RO Troubleshooting: problems and solutions


ro troubleshooting

After installing the Reverse Osmosis system you might encounter some problems. Issues can occur straight after the installation or some months later. This can happen after changing the filter or tinkering with the system. Here is a list of the most known problems and possible solutions. Consider this as a checklist. If the described solution for a particular problem is not the right one, then proceed to the following solution until you find the cause and fix it.

The most common issues can be summed up into the following categories. More detailed causes and explanations are following.

1• No water at all
• Little or slow water flow
2• Continuous drain – no shut-of
• Noisy gurgle while draining
3• Leaking faucet
• Leaking air gap faucet
• Leaking from a filter housing or fitting
4• Taste, odor, or looks of water is unpleasant
1RO tank is not filling up or the flow from the faucet is too slowSolution
 The storage tank pressure is too lowMeasure then repressurize
 Tank air bladder has a holeReplace the tank
 The storage tank pressure is too highMeasure then release pressure
 Feedwater pressure below 40 psiInstall a booster or permeate pump
 Reverse osmosis membrane is worn outReplace the membrane
 Clogged filterReplace the filter
 RO membrane is not properly installedDismantle and readjust
 Clogged flow restrictor  Unclog, clean, or replace.  
 Bent tubing  Straighten all the lines and arrange them orderly
 Feedwater valve is closedSimply open the valve
 Water storage tank valve closedOpen the tank valve
2RO system drains constantly and water keeps runningSolution
 The storage tank pressure is too lowMeasure and repressurise accordingly
 The tank air bladder is rupturedReplace the tank
 The shut-off valve is brokenTest and replace
 Check valve is brokenTest and replace
 The system is installed improperlyRe-check the whole system and resemble
 Reverse osmosis membrane is worn-outReplace the membrane
 The flow restrictor is brokenReplace
3Leaking faucetSolution
 Loose connectionTighten
 Damaged faucet stemReplace faucet
 Clogged drain line (air gap faucets only)  Unclog and clean the line
 Shifted drain saddle (air gap faucets only)Realign drain saddle with drain hole.
3Noisy drain line or air gap faucetSolution
 The system is new or filters were replaced recentlyNoise should be gone over time
 Tubing is bent Straighten all water lines
 A block in drain saddle or tubing Straighten and unblock
 Connection with outside air Check system and tighten loose connections
4Taste or odor of water is unpleasantSolution
 Old and dirty filters or membraneReplace and clean the system
 Old water in the systemFlush the entire system once or twice
4Water looks cloudySolution
 Some air is trapped in the newly installed system or filter.Will go away over time

Reverse Osmosis system is not working

If you’re wondering why won’t water come out of my reverse osmosis system, you’re in the right place. First of all, if your RO system is not producing water this can be a result of a few things. So we need to narrow down and identify the precise issue in order to fix it. As an example – if everything was fine, but your reverse osmosis system is not working after changing filters then you know where to start looking.

Reverse Osmosis system is not producing enough water

This can happen as a wake-up call when one day you realize that your reverse osmosis water flow is slow.

The right question in this situation to ask is – why does my reverse osmosis system have low pressure?

The main problem might be a result of a malfunctioning storage tank. The water tank of a standard RO system has two chambers inside. One is solely for water and another is for air. These chambers are separated by a rubber wall, called an air bladder. When purified water is pushed inside the tank, the blader moves down and the air pressure under it increases. After the tank is full, the water purification process stops. Then, the pressure inside the air chamber is pushing the water upwards and through the RO faucet.

In order to know for sure if the tank is working properly, you need to measure the pressure inside the tank. Don’t worry, it’s quite simple to do.

1) First empty the tank. Open the faucet on the sink and wait until water stops flowing. A full tank can weigh around 25 lbs. While an empty one will weigh nothing.

2) When the tank is empty, take a pressure gauge and measure the pressure inside. It’s the same type of valve that’s used for bicycles so a simple pressure gauge and a hand pump will work just fine. Look for a valve under the tank or on the side. Most of the time it will be covered with a cap. Generally, most tanks should be between 6 to 8 psi. Check the label for optimal value.

