RO Membrane Filters: The Ultimate FAQ Guide

Choosing RO membrane filters can be an overwhelming task.

A reason this guide will make everything easy for you by exploring all information you need about reverse osmosis membrane filters.

Let’s dive right in.

What Is A RO Membrane Filter?

A RO membrane filter is simply a filter membrane with a reverse osmosis configuration.

Its primary function is to remove contaminants or debris from the water.

The filter is a semipermeable layer through which you push water under pressure to deionize it or demineralize it.

 reverse Osmosis Membrane Filters

Reverse Osmosis Membrane Filters

What Are The Components Of RO Membrane Filter?

The components are:-

  • An optional pressure regulator. This allows you to inspect and control the feed water pressure in your reverse osmosis system.
  • Sediment pre-filter. This component removes insoluble oxides and debris that may plug the drain flow restrictor or clog the membrane surface.
  • Carbon filter for chloramine and chlorine removal. Chlorine and chloramines degrade the RO membranes very easily. This filter protects the membrane from quick deterioration.
  • Shut off the valve. You can use this valve to cut off the water supply or to eliminate drain flow.
  • Reverse osmosis membrane. This is the most important part of the system. Its main purpose is to remove dissolved solids like metals or salts from the feed water.
  • Post filter to remove any remaining odors or tastes from the water.
  • Pressurized water storage tank.
  • Water supply.

How Does A RO Membrane Filters Work?

 Ilustration Of A RO membrane At Work

Illustration Of A RO Membrane Filter At Work

The RO membrane is specifically the most vital element in any reverse osmosis system.

The membrane typically comprises two semipermeable material sheets that are 2” –  8” inches in diameter.

They are spiral wound and designed to keep back contaminants while letting clean water flow through.

Forty inches is the standard length for RO membranes that are intended for use in industrial applications.

These membranes are put into housings, usually six at a time. These housings are then arranged for many parallel flow stages or streams.

This means that reverse osmosis can occur in many stages.

Osmosis is reversed using force and pressure from a pumping system.

The pumping forces feed water through the semipermeable RO membranes.

This will forcefully reverse the natural process of osmosis and leave all contaminants behind. Meanwhile, the clean water will flow through the system.

Once this process is complete, you can use the highly purified water for other purposes.

You can recycle, drain or flush the filtered impurities.

What RO Membrane Filter Works Best For Each Application?

CTA membrane filters are more susceptible to fouling than TFC/TFM but are more tolerant to chlorine.

They reject up to 93 percent of common impurities; use this type if your budget requirements cannot cater to auxiliary equipment like carbon filters.

TFM or TFC reject 98 percent of impurities and are not easily affected by organic fouling.

The downside to this type is that you can only use it to purify water without chlorine content. If you wish to do so, you must use a carbon pretreatment filter.

In What Way Is The RO Membrane Filter Similar To Regular Distillers?

 Water Purified Via Distillation

Water Purified Via Distillation

Both regular distillers and RO membrane filters reduce contaminant levels in the water. However, they do so in two completely different processes.

Regular distillers work by the principle of condensation, while RO membrane filters work by the principle of filtration.

The similarity between both systems arises from the chemical removal stage. Both are heavily reliant on carbon filtration processes.

Why Is Water Pressure An Important Consideration When Using RO Membrane Filters?

Water Pressure is perhaps the most important considerations when it comes to working with RO membrane filters.

The water pressure is essentially responsible for flushing the rejected debris and impurities away after forcing water through the membranes.

Low water pressure could result in premature fouling and low production by the RO membrane filter.

The recommended water pressure for working with an RO membrane filter is 60 PSI.

If you notice pressure drops below 40 PSI, you should consider boosting it using a pump as it is insufficient.

What Is The Functional Lifespan Of An RO Membrane Filter?

With the regular replacement of worn-out parts and servicing/maintenance, your RO membrane should last at least five years.

