RO (Reverse Osmosis) Water Purifiers – Pros and Cons

Last Updated on 13 February, 2024 by Sourav Roy

RO water purifiers are devices that purify water through the process of reverse osmosis. These types of water purifiers use a partially permeable membrane to remove contaminants from the water.

RO (Reverse Osmosis) Water Purifiers

Dirt molecules, unwanted ions, and sediments are restricted due to the presence of the membrane. When purifying water in this way, solid particles, no matter how small in size, are retained on the pressurized side of the membrane. Whereas, the filtered liquid is permitted to pass onto the user side.

Considering the amount of pollution that we humans generate daily, food and water have to be treated before consumption. That is where RO water purifiers come in the picture. They remove all harmful substances from the water and always provide you with pure drinking water.

RO purifiers come under the category of the most reliable water purifiers. There is a term known as TDS levels. Total Dissolved Solids level is a rating for indicating the concentration of dissolved particles in the water. A best RO water purifier eliminates TDS contents from water and provides you with the purest drinking water.

The three types of water purifiers are:

We shall read about the mechanism, types, pros, and cons of RO water purifiers.

Recommended Reading: RO vs UV vs UF – Water Purifiers


How does Reverse Osmosis work?

How does Reverse Osmosis work

Remember, we studied about osmosis in chemistry and biology class?

The classic definition of osmosis would be the natural reaction of liquids to move from a lower concentration area to an area of a higher concentration when separated by a semi-permeable membrane. Take the relationship between soil and water, for example. The water seeps into the soil, and thus osmosis takes place.

Reverse osmosis is the bang opposite of osmosis. In this case, the liquid is transferred from a region of higher to lower concentration. That beats the natural movement of fluids.

But how does it happen? The answer is force.

Say you have a path for liquid flow that is divided by a semi-permeable membrane. One side of your path consists of water with salts and minerals. Whereas, the other side has cleaner water or no water at all. When force is applied from the higher concentration side, purified water seeps through. That happens because of the semi-permeable membrane and the direction that pressure was applied from.

Precisely the same functionality is used in RO water purifiers.

That is why the best RO water purifiers consistently give out clean and drinkable water. All solids, whether undissolved or dissolved, are restricted entry to the other side because of the top-notch membrane engineering.


What is an RO Water Purifier?

What is an RO Water Purifier

Unlike other filters that function and go about purification using high-frequency light or additional compounds, the RO purifier thrives on a membrane. The membrane contains pores that are not more than 0.0006 microns in size. These pores are super useful to restrict impurities.

It doesn’t matter whether it is mud, salts, dust, or even grass. In fact, molecules of lead, arsenic, and cadmium are also kept at bay.

Do you live in a region where water contamination is high? Have your TDS tests indicated above-average levels of danger? An RO water purifier can bring much-needed security to you and your family in such cases.

If you consume these impurities, the side effects won’t be instant. Instead, these contaminants will spread in your body over time. Eventually, you will be diagnosed with severe illnesses such as cancer or irreparable organ damage.

Regular water purifiers also cleanse your water, but only to a limit. If your water source exhibits a TDS rating in the number of thousands, your standard water purifier will prove ineffective.

You need to look for an RO water purifier that clears the clutter and replenishes the mineral content. The best RO water purifier with features of a TDS controller and a mineralizer is what you need.

Recommended Reading: How to check TDS of water


How does an RO Water Purifier Function?

How does an RO Water Purifier Function

If you are aware of necessary water filtration procedures, you would also know how the restricted impurities are left on one side. You have to clean the filter before allowing water to pass again manually. If you don’t clear it, the sediments clog the membrane, and a small amount of water gets a chance to pass.

That is where RO water purifiers are handy. They consist of a cross filtration system. Two outlets are allocated to each RO water purifier. One end is for water to flow out on your side. But the other outlet eliminates the impurities that are rejected by the semi-permeable membrane.

Once you switch your purifier off, there will be a suction action on the backflow outlet. That sucks away all the contaminants that were restricted by the funnel. Guess what? The system is so effective that the rejected water can be detected with over 90% impurities.

Don’t be one of those who want to refilter this water and exploit the system. If the quantity of contaminants is high, then your system can get strained and stop functioning.

The wise choice is to use this water to wipe the floor or clean the toilet.

The RO filter will stop any particle that possesses a molecular weight of over 200. Whether it’s a mineral, ion, or any other sediment, it does not matter. Water’s molecular weight is only 18. You can imagine the level of precaution that the RO filters add.

You must take additional measures to prevent sodium ions from passing through. As their weight consist of a single digit, you will need specialized filters to keep them out. Think about it, if you had a groundwater system installed in your home, then RO purifiers could be a saviour.

Due to their impeccable water cleansing ability, water poured through an RO filter will measure below seven on the pH scale. Consider this mildly acidic and 100% fit for human consumption.

Recommended Reading: 9 Best Water Purifiers In India 2024


Parts of an RO Water Purifier

Four parts of an RO water purifier that you must know about are mentioned below:

1. Inlet Valve

RO Water Purifier Inlet Valve

This directly fits onto your side, as the water source. There is a visible tube that goes all the way to the sediment filter (which you cannot see).

