Reverse Osmosis Systems: 11 Common Problems and Troubleshooting

by Jay | Updated on July 26th, 2022

Reverse osmosis filter systems effectively clean the water that gets into your homes. While, for the most part, it does not need a lot of maintenance, replacing the filter cartridges is vital to its functionality.


Other than that, there are some issues commonly raised by users, and we’re here to lay them out for you and give you tips on how you could fix them. 

Of course, you should first check the user manual that came with your unit in case of problems. If that doesn’t address it, you may check this article!

Reverse Osmosis

Reverse Osmosis (RO) utilizes a technology that eradicates most of the contaminants present in your home water by having it pushed and forced under pressure through a semipermeable membrane.

It utilizes a high-pressure pump to raise the pressure on the side of the salt of the RO and push the water through the semipermeable membrane. This removes up to 95-99% of the total dissolved solids.

Generally, the salt concentration of the feed water dictates the amount of pressure requirement. The more concentrated the water is, the more pressure is required for the osmotic pressure to be overcome. 

Permeate water is desalinated water that’s demineralized or deionized. On the other hand, the reject or concentrate stream is the water stream that holds concentrated contaminants that did not make it through the RO membrane.

Ro Membrane 1

Once enough pressure is generated to overcome the osmotic pressure, the feed water enters the RO membrane.

The water molecules then go through the semipermeable membrane, but contaminants and salts won’t make it through and are then discharged through the reject stream. This reject stream then goes to the drain or, in some cases, can be taken back into the feed water supply as a take on recycling. 

Key components of an RO system

Filters

  • Prefilters: protect from sediment and chlorine as they can clog the flow restrictor and destroy the membrane via oxidation.
  • Post filters: allows water to pass through carbon before making it out of your faucet or appliances.

Membrane

This membrane, as discussed, relies on pressure. Therefore, eradicating contaminants will not be enough without generating enough pressure. 

Flow restrictor

This creates resistance which provides a driving force on the membrane while simultaneously and efficiently metering the water flow rate to the drain. Its size depends on the membrane output rating and should be accurate. Otherwise, membrane output will be disrupted.

Check valve

This component is located at the membrane permeate outlet, which protects the membrane from back pressure. However, it also activates the ASO valve by letting pressure build while filling the tank. 

Automatic shut-off (ASO) valve

This valve functions to monitor feed and tank pressures. In events when the tank pressure is already at ⅔ of the line pressure, this valve closes and stops the water from flowing.

Storage tank

This storage tank used in RO systems is called pressure or hydro-pneumatic tank. It houses two chambers: one for air and another for water. An expansion of the separating diaphragm into the air side increases the pressure on that side as the tank fills with water.

Drain saddle

The drain carries the contaminants in the opposite direction from the permeate. This saddle connects the waterline from the air gap faucet and the sink drain line.

Air gap

This is for backflow prevention to avoid drain or sewage water backing up into the clean and drinking water supply.

Feed pressure

This pressure should be enough to keep the system’s performance at its best.

Troubleshooting tips

1. RO water flowing out in a small stream

While RO water doesn’t flow as strongly as tap water, it should not be in a trickle. A quick way to check if your flow rate is normal is to get a jug and let water flow to it for exactly 60 seconds.

Then, measure the water collected in gallons and compare it to the GPM (gallons per minute) figure. This is typically from the manufacturer. If your manufacturer does not offer this, compare it with other customers. RO systems can go as much as 1 gallon per minute, while others can be as low as 0.5. 

What you can do

  • Install an electric booster pump
  • Install a non-electric permeate pump (cheaper but less flow rate boost)

If these don’t fix the problem, the problem might be deeper. Either your home’s water pressure is low, or your pressurized tank may have an underlying issue.

For low-pressure water, you may call in for some plumbing help to check for things like some leakage. The RO system may be at fault if your water pressure is normal. To check for lost pressure and how to re-pressurize it if needed:

  1. Turn off the valve feeding water to the RO system.
  2. Open the RO faucet and let it run until no water is coming to drain it.
  3. Close the valve found at the tank top area.
  4. Disconnect the line leading into the tank.
  5. Access the pressure valve by opening the cap at the bottom of the tank.
  6. Check the air pressure in the tank using a pressure gauge. For a 4-gallon tank, it should be about 5 psi.
  7. If it’s lower than that, you’ll have to re-pressurize by adding more pressure using a bicycle pump. Remember not to use an air compressor as this may damage the bladder due to the over-pressurizing.
  8. Reconnect the lines and open the feed valves and the tank.
  9. Time to check the pressure of the water!