Other factors such as the nature of water being processed also come into play in determining the expected lifespan of the RO membrane filter.

Is It Possible To Hook The RO Membrane Filter On Other Appliances?

Yes, it is possible.

You can hook the RO membrane filter onto other appliances like refrigerators or Icemakers.

Since pressure varies with different appliances, you might want to check with the manufactures first.

The RO membrane filter can only achieve 2/3 of total line pressure.

A Water Purifier Fitted With A RO Membrane Filter

A Water Purifier Fitted With A RO Membrane Filter

Do RO Membrane Filters Remove Important Minerals?

Yes, the RO membrane filters remove nearly 97% of the total mineral content in the water.

However, this should not be cause for any alarm.

The resulting water is usually within an acceptable range for the body since it is still palatable.

When it comes to drinking water, the mineral concern is usually very controversial.

How Does Water Softener Affect RO Membrane Filters?

Yes, water softeners affect the RO membrane filters. They can help extend the lifespan of the membrane.

They will not cause any harm to the RO membrane filter.

Limescale chemicals like magnesium and calcium are usually the hardest chemicals to filter out.

Sodium(which is used in water softeners) is very easy to filter out. 99% of it gets filtered out. The point is, water softeners will not harm your RO membrane filter.

Do RO Membrane Filters Require Electricity To Work?

RO membrane filters do not require electricity to work.

They only require electricity if you decide to incorporate an ultraviolet lamp or an electricity-powered pressure boost pump.

RO membrane filters only require water pressure to work.

How Do You Maintain And Clean A RO Membrane Filter?

You should perform maintenance procedures to ensure your RO membrane filter works to ensure high water quality. Such procedures include:-

Changing The RO Filters And Reverse Osmosis Membrane.

Try your best to replace the reverse osmosis membrane, the post-filters, and the pre-filters periodically.

Replace the post-filters at least once a year and the pre-filters once every 6 to 12 months.

For the membrane, replace after 2-4 years if your feed water is hard and after 5-7 years if your feed water is soft.

Ensure that the carbon filter is in good condition because chlorine will degrade your system. You can change it every year.

If your feed has high chlorine content, you should consider replacing the pre-filters more frequently, i.e., six months rather than 12.

Also, use a TDS meter to check whether or not your RO membrane filter is in perfect working condition.

Draining The Reverse Osmosis Storage Tank.

You should do this once every fortnight. Draining enables the RO membrane filter to turn the stored water completely.

Do this to maintain the quality of your RO membrane filter.

Sanitizing The Reverse Osmosis Storage Tank

Ensure that your storage tank is sanitized every time you replace the RO membrane. Slime grows on the tanks over time.

Use a sanitizing solution to clean the tank. You can do this by running the solution through the system annually. This will remove the slime.

A Cleaned RO Filter

A Cleaned RO Filter

What Is The Cost Of Maintaining RO Membrane Filter?

To ensure peak performance of the RO membrane filters, you need to replace only the post-filters and the pre-filters.

You can do this on an annual basis. Ultimately, the frequency of use and water quality will affect how often you need to replace filters.

On average, replacing these filters at least once every year should cost around $ 0.30 each day.

The RO membrane will last up to five years.

What Is The Difference Between Distilled Water And RO Membrane Filtered Water?

Distilled water typically has fewer ppm of common mineral content like sodium compared to RO membrane filtered water.

However, when it comes to low boiling point volatile chemicals like chloramines, distillers are less efficient than RO membrane filters.

These chloramines are usually used as disinfectants instead of chlorine and are not sufficiently removed by distillers.

Paired with carbon filters, reverse osmosis filters remove chloramines leaving you with very pure water.

How Do You Troubleshoot A RO Membrane Filter System?

The following are common reverse osmosis membrane filter system problems and their solutions.

Slower Than Usual Water Flow

This problem arises from low pressure. You will notice low feed water volume.

To solve this:-

Simply check to ensure optimal water pressure, i.e., 60 PSI in the RO tank. If it is not, use a pressure gauge to raise the pressure carefully.

