Water Education
Reverse Osmosis Maintenance: A Simple Owner’s Guide
How a home RO system works and the maintenance it needs: prefilters, membrane, postfilter, and tank. Sourced from WQA.
A reverse osmosis (RO) system under the sink is a dependable source of drinking and cooking water, as long as it gets regular care. Here is how it works and what to keep up with.
How RO works
WQA describes RO as a process where water and contaminants are separated by passing through a thin semipermeable membrane. Pressure forces water through the membrane and leaves contaminants behind (WQA, RO Fact Sheet). It is called reverse osmosis because pressure pushes water in the opposite direction from natural osmosis (WQA FAQs).
What is inside a typical system
According to WQA, a typical RO system has a prefilter to capture larger particles, chlorine, and other substances; a semipermeable membrane that captures more contaminants; an activated carbon filter that removes residual taste, odor, and some organic contaminants; and a storage tank to hold treated water (WQA FAQs).
Most home RO systems are point-of-use units under the sink. WQA notes they usually produce about 3 to 10 gallons a day, which is why they serve a kitchen or bathroom tap instead of the whole house (WQA FAQs).
The maintenance it needs
WQA is plain about it: like any filter technology, RO systems require regular maintenance, including periodically replacing the prefilters, postfilters, and membrane modules (WQA FAQs).
Prefilters
Prefilters protect the membrane from sediment and chlorine. Replace prefilters on your manual’s schedule.
Membrane
The membrane does the main work. Its life depends on your water and use. Signs it is due: slower flow at the faucet, or a change in taste.
Postfilter
The carbon postfilter polishes taste and odor as water leaves the tank. Change it with the prefilters unless your manual says otherwise.
Storage tank
The tank holds air pressure that pushes water to the faucet. If flow is weak even with new filters, contact support.
Sanitizing
Sanitize the system and tank when you change filters, following your manual.
Is RO water safe to drink?
WQA states that drinking low-TDS water such as RO water does not pose health concerns for healthy people, because the body maintains its own mineral balance and food is the main source of nutrients (WQA FAQs).
A simple yearly routine
Pick one date each year, such as the start of spring, and do the whole job at once: shut off the feed valve and close the tank valve, relieve pressure at the faucet, replace the prefilters and postfilter, sanitize per your manual, check the tank air charge, and flush the system before drinking. Write the date on the housing. If the membrane is due, replace it the same day. Keeping it to one routine makes it much harder to forget.
Get the most from your system
Mark your filter change date on the housing or in your calendar.
Keep the feed water treated.
Look for systems certified to NSF/ANSI 58 and WQA S-101 when buying or replacing (WQA).
If something seems off, send a support request with your model and serial number.
Keep a spare set of prefilters on hand so a change never waits on shipping, and store them sealed in a cool, dry place. When you call for help, have your model, serial number, and the date of your last filter change ready; it makes troubleshooting much faster.
Sources
Water Quality Association, Reverse Osmosis Fact Sheet (wqa.org/resources/reverse-osmosis-ro/)
Water Quality Association, FAQs (find.wqa.org/learn-about-water/faqs)
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