The continued increase in water contamination in the US is alarming. More than ever, many homeowners & businesses have shifted to the use of water filters solution, especially the reverse osmosis(RO) water purification system. However, there are many different types of RO, that choosing the right one for you may be a bit confusing. This article will discuss one of the most popular RO options – the under the sink water filter or under counter RO filters.

Here is all you need to know before getting an under sink reverse osmosis(RO) water filter:

  • What is Under Sink Reverse Osmosis and how does it work?
  • Types of Under Sink Water Filters
  • Why should you consider installing an under sink RO water filtration system?
  • Are under sink water filters worth it?
  • Is Under Sink RO Filtered Water Good For You?
  • Why Drinking Filtered Water is Important
  • How to Choose the Best Under-Sink RO Water Filter – Buying Guide
  • Frequently Asked Questions (FAQs)

What is under sink RO and how does it work?

Just as the name suggests, the under sink RO system is designed to stay underneath your sink. The filter is integrated with the plumbing below your kitchen sink. It is then connected to an RO filter that uses a semi-permeable membrane to purify the water that comes out of your faucet.

An under the sink RO filter is one of the best ways to eliminate contaminants from drinking water. It works with more efficiency than regular water filters and also improves the smell and taste of your drinking water.

With the aid of a hydrostatic storage tank, an under counter water purifier ensures you have enough water flow whenever you need it. As a result, the under-counter RO provides a higher water output than wall-mounted and over the counter RO. To create a clearer picture, a typical under sink water filtration system takes about 15 seconds to fill up a one-liter bottle. The under sink reverse osmosis system is also sometimes referred to as the under counter reverse osmosis system.

Types of under sink water filters

There are two major types of under the sink water purifiers – the inline and the regular water filters.

Inline under the sink water filters

This type of under sink filter is connected directly to your water source using push fittings while you get purified water through your kitchen tap now.

Regular under the sink water filters

For the regular under the sink water filter installation, the mains line is split and connected to a separate filter tap. This way, you will have two fixtures at your kitchen sink – the ordinary kitchen faucet and the filtered water faucet.

You can also have the under sink water filter with a dispenser. This way, the system is connected to provide a three-way kitchen tap where you can get hot, cold, and filtered water.

Why should you consider installing an under sink RO water filtration system?

No doubt, all RO systems help you save money over time compared to buying bottled water. However, the under-sink RO system has a lot of advantages over other types of RO.

  • Ease of use – Under counter water purifiers are generally more convenient to use than over the counter filters or wall-mounted filters. The under-counter RO filter can be connected directly to your kitchen faucet, water dispenser, or refrigerator.
  • Large filtering capacity – They also have a large filtering capacity than most countertop RO systems.
  • Saves space – Under sink ROs are portable, and they save you a lot of space. They are best if you have a small kitchen or need to save space. Since they stay below the sink, they take little to no space in your kitchen work area.
  • Unlimited water supply – even when there is no electricity, the under-sink RO continues to provide water through the pressure from the storage tank.
  • Cheap to maintain – compared to the wall-mounted RO, the parts of the under-sink RO are much less expensive and easier to replace. 

Also Read: Reverse osmosis(RO) water filter system The truth & buying tips

Are under the sink water filters worth it?

When considering other options such as bottled water or taking your tap water directly, it is okay to wonder if under sink ROs are worth it. Let’s look at some of the advantages of under sink RO over different water sources.

Under sink RO vs Tap water

It’s no news that tap water in the US is prone to contamination. While the water may be pure from the source, contamination is possible as it passes through old pipes to your faucet. Water samples collected from over 40 states in the US show that the water contains harmful chemicals like lead, arsenic, chromium -6, and even nitrate from fertilizers.

Under sink RO features a semi-permeable RO membrane and series of filters that remove 99% of these impurities, giving you only pure, healthy water. And since tap water cannot be trusted, it is advisable to control what you drink by filtering your water using a reverse osmosis under sink system.

Under sink RO Vs Bottled water

The benefits of under sink RO over bottled water are numerous. We will discuss some of them below.

Filtering water from under sink filtration system is cost-effective compared to bottled water. You pay less for water from an under sink RO system than you will for bottled water in the long run. Even more, your bottled water mostly comes from tap water, and you cannot be too sure of its quality. With an under counter water filter system, you can filter your water and be rest assured of high quality at an unlimited supply.

Again, using under sink water filter is beneficial for the environment. Plastic waste from bottled water takes hundreds of years to degrade, making it much less eco-friendly than the under-counter RO. when you filter your water, you reduce the number of plastic wastes, which is good for mother earth.

Also, using an under counter reverse osmosis system allows you to have access to healthy and pure drinking water without the stress of lifting heavy plastic bottles of water from your dispenser. This is more common for businesses where employees have to change 50kg bottles often. Even more, you eliminate your risk of consuming water from bottles that have been sitting in the sun for an extended period. When bottled water has been in the sun, some harmful chemicals are produced by plastic, which may seep into the water.

