Reverse Osmosis Troubleshooting: Problems, Solutions & How to Repair

Author: Rory Mullan - Published: 2021/07/23 - Updated: 2023/01/05

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Reverse osmosis may be considered the best method to purify water, but the filtration systems come with their own set of unique problems. Some issues are insignificant and can be fixed in a jiffy, while others require professional assistance.

Today, we shall go through the most common issues faced by RO filtration system owners and how to troubleshoot them.

Without further delay, let’s jump right in.

So, here is our reverse osmosis troubleshooting guide!

Reverse Osmosis Troubleshooting Overview: Most Common System Problems and Solutions

IssuePotential CauseFix
RO System Drains ConstantlyLow Storage Tank PressureRepressurize
Damaged Air BladderReplace Tank
Broken ASO ValveReplace
Broken Check ValveReplace
Low Feed Water PressureIncrease Pressure or Use Pump
Faulty InstallationReinstall
Worn Out RO MembraneReplace
Worn Out Flow RestrictorReplace
Storage Tank Does Not Fill UpTank Pressure Too HighRelease Pressure
Low Feed Water PressureIncrease Pressure or Use Pump
Worn Out RO MembraneReplace
Worn Out Filter ElementsReplace
RO Membrane MisplacedReinstall
Bent TubingStraighten
Feed Valve ClosedOpen
Tank Valve ClosedOpen
RO System LeakingLeaking ConnectionReconnect
Damaged ConnectionReplace
Loose Faucet ConnectionReconnect
Damaged Faucet StemReplace
Blocked Drain LineUnblock
Misplaced Drain SaddleRealign
Misplaced Filter Housing O-RingReposition
Worn Out Filter Housing O-ringReplace
Loose Membrane Housing CapTighten
Damaged Filter HousingReplace
RO Dispenser Flow IssuesLow Tank PressureRepressurize
Damaged Air BladderReplace
Storage Tank Pressure Too HighRelease Pressure
Low Feed Water PressureIncrease Pressure or Use Pump
Worn Out RO MembraneReplace
Worn Out Filter ElementsReplace
RO Membrane MisplacedReinstall
Blocked Flow RestrictorUnblock
Bent TubingStraighten
Feed Valve ClosedOpen
Tank Valve ClosedOpen
Filtered Water Tastes or Smells BadWorn Out Filter ElementsReplace
Fouled RO MembraneReplace
Stagnant WaterDrain + Flush System
RO System Making Noisy GurglesAir InsideWill Vanish with Time
Bent TubingStraighten
Clogged Drain ConnectionUnblock
Loose ConnectionTighten

RO System Drains Constantly

Let’s begin with the most common problem, i.e., a constantly running drain line.

You must know that as reverse osmosis systems filter water they produce wastewater[1] that runs down the drain pipe. But it is essential to understand how the unit works to identify malfunctioning.

An RO unit operates through water pressure. Water enters the system, passes the RO membrane, and is stored in a storage tank.

The ASO (automatic shut off) valve constantly measures water feed and pressure in said tank. When the storage tank pressure reaches ⅔ of the line pressure, the ASO valve shuts off, stopping water flow.

Similarly, the check valve – a one-way valve – prevents water from flowing down the drainpipe to maintain pressure in the tank.

Why Does the Drain Line Keep Running

Given these details, here are the most common causes that lead to a system draining continuously.

  1. RO units can’t function unless the feed water supply pressure is above 40 psi. Installing a water pressure pump can solve the issue.
  2. A clogged RO membrane might be causing problems. Replacing the filter can help.
  3. The drain line has a flow restrictor installed in it. You must check whether it’s in good shape or not. If your system constantly drains while making a lot of noise, a broken flow restrictor is a likely cause.  A replacement will solve the issue.
  4. Sometimes, improper installation can lead to a lot of problems. You can take apart the unit and fix it again carefully. Make sure to tighten all parts correctly and set them up according to instructions.
  5. Likewise, if the storage tank is not pressurized appropriately, the unit will constantly be drawing feed water. As a result, the RO system is unable to shut off, wasting tons of water.
  6. If either of the two valves malfunction, ASO or check valve, the storage tank will not reach desired water pressure.

Fixing RO Storage Tank Pressure

The storage tank is divided into two chambers, one for water and the other for air. Let’s begin by identifying if the air-filled chamber is depressurized.

First, empty your storage tank and then use a pressure gauge to measure the pressure. If the reading is between 6-8 psi, the storage tank is working flawlessly. Hence, you can skip this solution and move on to check the valves.

On the other hand, anything below 5 psi requires you to repressurize the tank. You will need a bicycle pump or an air compressor. Here is how to do it.

