How to Maintain a Reverse Osmosis System (4 Essential Steps)

TL;DR: Change pre-filters every 6-12 months, replace the RO membrane every 2-3 years, sanitize the system annually, and check for leaks quarterly. Neglecting these steps cuts water quality and shortens system life.

_Last reviewed: July 2026 · 6 min read_

Reverse osmosis systems deliver some of the purest drinking water you can get at home, but they don't run maintenance-free. Landlords with RO units installed in rental properties or primary residences often skip filter changes until water tastes off or flow slows to a trickle. By then, the membrane may already be damaged and expensive to replace.

Okoniq Property Hub logs filter-change dates and membrane replacements so you never guess when the last service happened.

What filters does a reverse osmosis system use?

Most under-sink RO systems have three to five filter stages. The first stage is a sediment pre-filter that catches rust, sand, and particles down to 5 microns. The second is a carbon pre-filter that removes chlorine and volatile organic compounds. The third stage is the semi-permeable RO membrane itself, which blocks dissolved solids, heavy metals, and contaminants as small as 0.0001 microns. Some systems add a fourth carbon post-filter to polish taste before the faucet, and a fifth remineralization filter to add back calcium and magnesium.

Pre-filters protect the membrane. If they clog, sediment and chlorine reach the membrane and shorten its life from three years to under one. Replace sediment and carbon pre-filters every 6-12 months depending on your water quality. Homes on well water with high iron or sediment should change them closer to six months. City water with low turbidity can stretch to twelve.

The membrane is the workhorse and the expensive part — $50 to $150 depending on the model. It should last 2-3 years under normal residential use. If your total dissolved solids (TDS) meter shows output water creeping above 20 ppm when it used to read 10, the membrane is failing. Closing a seasonal home for winter without draining the system can freeze and crack the membrane, forcing early replacement.

How often should you sanitize the system?

Sanitize the entire RO system once a year. Bacteria and biofilm can grow inside the storage tank and tubing even when the membrane is filtering properly. Symptoms include a musty smell or slimy feel to the water.

To sanitize, turn off the feed water, remove the pre-filters, and pour a capful of unscented household bleach (5.25% sodium hypochlorite) into the first filter housing. Reassemble without filters, turn the water back on, and let the system run until you smell chlorine at the faucet. Close the faucet and let the bleach sit in the lines and tank for 30 minutes. Then drain the tank completely, install fresh pre-filters, and flush the system by filling and draining the tank twice. The third tank fill is safe to drink.

Some manufacturers sell citric acid sanitizing kits as an alternative to bleach. Follow the kit instructions, but the process is the same: flush the disinfectant through, let it dwell, then rinse thoroughly. Mark the date in Okoniq so you know when the next annual cycle is due.

If you also maintain a basement dehumidifier, coordinate the RO sanitization with your spring or fall whole-house maintenance sweep.

What maintenance does the storage tank need?

The pressurized storage tank under the sink holds 2-4 gallons of filtered water. It's a steel or composite bladder tank with an air chamber on one side and water on the other, separated by a rubber diaphragm. The air pressure pushes water to the faucet when you open it.

Over time, the air pressure drops. When it falls below 6-8 psi, the tank can't push water out efficiently and you'll get weak flow even with a new membrane. Check the tank pressure once a year. Turn off the feed water, close the tank's ball valve, open the faucet to drain pressure, then use a tire pressure gauge on the Schrader valve at the bottom of the tank (it looks like a bicycle valve). Add air with a bike pump or compressor until the gauge reads 7 psi for most systems. Consult your manual for the exact spec.

If the tank diaphragm ruptures, the air and water sides mix and you'll hear waterlogging or see water dribble from the air valve. Replace the tank — they cost $40 to $80 and last 5-10 years. A ruptured diaphragm can't be repaired in the field.

How do you check for leaks and maintain tubing?

Inspect the system quarterly. Look under the sink with a flashlight and check every push-fit connection and threaded joint. Common leak points are the membrane housing cap, the automatic shut-off valve, and the drain saddle on the sink's drainpipe. Tighten the housing by hand — never use pliers on plastic threads. If a push-fit connection leaks, cut 1/4 inch off the tubing end, make sure it's square, and reinsert it.

The plastic tubing is rated for 10-15 years but can crack if it's kinked, exposed to sunlight, or stressed by being too short. Replace any section that looks brittle or white at the bends. Use 1/4-inch John Guest or similar food-grade polyethylene tubing. The drain line clogs less often than AC condensate drain lines, but if you hear gurgling or see slow flushing during the rinse cycle, pull the line from the drain saddle and flush it with water.

Some systems include a pressure gauge on the feed line. If inlet pressure exceeds 80 psi, install a pressure reducer. High pressure can blow fittings and shorten membrane life. If your home has variable pressure or water hammer, a reducer is cheap insurance.

What should you log in a maintenance record?

Track every filter change, membrane replacement, sanitization, and pressure check with the date and the part number. If you manage multiple properties with RO systems, this record prevents guesswork when a tenant calls about slow water. Note the TDS reading before and after each membrane change so you can see performance trends.

For rentals, consider a service contract with a local water-treatment company that swaps filters on a schedule. The cost is $100 to $200 per year but removes the burden of remembering dates. If you self-maintain, set a recurring reminder in Okoniq six months out for pre-filters and 24 months for the membrane.

FAQ

How long does a reverse osmosis membrane last?

Two to three years under typical residential use. Homes with high sediment, hardness above 10 grains per gallon, or chlorine exposure will see shorter life. A TDS meter that shows output creeping above the membrane's rated rejection percentage signals it's time to replace.

Can I drink the water immediately after changing filters?

Flush the system first. After installing new pre-filters or a membrane, fill the storage tank, drain it completely, then fill it a second time. The first fill rinses carbon fines and preservatives. The second fill is safe to drink.

Why does my RO water taste flat or different after a new membrane?

The membrane strips dissolved minerals that give water taste. Some systems include a remineralization cartridge as the final stage. If yours doesn't, you can add one for $30 to $50. It reintroduces calcium and magnesium, improving taste and raising pH slightly.

How do I know if my pre-filters are clogged?

Water flow drops noticeably, the system takes much longer to refill the tank, or you hear the booster pump running constantly. Pull the sediment filter after six months and inspect it. If it's brown or packed with debris, it's done its job. Replace it before that debris reaches the membrane.

What's the white chalky buildup on the membrane housing?

Hard water scale. If your feed water has hardness above 7 grains per gallon, consider a water softener upstream of the RO or flush the membrane with citric acid solution every six months. Scale buildup chokes flow and makes the membrane work harder, shortening its life.

This is educational information, not plumbing or health advice. For questions about water quality, contact your local health department or a licensed water-treatment professional. Always follow manufacturer instructions for your specific RO model.