If the pressure is still off after this, your RO may have a leaking bladder issue, and you’ll have no choice but to buy a reserve tank. However, it’s also worth noting that too much pressure can decrease water flow.

If you get a reading more than 7 psi, you’ll have to release some of the pressure. Another thing worth looking into is clogged filters! Make sure to change your filters as needed.

2. No water

If there’s no water, you must check the main feed and tank valves. If they look good, check the pressure next because too low or too high of a pressure can stop the water from flowing. Clogged filters can also be the culprit. If all these look good, go and check your home’s water pressure. In some cases, you’d have to install a booster pump to help with the flow rate. 

3. Leakage

If you see water pooling on the floor just beneath the sink, it’s most likely that your RO is suffering from a leakage. Now look for the source of the leak and if it’s from a quick connect fitting going into a filter or valve, try to see if the tubing is placed far enough. If that fails, it’s time to order one from the manufacturer. 

It can also damage the O-ring. To confirm, close the feed valve and let the RO faucet run to drain the system. Then, take the connections out and unscrew so you can inspect the O-rings. Replace them if they look damaged or if they come with cracks. 

Now, if the leak is from the top of the reserve tank, the culprit might be the valve. Do the same thing as instructed with O-ring inspection but check for the valve this time. If despite your efforts to check everything still looks good, take everything back to where they were and utilize a plumber’s tape for that extra leak protection.

4. Noisy drain

A draining RO system will typically sound like a gurgling noise, especially when your RO system is newly installed or if the filters are new. This is created by air pushed out. However, if this persists for days, there might be some obstruction in the drain pipe. 

5. Constant draining

Your RO should drain water when the tank is being filled up to drain the rejected water. Some of the reasons can be:

  • The tank is not pressurizing correctly (in this case, re-pressurize it!)
  • Faulty check valve

6. Foul taste and odor

These are the common reasons for foul taste and odor:

  • Dirty filters
  • Sanitation issues
  • Membrane failure
  • Hydrogen sulfide or methane from the well water
  • Unused or stagnant water for an extended period of time allowing bacteria to thrive (flush the system after being idle for a while!)

7. Metallic or sour taste 

This is a sign of a low pH water. While RO water is already slightly acidic, tap water that’s already acidic to begin with might come out too acidic after getting through the RO.

A way around this is to opt for an RO system with a remineralization stage so the removed minerals can be infused back in to restore the pH level and get rid of the metallic taste. If this is too expensive for you, you can buy a mineral filter and install it to your system.

8. Lack or completely no water from the refrigerator dispenser

There are three possible reasons that can cause the lack of water from the refrigerator dispenser given that the RO faucet is coming out fine:

  • Faulty or turned off shut-off valve (replace it or turn it on!)
  • Bent tubing connecting the RO to the refrigerator
  • Blockage in the system

9. TDS levels too high

If your TDS meter is giving you a high reading, your RO membrane may not be working properly. More often than not, this is a damaged membrane caused by untimely replacement of pre-filters, exposing the water to chlorine and other chemicals. This problem can also be due to a faulty check valve rupturing the membrane. Replace the RO membrane in this case!

10. Cloudy ice cubes

This is caused by air bubbles in the water when the RO filter is new or newly replaced. This typically goes away after some time. However, cloudy ice cubes can also result from TDS being too high, and you will need a replacement of your RO membrane.

11. A running system without stopping

This occurs once the shut-off valve doesn’t close properly or if you have a broken check valve. This can also be caused by wrong membrane installation. To check, you have to measure the storage tank pressure, which should be 35-40 psi. If not, you might need some replacing.

Last words

We have broken down the most common issues you can encounter with your RO. If you look closely, a lot of these problems can be prevented by regular and proper maintenance. In the long run, proper maintenance will prevent these problems and always give you the best water supply experience. An RO system can be quite an investment, but it truly is worth it!

Jay

Self assessed Germaphobe, specializing in everything water, water filters, health and nutrition. Diagnosed with Type 2 Diabetes, I've acquired immense amount of knowledge when it comes to natural, biology, and everything about human anatomy.