2. Sediment Filter

RO Water Purifier Sediment Filter

Impurities that can travel further and clog the RO system are restricted here. Keep in mind, if solid particles are evident in your water, then the sediment filter has stopped working.

3. Pre-Activated Carbon Filter

RO Water Purifier Pre-Activated Carbon Filter

Chlorine can be found in every municipal water source. The issue persists in the RO membrane’s sensitivity to chlorine. Exposure to chlorine can deem the RO filter ineffective. Pre-activated carbon filters work in unison to erase all traces of chlorine.

Additional carbon filters are present after the RO membrane. They have been placed to disintegrate any undesirable smell that may have formed during filtration.

4. RO Membrane

RO Water Purifier RO Membrane

This is the final filter/membrane that gets rid of any existing impurities that made it through the sediment and pre-activated carbon filters. Because of microorganisms and bacteria that yet manage to find their way across, supplementary filtration systems need to be attached ahead.

5. Ultraviolet and Ultra-Filtration Filters

RO Water Purifier Ultraviolet and Ultra-Filtration Filters

The intimidating action of UV and UF filters kills any existing bacteria or microorganisms, thus purifying your water to its maximum extent.

By now, you are well aware of how thoroughly the RO purifiers operate to clear almost all minerals from the water. There would be an undoubted sacrifice of healthy minerals. The water is fueled with mineralizers towards its final stages to stabilize this loss of essential minerals.

The on/off switch is used to initiate or stop the flow of water in the tank. The pressure is directed inwards the membrane when the device is on.

On the other hand, when the switch is off, the force is directed outwards. That clears contaminated water and impurities through the other outlet.

Recommended Reading: UV (Ultra-Violet) Water Purifiers – Pros and Cons


What are the Types of Reverse Osmosis Water Purifiers?

India offers two generic RO water purifiers as per the health requirements and regulations of the country:

1. Undersink RO Water Purifier

Undersink RO Water Purifier

As the name suggests, this water purifier is installed under the sink. The close proximity to the kitchen sink makes it easy to use and faster to react.

These filter types are even equipped with a water storage container that is pressurized by air. Whether its maximum capacity of 5 litres is achieved or not, the built-up pressure helps to transfer water to the outlet.

These purifiers do not occupy too much space. The best part is the area of installation. Even better, the fact that it is under the sink saves up valuable space in the open.

All the contaminated water can be redirected to another tank or pipe as per your needs. You can connect it to the washing machine, backyard hose, or even to your society’s wastewater inlet.

Most importantly, due to the tank being situated under the sink, the direction of pressure favours the water’s force. That is not the case with wall mounted RO water purifiers.


2. Wall Mounted RO Water Purifier

Wall Mounted RO Water Purifier

These systems are not hidden and are very much visible to the user, although it consists of one complete compact unit that can be mounted on the wall.

Another advantage is its ability to store up to 10 litres of water, for which additional equipment is required.

The best part is that both these water purifiers will let you access the stored water despite a power cut.

Advantages of an RO Water Purifier

  • UV water purifiers help kill bacteria and other microorganisms, but they fail to eradicate their dead bodies. RO water purifiers, on the other hand, will kill and eliminate all contaminants.
  • Heavy metals such as lead, cadmium, iron, and arsenic are filtered out of the water. That is possible only due to the 0.0005 to 0.0007-micron size of the semi-permeable membrane.
  • A TDS (Total Dissolved Salts) controller or a mineralizer can be added to enrich the water with minerals. Other water filters have no such replenishing arrangements.
  • Compact in case of storage.
  • Even the frequency of maintenance checks is reduced as the air pressure system automates cleaning the funnel.
  • 100% safe and purified water is available for drinking 24/7.

Disadvantages of an RO Water Purifier

  • High pressure is a mandatory requirement due to the automated extraction of contaminated water. Sadly, this rejected water is generally wasted.
  • Electricity is also a compulsion. The consistent purification of incoming water cannot work without electricity. All you can access is already cleaned and stored water.
  • 50% of the total water used in the process is rejected due to contaminants. That is not a resource-friendly option.

The facts state that the benefits of an RO water purifier far outweigh the downsides. If you are looking for a healthy source of drinking water, then some sacrifices have to be made. This much knowledge about RO water purifiers must be enough to help you look for the ideal attributes. Go ahead, make your choice, and do let us know if this guide influenced your decision.

Recommended Reading: 9 Best Water Purifiers In India 2024


RO Water Purifier: Frequently Asked Questions

How much is the electricity consumption rate for RO water purifiers?

Not much. It is considered almost negligible in your electricity bill. Keeping the system on for 40 hours will consume 1 unit. Each 1 unit pours at least 400 to 500 litres of purified water.

Is the maintenance cost of RO water purifiers too high?

Not at all! You would need to get a water purifier maintenance check every 3 to 4 months. Due to the air pressurized purifying system, it generally clears the sediments that were filtered out. If you get a RO water purifier from a trusted brand, then you would rarely have to clean the filter yourself. For these reasons, the maintenance cost is low.

How much should I pay for a good quality RO water purifier?

You will get water purifiers ranging from 7000 to 50000 INR. Consider 12000 to 25000 INR as an optimal rate to get a top-notch water filter. With proper care, it can last for as long as ten years.

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