For the most part, reverse osmosis filters don’t require much maintenance. The most important maintenance task is to replace the filter cartridges after the prescribed period.
Other than that, the system usually chugs along just fine. But a few problems can still arise. They are usually issues that you can solve yourself with basic tools and easy-to-find parts.
This is a go-to troubleshooting guide for the most common issues with RO systems. We outline common problems, potential causes, and the best solution for each.
Note: For more specific instructions for troubleshooting and repairing your specific reverse osmosis filter, refer to your manual or contact the manufacturer.
If you haven’t yet bought a reverse osmosis system, use our in-depth RO filter buying guide to find the right one for your needs.
1. RO Water is Flowing Out in a Trickle
Reverse osmosis water doesn’t usually gush out like tap water. Because water passes slowly through the various filtration stages, it also flows out slowly from the faucet.
To check if your flow rate is within the normal range, let the water flow in a jug, bottle or any other container for exactly 60 seconds. Use the timer feature on your smartphone.
Measure the number of gallons collected in that one minute and compare it to the GPM (gallons per minute) figure from the manufacturer. If the manufacturer does not say what flow rate to expect, compare your figure to that of other customers (check customer reviews).
Some fast RO systems can produce up to 1 gallon per minute while others produce as little as 0.5 gallons per minute.
An easy way to increase the flow rate is to install an electric booster pump.
You can also install a non-electric permeate pump (cheaper and doesn’t require a power connection), but it won’t increase the flow rate as much as a booster pump will.
Sometimes, however, a low flow rate is not caused by the lack of a pump. If your GPM is lower than that of other users or the one stated by the manufacturer, there could be another issue.
Here are a couple of possible causes.
If the first one’s the issue, check if there’s a problem with your home’s plumbing that could be slowing down water pressure.
See if the problem is also affecting other faucets. If it is, there could be a shut-off valve that needs to be adjusted to increase water pressure.
A leak somewhere in the system can also cause a drop in your home’s water pressure.
The problem could also be your municipal water supply. There’s nothing you can do about that other than buying a booster pump to increase the pressure of water going into the RO system.
If your home’s water pressure is good, the problem is likely within the RO system. More specifically, the pressurized reserve tank.
It has either lost pressure or leaks. Here’s how to check if it has lost pressure and re-pressurize it.
How to Check RO Tank Pressure (and Re-Pressurize It)
If the water pressure starts to fall again, the tank may have a leaking bladder. You’ll have to buy a new reserve tank.
Note: Too much pressure in the tank can also reduce water flow since the tank can’t hold much water. If you get a reading above 7 psi on your pressure gauge, release some of the pressure.
If the tank is in good condition and your home has adequate water pressure, the other possible issue is clogged filters.
If the current filters are more than 6-12 months old, they may be clogging up and slowing down water flow.
Replace them and see if water pressure improves.
2. No Water
If the RO faucet is completely dry, not even a trickle, the first thing to check is whether all the valves are open.
Check the main feed valve as well as the tank valve.
If those are good, confirm that the tank is under the right amount of pressure. Lack of pressure or too much pressure could prevent RO water from flowing.
Clogged filters could also prevent the water from flowing. Replace them if necessary.
Also, make sure there are no curved lines.
If everything seems okay, check your home’s water pressure. A sudden drop off in water pressure can prevent water from passing through the RO system.
If it’s not a plumbing problem in your home, you may have to install a booster pump to increase water pressure.
If you find water has pooled on the floor under the sink, your RO system has a leak. Luckily, this is an easy problem to diagnose and solve.
Look for leaks around valves and connectors. These include the connectors at the filter inlets and outlets.
If the leak is coming from a quick connect fitting going into a filter or valve, check if the tubing is pushed in far enough. If it’s still leaking, order new quick connect fittings from the manufacturer such as this spring pack of 10.
If the leak is coming from one of the filters, it could also be a damaged O-ring.
Close the feed valve and drain the system by letting the RO faucet run until nothing comes out. Remove connections to the affected filter and unscrew it.
Inspect the O-rings for damage. If they are cracked or seem worn out, replace them.
If the leak is coming from the top of the reserve tank, the valve might be the source.
Shut off the water supply to the RO system and open the faucet to drain the tank. Disconnect the tubing leading to the tank and then unscrew the valve.
If there’s an O-ring, check whether it needs to be replaced. Also, check if the valve itself is cracked.
If everything seems okay, put everything back but use some plumber’s tape to provide extra leak protection.
If the leak is coming from your faucet, you likely have an air gap faucet. It leaks if the drain line is clogged.
Shut off water to the R O system and then remove the drain tube (usually colored black) that connects to the drainpipe.
Use a pipe cleaner to unclog any debris that may be blocking water flow. Reconnect the drain tube and open the feed valve. Check if the faucet is still leaking.