  1. Start by turning off the water supply.
  2. Then open the faucet to empty the remaining water in the storage tank.
  3. Jiggle it to see if there is still some water left. Then, carefully hook the bicycle pump to the Schrader valve on the tank’s side. Next, pump out any remaining water and then measure the pressure using a tire pressure gauge. If it’s lower than 6 psi, pump three or four times and measure again.
  4. The optimum working pressure can be under 8 psi. If you pumped in more pressure, quickly press the center of the Schrader valve to release some air.
  5. Finally, turn on the tank valve and the water supply.

Experts advise you to repressurize your RO tank every year when you change your filters.

If repressurizing your storage tank doesn’t solve the drainage issue, chances are the air chamber inside is punctured. Unfortunately, you will need to replace the entire tank to fix the problem.

Check Broken Valves

If the RO tank is working at optimum pressure, the valves might be broken. Here is how you can figure out if that’s the case.

  1. Before you begin, make sure the storage tank is completely full.
  2. Now, remove a couple of glasses of water to lower pressure in the tank. This will signify the unit to start operating again.
  3. At the same time, you must turn off the tank valve so it can’t draw more water in.
  4. After a couple of minutes, check whether the drain line is running or not. If it’s off, the valves are working to maintain the balance. If not, either the ASO or the check valve is defective.

Here is how you can figure out which valve is faulty.

  1. Allow the tank to fill completely.
  2. Turn off the incoming water supply but keep the tank valve open.
  3. Now, check the drain line to see whether the water is draining or not.
  4. If it is, the check valve is broken.
  5. If drainage has stopped, it signifies a broken ASO valve.
  6. You can replace the faulty valve to solve the issue.

Storage Tank Does Not Fill Up

Needless to say, the first solution is to ensure the storage tank valve is turned on. Another elementary problem, often overlooked, is a bent pipe that restricts water flow. Before moving on to below solutions, please ensure there are no sharp turns or twists in the tubing.

Here are a few other reasons that could stop your RO tank from filling up completely.

Faulty RO Membrane

If the RO membrane gets clogged or corrupted, very little water will flow to the storage tank. Thus, it may seem like it takes ages to fill up.

This usually happens where water is too hard, clogging the membrane sooner than you’d think. Therefore, people living in areas with very hard water should change their RO membranes more often.

Likewise, they can also install a water softener before the filtration system to filter out magnesium and calcium. Again, this will increase the life of the RO filter element.

On the other hand, an ill-fitted RO membrane will negatively affect performance. So make sure it is installed correctly.

Low Water Pressure

As mentioned earlier, an RO system requires at least 40 psi to work effectively. If the pressure of your water supply isn’t sufficient, you must use a booster/permeate pump to help RO work adequately.

High Storage Tank Pressure

A higher initial pressure (above 8 psi) in the storage tank will stop the water flow before the tank is full. Use a pressure gauge to monitor the pressure and release some if it is above the desired level.

Troubleshooting a Leaking RO System

Reverse Osmosis Troubleshooting - Problems and Solutions Thumbnail

A water-based appliance that never leaks? Yes, at some point, all of us face a leaking water filter. But, don’t worry, we got you sorted.

If you have identified what part of your unit is leaking, you are already one step ahead.

Leaking Fitting

The main reason for a leaking fitting is that the tubing has not been appropriately pushed in to create a proper seal. An easy fix is to mark ¾ inch at the end of the tubing and make sure the line disappears when you fit it in the fitting.

Moreover, a deep scratch on the tubing might prevent it from sealing completely. Replace the tubing if you see any wear and tear on it.

RO Faucet Leaking

A faucet that drips constantly could be an indicator of a loose fitting. Check all connections as described above.

On the other hand, if you see the bottom of the faucet is leaking, it means you need to replace it.

Air Gap Faucet Leaking

A leaking air gap in the RO faucet can introduce contaminants in your filtered water. Therefore it should be fixed promptly.

Choked Drain Line

The most common reason for ‘air gap’ leakage is a disruption in water flow, usually in the drain line. Mostly, when the drain line gets clogged with debris or chunks, the wastewater backwashes into the system and splashes out of the air gap.

To fix this issue, you must unclog the system’s drain line. You can use a brush or a wire cleaner and push out any debris.

To prevent your drain line from getting clogged in the future, avoid flushing big food particles or trash down the drain. Moreover, you can occasionally use drain cleaners to prevent choking.

Drain Saddle

With continuous usage, the drain saddle can move from its place. As a result, the water cannot flow freely into the drain. Check that the drain line and saddle are correctly aligned to prevent restricted flow.

Bent Tubing

Another reason is an improper installation of the tubing on this connection. Too much tubing tends to bend and obstructs water flow. Check that the tube is as straight as possible to ensure water does not backwash into the air gap.

