Reverse osmosis maintenance comes down to one principle: the cheap cartridges in front exist to protect the expensive membrane behind them, so replacing prefilters on schedule is what makes the membrane last years. Add an annual sanitize, a storage tank pressure check, and attention to flow and taste, and an RO system stays boringly reliable for a long time.
The parts that wear, and why order matters
A typical system has three classes of consumable: sediment and carbon prefilters, the membrane itself, and a final polishing postfilter. The prefilters take the abuse, straining particles and stripping chlorine, and chlorine protection is not optional, because chlorine chemically degrades most membranes. Every month a spent carbon prefilter stays in service, the membrane behind it is being eaten. That is why the golden rule of RO maintenance is unglamorous: change the cheap cartridges on time and the expensive part largely takes care of itself.
A working schedule
Manufacturers print intervals for each cartridge, and those model-specific numbers beat any generic advice: heavy use and heavily loaded water shorten every interval. As a shape, prefilters and postfilters are routine annual-order items, while the membrane is a multi-year component whose life depends almost entirely on how faithfully the prefilters were changed. Vendors such as iSpring publish the full replacement schedule for each system on its product page, which makes it easy to put the dates in a calendar the day you install. The calendar, not memory, is the maintenance system.
The warning signs of an overdue system
RO systems fail politely, which is the danger. Slowing flow at the faucet points to clogged prefilters or a tired membrane. A return of chlorine or off tastes means the carbon stages are exhausted. Water that tastes flat but measures high in dissolved solids on a cheap TDS meter means the membrane is passing what it should reject. A tank that empties after one glass has usually lost its air charge. None of these announce themselves loudly; you notice them only if you know they are the symptoms, which is most of the argument for the calendar.
Sanitizing, tank checks and the annual ritual
Once a year, at a cartridge change, sanitize the system: with cartridges out, run a sanitizing solution through the housings and tank per your manual, flush thoroughly, then install the fresh cartridges. Check the storage tank's air charge with a pressure gauge at the valve stem while the tank is empty, and top it up with a hand pump if low. Inspect fittings for weeping and the drain saddle for slime. The whole ritual takes an evening and resets the system to day-one behavior; our whole house reverse osmosis system guide covers the larger version of the same routine.
Questions people ask about reverse osmosis maintenance
What happens if I never change my RO filters?
Flow slows, tastes return, and chlorine reaching the membrane degrades it, turning a routine cartridge cost into a membrane replacement. Neglect converts the cheapest maintenance into the most expensive.
How do I know when the membrane itself is due?
Rising dissolved solids in the treated water is the tell, and an inexpensive TDS meter makes it visible. When readings climb toward the untreated number despite fresh prefilters, the membrane is done.
Do I need to sanitize an RO system, or just change filters?
Both. Cartridge changes keep performance; an annual sanitize of housings, lines and tank keeps the clean side hygienic. Doing them together makes each an easy habit.
Why does my RO tank give only a glass or two of water?
Usually the tank's internal air charge is low, so it cannot push its stored water out. Check the charge with a pressure gauge with the tank empty and repressurize it with a hand pump.