800 | HomeAdvisor |
| RO systems, general range | $1,000 to $4,800 | HomeAdvisor filtration guide |
| Whole-home RO, Phoenix | $4,750 to $12,000 | Angi (Phoenix) |
Typical ranges only, not quotes. Your matched pros set the actual price.
Ongoing costs include replacement prefilters, carbon filters and, less often, the membrane. Ask each company for its filter change schedule and parts prices so you can compare the true cost over several years. See the water softener cost guide for related numbers.
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Get My Free QuotesWhat to ask before you buy an RO system
- Which contaminants is the system certified to reduce, and to what standard? (University of Arizona Extension advises checking with the manufacturer for targeted contaminants and removal rates.)
- Is the system certified by NSF or the Water Quality Association for the claims being made? (University of Nebraska-Lincoln Extension notes home treatment equipment is largely self-regulated, so independent certification is a useful check.)
- How many stages does it have, and what does each one do?
- How often do filters and the membrane need changing, and what do they cost?
- How much water does it send to the drain for each gallon it produces?
- Does it need a new hole in the countertop or sink for the faucet?
- Can it connect to the fridge and ice maker?
- Is the installation and labor covered by a warranty?
If you are also dealing with scale or chlorine taste throughout the house, look at water softener installation or whole-house water filtration alongside RO.
Reverse osmosis installation: what to expect
What the installer connects
An under-sink system connects to the cold water line, a drain connection under the sink and a dedicated faucet. The installer flushes the system and checks for leaks. Tankless models may need an outlet in the cabinet. Running a line to the fridge involves tubing through cabinets or the floor, which the installer can assess on site.
How to prepare for the visit
Before the visit, clear out the cabinet under the kitchen sink and note whether you have a garbage disposal, since that affects where the drain connection goes. If your counters are stone or quartz, ask whether the faucet can use an existing sprayer or soap dispenser hole. After installation, the first tank of water is usually flushed, so expect to wait a few hours for full output.
Who does the work: in Arizona, the Registrar of Contractors' R-54 classification covers water conditioning equipment and its related piping, and licensed plumbers also install RO. Ask for the company's license number and check it at azroc.gov. We only send requests to companies that give us an active Arizona ROC license number and proof of liability insurance.
Related services and guides
Reverse osmosis FAQs
Does reverse osmosis remove hardness?
At the faucet it serves, yes. The RO membrane removes most dissolved minerals, including calcium and magnesium. But a standard under-sink system only treats water at that one tap, so it won't protect your shower, water heater or appliances from scale. For whole-house hardness you still need a softener or conditioner.
Do I need RO if I already have a water softener?
It depends on what bothers you. A softener removes hardness but adds sodium or potassium and doesn't improve the taste of mineral-heavy water much. If you want better-tasting drinking water or want to reduce dissolved solids, RO at the kitchen sink is the usual next step. Many Valley homes have both.
Does reverse osmosis waste water?
RO systems send part of the incoming water to the drain to carry away what the membrane rejects. The amount varies by system design, water pressure and pretreatment. Ask installers for the drain ratio of the specific model they quote, since newer and higher-efficiency units vary widely.
Is RO water safe to drink without minerals?
RO water is widely used for drinking and cooking. Some people prefer the taste of a system with a remineralization stage, which adds a small amount of minerals back. If you have a specific health concern, ask your doctor.
How often do RO filters need changing?
Prefilters and carbon filters are changed more often than the membrane. The exact schedule depends on the system, your water and how much you use. Hard, mineral-heavy water like much of the Valley's can shorten membrane life, which is one reason RO is often paired with a softener.
Can an RO system connect to my refrigerator?
Usually, yes. Installers run small tubing from the RO system to the fridge water line and ice maker, typically through cabinets or along the wall behind them. The length and path of that run affect labor, so mention the fridge when you request a quote. Also ask whether the system produces enough water for both the faucet and the ice maker.
Phoenix-area cities we serve
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Get My Free QuotesSources
- University of Arizona Cooperative Extension AZ1498: Home Water Treatment Options
- City of Phoenix 2025 Water Quality Report
- City of Tempe Water FAQ
- Angi: Water Softener Installation Cost in Phoenix, AZ
- HomeAdvisor: Water Softener Installation Cost
- HomeAdvisor: Home Water Filtration System Cost
- University of Nebraska-Lincoln Extension G1491: Drinking Water Treatment: Water Softening (Ion Exchange)
- University of Nebraska-Lincoln Extension G2275: Drinking Water Treatment: Water Softening
- Ariz. Admin. Code R4-9-103 (Residential contractor classifications, incl. R-54)
- NSF: NSF/ANSI 58 Reverse Osmosis Drinking Water Treatment Systems
Last updated October 2026.