If the bladder in the RO tank cannot hold the pressure, you should replace the whole tank.

The System Running Without Stopping

This problem occurs if the check valve is broken or the shut-off valve does not close as required.

It may also arise as a result of improper membrane installation.

To solve this:-

Measure the pressure to ensure that the pressure is between 40-60 PSI.

Replace the check valve if it is broken.

Odor And Bad Taste

This is usually caused by stagnant water, worn-out membranes, and depleted post and pre-filters.

To solve this:-

Replace the depleted parts.

Change the storage water periodically to reduce air and bubbles. The foul odor will disappear, and your water will taste good.

Faucet Leakage

This occurs if the parts of your RO membrane filter are loosely fitted.

Locate the origin of the leakage.

To solve this:-

Simply drain the ports and saddle, fix the tubing, and tighten the fittings.

Noisy Drain Or Faucet

This is a very common problem users experience with RO membrane filters. It arises from air getting pushed out as you change filter cartridges or newly installing a system.

The noise gradually reduces in under one week.

What Contaminants Do RO Membrane Filters Remove?

The RO membrane removes dissolved contaminants and impurities like fluoride and arsenic through the membrane.

They have a broad range of reductions due to their inclusion of sediment and carbon filtration.

The carbon filter removes odors, bad taste, and chlorine, while the sediment filter rids debris and dirt.

The RO membrane filter removes the following chemicals:-

  • Pesticides and herbicides.
  • VOCs
  • Arsenic
  • Chlorine
  • Sediments
  • Salt
  • Fluoride

You should note that the RO membrane filters do not remove viruses and bacteria.

It may initially remove bacterial contaminants, but the contaminants may grow on the RO membrane.

This may contaminate your water supply and potentially put your health at risk.

We recommend UV Disinfection if you want to remove viruses and living organisms from your feed water.

What Are The Stages Involved In Reverse Osmosis Filtering?

Reverse osmosis filtering occurs in three stages. These stages are:

Sediment Filtration

This is the first stage in the process. Here, all suspended solids or debris, i.e., sediments that are larger than one micron, are removed.

This process is easy because, during the filtration process, these sediments will accumulate on the RO membrane surface.

Chlorine Removal

This is the second stage in the process. One downside of RO membrane filters is that they can be degraded by chlorine.

Therefore, chlorine has to be removed. This is done by metering reduction agents like sodium bisulfite or sodium thiosulfate upstream of the system.

An alternative way of chlorine removal is by using activated carbon filtration methods.

RO Membranes

This is the final stage in the process.

The membranes are 0.0001 microns in pore size.

This tiny pore size will exclude dissolved impurities and contaminants and allow water molecules to flow through.

How Do You Clean The RO Membrane Filter?

Cleaning the RO membrane filter is simple. Impurities, debris, or scale may clog up the membrane.

You can dislodge them using chemicals to have a clean and efficient RO membrane filter.

What Is The Difference Between Disinfection And Cleaning With Regard To RO Membrane Filters?

The surface of the RO membrane filter can be fouled by materials such as biological and organic matter, calcium precipitates, and metal oxide hydrates.

To get rid of this fouling, you clean the membrane.

On the other hand, disinfection is done to the storage tank.

The process is also known as sanitization.

Ensure that your storage tank is sanitized every time you replace the RO membrane.

Slime grows on the tanks over time. Use a sanitizing solution to clean the tank. You can do this by running the solution through the system annually.

This will remove the slime.

What Materials Are RO Membrane Filters Made From?

The RO membrane filter is primarily a thin composite film membrane that consists of three layers.

These layers are:-

  • An ultra-thin polyamide layer- this acts as a barrier layer on the membrane’s top surface.
  • A microporous interlayer made from polysulfone.
  • A support web made from polyester.

