Search "reverse osmosis worth it" on Reddit and you find years of threads across r/DIY, r/HomeImprovement, r/Frugal, and various regional communities. The conversation has shifted noticeably over the past few years: skepticism has largely given way to strong positive consensus, with a predictable cluster of specific objections that come up in nearly every thread. Here is what the discussion actually looks like, what the objections are, and my direct take on where the crowd gets it right.
For how RO works and what it removes, see Reverse Osmosis Systems Explained.
The Taste-Convert Theme
The single most consistent positive report in RO threads: taste. People who install under-sink reverse osmosis systems and return to share results describe the difference in their drinking water in terms that read almost uniformly as converts. The before-and-after contrast between Phoenix tap water (464–716 mg/L in total dissolved solids per the city's 2025 report, plus a chlorine disinfectant) and the 20–50 mg/L output of a quality RO system is significant enough that most first-time users describe it as immediately obvious.
The downstream behavior change comes up nearly as often as the taste itself: people stop buying bottled water within the first few weeks after installation. For households that have been buying cases of water or maintaining a bottled water delivery service, the elimination of that habit is cited as a quality-of-life improvement that was not fully anticipated before the install.
What to look for: Certification to NSF/ANSI 58, the standard for reverse osmosis drinking water systems. It verifies that a system actually reduces total dissolved solids and any other contaminants it claims to remove.
The Bottled Water Cost Math
Multiple Reddit threads include homeowners calculating their bottled water spending and comparing it against RO ownership costs. The math consistently favors RO when a household spends more than roughly $25–$40 per month on bottled water, a threshold that many Phoenix-area families of two or more people easily exceed, particularly those buying cases weekly or subscribing to delivery services.
A professionally installed under-sink RO system produces filtered water at a fraction of a cent per gallon once the equipment cost is amortized over its useful life. Filter maintenance (pre-filters every six to twelve months, membrane every two to three years) adds roughly $50–$150 per year in ongoing costs. Against $300–$600 or more in annual bottled water spending, the payback period is typically under three years for an actively bottled-water-buying household.
The secondary lifestyle benefits come up frequently in these discussions alongside the financial math: no more carrying cases from the car, no running out unexpectedly, no plastic to dispose of. These are not financial, but they are consistently cited as improvements people did not fully anticipate before installing.
The Two Real Objections
Two legitimate criticisms of reverse osmosis come up consistently across these discussions, and they deserve honest engagement rather than dismissal.
Objection 1: Wastewater Ratio
Standard RO systems produce roughly one gallon of filtered water for every three to four gallons they process. The remaining water is flushed as concentrate wastewater carrying the rejected minerals and contaminants. This is a real and meaningful consideration in a desert environment. Phoenix and surrounding cities face long-term water supply constraints from drought and Colorado River allocation pressures, and the wastewater ratio of a traditional RO system is a legitimate environmental concern, particularly for environmentally conscious households.
The relevant context: high-efficiency RO systems now achieve ratios much closer to 1:1, though they cost more upfront. For a household producing one to two gallons of drinking water daily at the kitchen tap, the absolute volume of additional water consumption is modest, a few gallons per day against typical household usage of 50–100+ gallons. Whether that trade-off is acceptable is a personal calculation, and one worth making explicitly rather than ignoring.
Objection 2: Mineral Removal
RO systems remove calcium and magnesium, the same minerals that create water hardness and scale. The concern raised in threads: is demineralized water problematic for long-term health? Are consumers missing important dietary minerals they would otherwise get from tap water?
This objection is more nuanced than either side of the debate usually admits. Most people get the bulk of their calcium and magnesium from food, not water. But a 2005 World Health Organization review raised real concerns about drinking fully demineralized water over the long term and recommended adding minerals back. The concern is strongest for people with restricted diets, but it is a reasonable question for anyone.
The practical answer is the alkaline remineralizing RO system: an additional filtration stage that adds calcium, magnesium, and trace minerals back into the water after the RO membrane and raises pH to 7.5–8.5. This directly addresses the mineral objection while preserving the full contaminant removal benefits of the RO process. It is what most quality installations now include as standard.
The research: The World Health Organization's 2005 report Nutrients in Drinking-Water examined long-term consumption of demineralized water and focused on how minerals should be added back. That is exactly what the remineralization stage in an alkaline RO system does. (WHO)
A Counterpoint Worth Hearing
If you live alone or with one other person and your primary concern is mild chlorine taste rather than high TDS, arsenic, nitrates, or PFAS exposure, a high-quality pitcher filter or countertop carbon block may give you most of the taste benefit at a fraction of the cost and without under-sink installation. An NSF-certified pitcher filter effectively removes chlorine taste and odor. It will not match RO for total dissolved solids, heavy metals, or PFAS, but for taste-only concerns at modest daily volumes, it is a legitimate starting point before committing to a full under-sink system. Know what you are actually trying to remove before deciding on the technology.
Expert Commentary: Peter Whalen, Founder, Whale Spout Water
I have installed a lot of RO systems across the Phoenix metro, and the before-and-after reaction is genuinely consistent. Almost everyone who installs one stops buying bottled water within the first month. That alone pays for the system in most cases, but it is not actually what I find most compelling about RO for Phoenix homeowners specifically.
What matters most in Phoenix: total dissolved solids. The City of Phoenix's 2025 Water Quality Report lists total dissolved solids of 464 to 716 mg/L, often above the EPA's 500 mg/L aesthetic guideline. That mineral load is the flat, salty taste people notice, and it's the one thing a pitcher filter can't touch. A pitcher's carbon handles the chlorine taste well; only the RO membrane brings dissolved solids down to the 20 to 50 mg/L range. If you've ever noticed that your tap water tastes "heavy" even through a filter, that's dissolved solids, and that's where RO earns its keep.
On the wastewater objection: it is real, and if you are environmentally motivated, ask specifically about high-efficiency systems. The per-day absolute volume is modest for a kitchen drinking tap, but it is not nothing in a water-constrained region. I recommend high-efficiency configurations to customers who raise this concern, and the price premium is reasonable.
On the mineral objection: I always include alkaline remineralization as part of a standard RO installation. It is a modest cost addition that adds calcium, magnesium, and trace minerals back into the output water and raises pH. The water tastes noticeably better than pure demineralized RO output: slightly fuller, less flat, and it eliminates the mineral-removal objection entirely. If you have encountered this concern and it has been keeping you from installing an RO system, a remineralizing system resolves it.
On the question of whether you need RO if you already have a softener: yes, for different reasons. The softener handles scale and hardness throughout the home. The RO handles drinking water purity, including dissolved solids, chlorine taste, nitrates, PFAS, and the small sodium addition from the softener. They are not redundant. The combination is what I recommend most often, and the all-in cost is still well under what a single Culligan installation typically runs.
About Whale Spout Water
We install 5-stage NSF-certified under-sink RO systems with alkaline remineralization for $899 fully installed: dedicated faucet, storage tank, and all fittings included. Many customers pair this with a whole-home softener or conditioner for complete water treatment throughout the home. Free 15-minute video consult to figure out the right combination for your situation. See pricing. Serving Phoenix, Scottsdale, Chandler, Gilbert, Mesa, Tempe, Glendale, Peoria, and the West Valley.