4. Noisy Drain
Some noise is common when the RO system is draining. It usually sounds like a gurgling noise.
The noise is especially noticeable when you first install the RO system or put in new filters. It’s caused by air being pushed out.
But if it persists for several days or the noise is louder than usual, check if there is an obstruction in the drain pipe.
Also, check the rest of the system to make sure everything is ok. A bent tube can restrict water flow and cause unusual noises.
5. Constant Draining
Your RO system should not always be draining water. It only drains water when it’s filling up the tank. Some of the water gets into the tank while reject water goes down the drain.
Sometimes, water will keep draining even after the tank is full, causing a lot of water wastage and creating a continuous gurgling noise.
There are three possible causes.
One, your tank is not pressurizing correctly. As water fills the tank, air pressure should increase steadily to 35-40 psi, which triggers a check valve that stops water flow into the tank. This also prevents water from draining.
If your tank doesn’t have enough pressure, the valve won’t work, and water will keep flowing in and down the drain.
Use the procedure we outlined above to check your reserve tank’s pressure and re-pressurize it.
The second possible problem is a faulty check valve. The check valve shuts off the water supply to the tank when it reaches a certain pressure, meaning it’s almost full.
Once you let out some of the water by opening the faucet, it opens to allow more water to flow in.
If the check valve is not functioning correctly, it will not stop water flow into the tank when it should. Thus, water will continuously flow down the drain.
The best solution is to replace the valve.
If your tank has the right pressure and your check valve is ok, another possible problem is the flow restrictor.
This is a small part that maintains high water pressure inside the RO membrane. Without it, there would be a lot of water wasted and very little water getting into the tank.
A faulty flow restrictor can allow water to drain unimpeded, resulting in a constant draining sound. Replacing it should solve the problem.
6. Water Tastes Bad
RO purified water has a ‘pure’ taste with no odors or tastes detectable. If your system has a remineralization stage, you’ll taste some earthiness from the minerals added back into the water.
But if your water has an unusual chemical or chlorine smell, that’s a problem. It means the filters are not working as they should.
Replace the filters immediately.
RO pre-filters are designed to last for 6-12 months. Leave them in for too long, and they get clogged and stop filtering water effectively.
This not only gives the water a bad taste, but it can also damage the chlorine membrane from exposure to chlorine and other chemicals.
Once you replace the pre-filters, you’ll notice a significant improvement in taste. But if the water still tastes bad, the problem is with the membrane.
Buy a new membrane and see if it improves the water quality.
A dirty RO system can also cause foul-tasting water. Sanitize the RO system every time you replace the filter to prevent a buildup of bacteria, mold, and other bad stuff.
RO water can also have an unusual taste if you haven’t used it in several days or weeks. If you’ve been away on vacation or travel, first flush the tank to get rid of the old water.
To do this, close the feed valve and then open the faucet to drain the tank. Open the valve to let the tank fill up again.
If the water still has an unusual taste, do a second flash.
7. Water Tastes Sour or Metallic
Metallic or sour-tasting water is a sign of low pH.
RO water is generally slightly acidic because it lacks mineral ions. If your tap water was already acidic, passing it through an RO system lowers the pH further, causing the metallic taste.
You can solve this by buying an RO system with a remineralization stage. These systems have a filter that adds some of the removed minerals back into the water to restore pH and taste.
But that would cost you the price of a full new RO system. An easier option is to buy a mineral filter and add it to your existing system.
There also other ways of re-mineralizing RO water without spending a lot of money or installing anything. We’ve outlined them in this blog post.
Once you increase your RO water’s pH, it should have a pleasant earthy taste.
8. Little or No Water from the Refrigerator Dispenser
If the water from the RO faucet is coming out fine, but there’s little or no RO water from the refrigerator dispenser, there are three possible problems.
One, the shut-off valve might be turned off, or it’s faulty. If it is damaged, you’ll need to replace it.
Two, the tubing taking water to the refrigerator is bent. That’s easy to fix once you find the kink.
Three, there’s some blockage somewhere in the system. It’s likely on the refrigerator water inlet screen. It might be clogged with scale. Clean the screen to unclog the water flow.
If you’ve connected your RO system to an icemaker and you are not getting any water, check the valve and see if the tubing is bent.
9. TDS Levels are Too High
A good quality reverse osmosis system reduces TDS levels by up to 99%. But if you are still getting high readings on your TDS meter, it’s a sign that your RO membrane is not working properly.
The likely issue is that the membrane is damaged. This happens when you don’t replace the pre-filters on time, and the membrane is exposed to chemicals like chlorine.
Too-high TDS levels can also result from a ruptured membrane, which can be caused by a faulty check valve.
The only solution is to replace the RO membrane and then measure TDS levels again.