 Materials That Make Up The RO Membrane Filters

Materials That Make Up The RO Membrane Filter

These materials are best suited because they are customizable to sizes appropriate to efficient reverse osmosis processes, i.e., <200 nm for the polyamide layer.

They can also achieve pore sizes as tiny as 0.0001 microns.

What Is Scaling And Fouling In Regard To RO Membrane Filters?

Membrane Scaling

When water is forced through the membrane, the dissolved contaminants flow into the drain. Some of these contaminants come out of the solution over time to create a thick scale.

Scale accumulates rapidly if there is insufficient water inflow into the drain and an excess flow through the membrane.

Membrane Fouling

This is quite similar to membrane scaling.

The only difference is that living organisms shut down the membrane by slimming like scale. In this case, the accumulation is of living organisms, not inorganic minerals.

How Do You Flush A RO Membrane Filter?

Flushing means getting the air out of your RO membrane filter from manufacturing.

Flushing will saturate the membranes because they are usually dried after manufacturing.

To flush it, simply put the membrane under running water or submerge it for a few minutes.

Which Factors Affect The Quality Of Water Produced By The RO Membrane Filter?

The following factors will affect the quality of water produced by the RO membrane filter:-


Different RO membranes are built for different chemical deterioration resistance, production rates, and impurity rejections.

We can supply an appropriate membrane to your process requirements to ensure filtration requirements are met.

Total Dissolved Contaminants/Solids

The typical TDS of feed water should be lower than 500 parts per million, i.e., ppm.

The amount and quality of water produced will be significantly low if the TDS exceeds this limit.

You can improve the water quality by using a booster pump to increase pressure on the RO membrane.


The ideal water temperature for reverse osmosis is 76 °F or 25 °C.

Also, the production will be low if the feed water is at a temperature of 40 °F or four °C or below.

The high temperature will damage the membranes and, in turn, lower the quality of the produced water.

Thus, we recommend purifying water with maximum temperatures of 35 °C or 95 °F.

Water Pressure

Water quality and quantity increase with pressure.

The ideal water temperature is 60 PSI. If your pressure is below this, you might consider using a booster pump.

Using our RO membrane filter comes with an assurance of maintained pressure at 60 PSI throughout.

What Is The Price Of An RO Membrane Filter?

The cost ranges between $16.99 to $500 depending on the type you require. The price is worth it because of the benefits they present.

A typical RO membrane filter removes 95% of all dissolved contaminants and presents the following benefits:-

  • It is easy to install, use, clean, and maintain.
  • It reduces odor and bad taste.
  • Most importantly, it reduced harmful dissolved contaminant levels in your water.
  • It is a more environmentally friendly option than other options like bottled water.

How Do You Store The RO Membrane Filters?

  • Store the RO membrane filters out of direct sunlight in cool areas. The temperature of the storage area should range between -5.5 °C to 45 °C.
  • Leave all-new elements or parts in their original packaging.
  • Preserve the membranes in solutions with 20% AM-225 Glycerine and 2% AM-88 preservatives.
  • Examine the preservatives frequently. If it doesn’t appear clear, remove the membrane and represerve. Ensure that the preservative pH does not drop below 3.

What Types Of RO Membrane Filters Are There?

There are two common types: Cellulose Triacetate membrane filters and Thin Film Composite Filters, i.e., TFM or TCM.

The difference between these two arises from their chlorine tolerance and filtration ability.

CTA membrane filters are more susceptible to fouling than TFC/TFM but are more tolerant to chlorine.

They reject up to 93 percent of common impurities.

TFM or TFC reject 98 percent of impurities and are not easily affected by organic fouling.

The downside to this type is that you can only use it to purify water without chlorine content. If you wish to do so, you must use a carbon pretreatment filter.

 Thin Film Membrane In RO Membrane Filter

Thin Film Membrane In RO Membrane Filter

Additional Resoures:

Reverse Osmosis Technology

RO Purifier Machine

RO Unit

RO Machine For Home

If you need any RO membrne filter, contact us now.

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