You might avoid reverse osmosis (RO) water because the process removes calcium, magnesium and other dissolved minerals, can produce flat-tasting water, sends a reject stream to the drain and requires ongoing maintenance. These are genuine drawbacks, but properly treated RO water is not generally considered unhealthy for healthy people with an adequate diet.
Main disadvantages
- Mineral removal: RO produces low-mineral water by removing dissolved calcium and magnesium along with unwanted substances. Food is generally the main source of these minerals, although drinking water can contribute varying amounts (WHO).
- Taste: Removing minerals can make water taste flat. An optional remineralisation stage may improve flavour by adding selected minerals after treatment.
- Wastewater: RO divides incoming water into treated water and a concentrated reject stream. The amount sent to the drain varies with the system, water pressure, membrane condition and efficiency. Check the model’s water-efficiency specifications rather than relying on a universal ratio (US EPA WaterSense).
- Cost and upkeep: RO systems need cartridge changes, eventual membrane replacement and periodic servicing. Follow the manufacturer’s schedule, which will vary by system and water use.
- Hygiene: Cartridges, housings, storage tanks and taps must be maintained and sanitised as directed. Neglected maintenance can reduce treatment performance and allow hygiene problems to develop (CDC).
Is RO water unhealthy?
Mineral removal alone does not make RO water unhealthy for most people. Claims that it inherently causes dehydration, strips minerals from the body or creates electrolyte deficiency are not supported by strong public-health evidence.
RO water can have lower pH and buffering capacity, but this does not make the body dangerously acidic. The body regulates blood pH, and WHO does not set a health-based drinking-water guideline value for pH (WHO). People with restricted diets, malabsorption or clinician-managed electrolyte requirements should seek individual medical or dietary advice.
When RO may be unnecessary
RO may be unnecessary if there is no verified water-quality issue requiring broad removal of dissolved substances. For chlorine taste or odour concerns, a certified carbon filter may be sufficient. If testing identifies a particular contaminant, choose a system independently certified to reduce it, then compare water use and servicing requirements.
Under NSW regulations, all fixed drinking water filtration installations must comply with AS/NZS 3500.1 (the national water services standard governing certified WaterMark fittings, backflow prevention, and pressure limiting to safeguard household potable water supplies) under Building Commission NSW Contractor Licence 305428C and Qualified Supervisor oversight.
Fixed Today is the trusted plumbing team Sydney households have relied on and returned to for over 15 years for honest filtration advice. When you call, our team asks a couple of screening questions about your under-sink space, water pressure, benchtop material (such as stone or laminate), and existing drainage connections so our service vehicle arrives equipped with suitable brackets, pressure-limiting valves, and drain saddles. If you are weighing RO against a simpler multi-stage carbon filter, contact our licensed Sydney water filter team. We walk you through a clear task breakdown of the installation steps, providing transparent upfront pricing and a $0 call-out on approved work.