3) If the pressure is lower you can repressurize the tank with a bicycle pump. But do so carefully and don’t exceed the optimal values as too high pressure will result in the tank not filling up with water to its limits or not filling up at all.

If the tank is still heavy after step 1), and has some water inside but no water is coming through the tap then you need to increase the pressure inside the air chamber to push the water out. Then adjust the pressure accordingly.

If the same problem occurs after a day or two this means that the bladder is ruptured and you need to get a new tank.

Also once the tank is empty of water try to move it a little. If you hear water sloshing inside it most likely means that the bladder has a hole in it and some water is inside the air chamber. This is a clear sign that a new tank is needed.

Other possible causes and solutions

Low pressure in the water supply line

Slow water flow from the faucet can reflect the overall low feed pressure where water enters the system. Generally, pressure below 40 psi requires a booster or permeate pump for the RO system to work effectively.

Old and clogged filters or nonfunctional RO membrane

Filters that have been in use for a while will accumulate dirt and sediment. Based on the original manufacturer recommendations, filters have to be changed every six to twelve months.

Clogging of the membrane can happen when it has to deal with exceptionally hard water. To prevent this you can replace membranes more often but the cost will add up over time. Another option is to install a pre-treatment unit like a water softener.

Reverse Osmosis system tank is not filling

When a storage tank is empty or partially empty and does not fill this indicates something about pressure.

Most likely, the feed pressure is too low. The water should enter an RO system at a pressure of at least 40 psi. Below that you need to increase the pressure in the entire home or install a specific permeate pump designed for RO systems.

Quite rare, but if the pressure inside the tank is too high, then the system can’t fill up with water. In order to measure the pressure follow the guidelines in the previous chapter. If there’s a need, reduce it to be around 6 to 8 psi.

Bent tubing or closed water feed valve

These are last on the list but should be checked as the first possible solutions. Maybe someone was tinkering with the system or cleaning around and forgot to open one of the valves.

Bent tubing should be straightened as well.

Reverse Osmosis system constantly drains water

It’s possible to hear a sound when the Reverse Osmosis system drain line keeps running water down the pipes. The overly noisy sound is addressed later, but all in all, RO should not drain water nonstop when it’s not used.

Usually, RO system shuts down once the tank pressure reaches 2/3 of the supply line pressure. This is regulated by an automatic shut-off (ASO) valve.

To test if the ASO valve is working correctly follow these steps:

1) Allow the tank to be filled completely.

2) Let two or three glasses of water through the RO faucet. This will start the system to produce more water.

3) Close the tank valve to simulate a full tank and wait for four to five minutes.

4) Check if the water stops flowing down the drain by listening or pulling the drain line from the saddle.

If the water stopped, this means that both valves are working as they should.

If water continues to run down the drain this can mean one of two things. Either ASO or the check valve is broken. Continue with a second test.

1) Refill the tank.

2) Keep the tank valve open but shut off the feed water valve.

3) Check if the water is running down the drain.

If no water is flowing this indicates that the ASO valve is broken.

If water is flowing it means it’s flowing from the tank, to the drain. The check valve is broken.

You can order and replace the check and ASO valves from the manufacturer of your system.

Other possible causes for constant drain

The RO membrane is in bad condition

An old RO membrane can be damaged and in need of replacement.

Something is out of place

The same issue can occur if you just installed the system or replaced RO membrane with a new one. There might be an air gap. Inspect if the tubing is cut in straight lines and has no noticeable worn marks. In this case, carefully reconnect RO membrane and the tubing leading to the tank.

A worn-out flow restrictor

Inside the drain line is a flow restrictor. It provides resistance needed for RO membrane to work. And meters water flow rate going down the drain. It’s made to work precisely with the output of the membrane that the system has. So if a flow restrictor is worn-out, it needs to be replaced with the same model and type one.