RO Filter Housing Leaking

Here are the most common reasons for leakage in a filter housing:

  • A faulty O-ring.
  • O-ring not fixed appropriately to form a seal. Replace the O-ring to prevent further leaks.
  • A damaged housing. Replacement is necessary to fix the problem.
  • The membrane housing cap is not tightened correctly or has loosened over time. Check occasionally and tighten to prevent leakage.

Here is how you can replace O-rings:

  1. Begin by turning off the feed water supply and storage tank valve.
  2. Twist the filter housing to remove it.
  3. Carefully examine the O-rings to see if they’re scratched, broken or out of place.
  4. Replace with a new set if needed and screw the housing back on tightly using a wrench. Be careful not to overtighten.
  5. Turn on feed water.

RO Dispenser Flow Issues

trickling faucet

Slow, little or no water flow in the RO faucet can be caused by a few reasons.

Low Feed Water Pressure

The most common reason is low water pressure or low volume. Installing a pressure pump to boost water pressure will help you reach the optimum (more than 40 psi) desired by the RO system.

Damaged Storage Tank

Another reason can be a damaged storage tank. As mentioned earlier, if the air chamber in the storage tank has lost integrity, there won’t be enough pressure to push up water towards the faucet. As a result, the water flows in a trickle or is barely enough to meet your needs.

In order to fix this, first, check if the tank is full or not. If it’s full and still water flow to the faucet is restricted, you are likely dealing with a damaged tank.

Here’s how you can be sure if the tank needs replacement.

  1. Use a tire gauge to measure the pressure in the empty tank.
  2. Regulate it to 6-8 psi and observe the unit for a few days.
  3. If the problem persists, the air chamber is punctured, and the tank needs to be replaced.

Clogged or Misaligned Filter Element

If the feed water is too hard, your RO membrane can jam too soon. Hence, an earlier replacement may solve the issue. Similarly, installing a water softener before your filtration unit can prevent premature clogging.

On the other hand, if the RO membrane is not fitted correctly, the water flow could be restricted. Therefore, ensure that installation is perfect for solving the issue.

Damaged Flow Restrictor

A problematic flow restrictor in the drain line can also result in low water pressure and improper functioning of the system.

Twisted Tubing

Ensure all tubing run straight and have no sharp turn to allow for smooth, unrestricted water flow.

Closed Storage Tank Valve

The storage tank might have been closed by mistake. Make sure that the valve is open and filtered water can go through it.

Filtered Water Tastes or Smells Bad

While reverse osmosis is famous for delivering the best tasting water free from foul odors, a few reasons can lead to bad tasting water.

RO Membrane Failure

Due to a high TDS (total dissolved solids) breakout, the RO membrane can foul quickly.[2] Therefore, replacing the membrane is the only practical solution.

Clogged Filters

An RO system features more than one filter element, including the sediment filters, carbon filters, etc. Proper maintenance and regularly changing each stage are critical to optimum performance.

Stagnant Water in RO Tank

Were you on a vacation or a short weekend trip? If the water stays in the RO tank for too long, it can become prone to bacterial growth, leading to weird taste and smell.

So, whenever you use the system after a few days, it’s best to completely let the unused water flush out.

Compromised Tank or Housings

Moreover, the storage tank or filter housings may accumulate harmful pathogens that can result in foul-tasting waster. Occasionally sanitizing the tank and the housings is a simple and quick way to ensure that you have a squeaky clean unit free of unwanted microorganism growth.

You can use household bleach, an NSF-certified sanitizer or chlorine for disinfecting the entire unit.

RO System Making Noisy Gurgles

The RO system usually makes noise when a lot of water flows down the drain at a time. The sound is amplified when you install a new system or replace a cartridge.

Another contributor to loud sounds can be the position of the drain saddle. Place it on the crossover to reduce noise. Moreover, ensure tubing runs straight and has no sharp bends to cause interruption.

If nothing works and the sounds are too loud for you to bear, it’s best to check all connections.


In conclusion, reverse osmosis systems come with their own set of unique problems. Most are simple to fix.

An RO system which drains constantly usually has to do with an under-pressurized or damaged storage tank or a broken ASO or check valve.

If the storage tank does not fill up, check if the valve is fully open or if tubing is bent. Other potential causes are a faulty membrane, low water pressure, or overpressure in the storage tank.

Leaking is often caused by improper connections. You are trying to fix a leaking air gap faucet? Check the drain line and drain saddle. When filter housings are leaking, first, check the O-rings.

Low or no flow from the RO faucet can be an indicator for low feed pressure, a damaged storage tank or flow restrictor, and twisted tubing among other things.

When you sense bad taste or smell, check the filter elements and storage tank.

And lastly, gurgling noises can come from a misplaced drain saddle and bent tubing.

Further Reading


Meet Rory Mullan

Rory Mullan Rory has joined the Water Masterz team as a contributing writer. He has covered all sorts of topics in the last several years.

Outside of his writing work, Rory enjoys photographing the Irish landscape and making music!

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