Reverse Osmosis water system is leaking

If you notice a puddle of water, first of all, turn off the feed valve.

Can you identify where in particular the leak is coming from? Just by touching and looking for wetness, you should be able to guess. If you find the spot, or even if you don’t proceed further.

Put something under the system. If a bowl fits, or a towel to soak up the water.

Turn on the feed water valve and open the RO faucet. You need to make sure that the water is coming from the spot that you suspect. Most of the time it’s easy to find where the leak is happening. Now you just need to fix it.

Leaking Filter or RO membrane housing

Such leaks are caused by a number of problems.

  • Not enough tightened filter of membrane housings – tighten by hand and use the housing wrench to tighten an additional quarter turn or so. Don’t overdo it.
  • A misplaced or worn-out rubber o-ring – if housings are tight enough then inspect o-rings. Housing leaks are almost always caused by an o-ring defect. Reused o-rings will be slightly stretched that’s why it’s a good idea to use some silicone o-ring lubricant. Alternatively, an extra set of o-rings can save you a lot of time.
  •  A cracked housing. These are usually made of plastic and in case of physical damage need to be replaced.
  • Tubing is not set firmly. A loose tubing can’t create a proper seal. It should be inserted nearly 1″ into the fitting and quick connector. Make sure that you cut the tubing in a straight line. A cut at an angle won’t form a proper seal.

Leaky Faucet

A dripping faucet can happen after some time of use. To stop the leaking try tightening all connections. Then push the tubing further into the port. If the leaking continues the faucet should be replaced.

Leaking Air Gap Faucet

This might happen if your system has an Air Gap Faucet rather than a simple faucet. The issue of some water coming through the air gap faucet hole is called an “air gap leak”.

In order to fix it, you simply need to clean the drain line leading from the faucet to the drain saddle. A narrow wire brush or special pipe cleaner will work. Look for clogs at a drain saddle and do clean the saddle itself.

Also, it’s possible that the saddle shifted a little so the holes are not aligned properly. This will most likely restrict the water flow down the drain. Measure the hole alignment and retighten everything back in place.

Noisy Gurgle

Why does Reverse Osmosis system make a noisy drain sound that is unusual?

  • If you recently replaced one of the filters and turned the system back on this might cause the sounds to arise. Nothing to worry about, because the sounds are created by air that is being pushed out of the system. The matter should resolve itself after a day or two. If it doesn’t then it’s probably worth investigating.
  • Make sure that all the tubing is straight and nothing has awkward angles. The noise can be coming from the restrictor and the drain tube or saddle. Inspect and clean these parts as was described in the previous section.
  • Other causes can be because the system has a small gap and extra air enters through it. This can be solved by rechecking and retightening all the housings and tube connection points.
  • Finally, a drain saddle that is not installed correctly can result in sounds coming up the sink. Try reinstalling the drain saddle on a horizontal pipe instead of vertical, leading down the sink.

Reverse Osmosis water has a bad taste

Reverse Osmosis purified water has a slightly different taste than regular water. However, if your RO water suddenly starts to taste differently, this can be caused by a number of things. Some of them are happening beyond the system and should be addressed.

Otherwise, bad taste or odor can originate from the system itself. Old, worn out or almost clogged filters and membranes can start to accumulate biological material that becomes a place for bacteria growth. This happens after months or years of use. That’s why manufacturers recommend changing filters and RO membranes on a schedule. And some systems come with indicators installed. In addition to filter change, it’s recommended to clean and sanitize your RO system periodically.

Unused system and stale water

Some amount of bacteria can grow in still water that sits inside the RO storage tank. The tank can be sanitized as well, but after leaving the system for a while you should flush some water through it. Empty the tank once or twice and check if the issue is still there. If so, then proceed to washing the system and installing new filters afterward.

Final words on RO troubleshooting

An RO system takes some maintenance. With care and attention, you can maintain yours for many years to come. And with these simple solutions, you can fix most of the issues that can happen.

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