In the end, an under sink water filter is definitely worth a try. The filter produces water that tastes and smells better, you can make your own water in unlimited quantity, and you’re sure of safe drinking water.

Also Read: Threats bottled water poses to ones health

Is under the sink RO filtered water good for you?

As tap water passes through pipes, it tends to gather up harmful contaminants, which eventually delivers to your faucet. Some of these include lead, arsenic, and many other chemicals that can result in adverse health effects. But with an under counter water filter, you’re able to purify the water that comes from your tap.

Under counter RO water is good for you. Drinking RO purified water reduces your exposure to water-related illnesses. The under sink reverse osmosis filter system removes dissolved contaminants, bacteria, chemicals, and heavy metals that could jeopardize your health.

Below is the list of harmful contaminants where under sink RO filter will be helpful to purify your water

Contaminants removed by under sink RO filter
Lead Manganese Phosphate
Zinc Arsenic Cyanide
Chlorine Giardia Lamblia Cysts Bacteria
Copper Fluoride Sediments
Nitrates Silver Barium
Protozoa Algae Sulfate
Selenium Radioactivity Viruses
Volatile Organics Mold Radium

Finally, under counter RO improves the taste, smell, and color of water through the sediment filters and post-carbon filter that polishes the water before it gets to your faucet.

Why drinking filtered water is important

Pure, healthy drinking water

One of the most apparent benefits of drinking filtered water is the effect on health. Unfiltered water has many impurities that can make one sick, so it is essential to purify water before drinking. The removal of pollutants from water reduces your exposure to water-related illnesses. Filtered water from an under-sink RO is free from contaminants such as lead, arsenic, aluminum, bacteria, dissolved salts, heavy metals, and other impurities that cannot be seen with the naked eyes.


Drinking filtered water from an under-sink RO has more benefits. One of these is remineralization. A 6- stage under-sink RO system adds back essential minerals that may have been lost during the filter process. These include calcium and magnesium, and other minerals that are beneficial to your health.

Promotes skin hydration and nutrient absorption

Filtered water also improves hydration and nutrient absorption. If your reverse osmosis under sink system includes an alkaline filter stage, you will have the additional benefit of drinking alkaline water. Alkaline water increases the rate at which your cells absorb the nutrient, promotes skin hydration, and your body’s metabolism.


Detoxification is another reason why filtered water is important. It is even more beneficial if you consume a lot of junk food and snacks. Filtered water helps the body eliminate toxins aster through the process of detoxification.

How to choose the best under the sink water filter – Buying guide

There are many factors to consider when choosing an under counter water filter system. These include the water flow rate, storage capacity, ease of use, plumbing and installation requirements, and filtration stages, and of course, and the cost.

Under the sink water filter output

The level of water output of an under counter water purifier is influenced by the rate at which the storage tank is refilled. For example, if the storage tank of your under-sink RO is refilled at, say, 50 gallons per day, then this means you have an output of one gallon every 30 minutes. High output under-counter RO systems are best for homes or businesses with large water needs. You can also go for a tankless RO system. A tankless reverse osmosis under sink system can produce up to 400 gallons of purified water on demand.

Tank size / Storage capacity

Under sink reverse osmosis systems have different water output and storage capacity. The rate at which water is produced at the faucet is not the same as when the storage tank is filled. While you can get water at the tap whenever you want, you must consider how much water your storage tank can take and how often it will have to be refilled based on your water use. A typical 5-gallon tank will store about 3 gallons of water with space for air pressure. So if you require a lot of water, then you should consider an under sink RO with a large tank size.

Installation Requirements

Some under sink ROs come with an instruction manual, but the process may be difficult if you are not plumbing inclined. Also, under sink installation usually requires some drilling and faucet fixing, so it is best left to professionals. We provide free installation for every under sink RO system, so you wouldn’t have to bother about installing your system yourself.

Filtration Quality

An under counter water purifier usually has a number of pre and post-filters, which are different from the reverse osmosis membrane filter itself. The number of filter stages of an RO system affects the filtration quality. To get the best out of your RO filter, consider one with at least 5-stage filtration.

Under the sink water filter cost

Cost is an important factor you consider when choosing an under-sink RO system. There are two options for which you can make a choice – buying or renting.

If you’re purchasing an under sink water filter for an apartment or business, you will need to factor in the price, the installation cost as well as the cost of maintenance. The price of an under sink RO can range between $200 to $1,000, while installation may cost up to $100 or more. A less expensive option is to rent an under sink RO.

Aquatech water systems offer high performance under sink water filtration systems on a monthly subscription rental basis. Renting an under sink RO is generally more pocket friendly than buying. Our rental options come with free maintenance and servicing. This will save you the cost of under sink water filter maintenance.

Frequently Asked Questions (FAQs)

Q – Do I need a professional to install an under the sink RO system?

Installing an under sink RO involves some drilling and may require the service of a professional. At Aquatech, all our under-sink RO systems come with free installation.

Q – Does my RO water filter system need servicing?

Yes, About once or twice a year, you may need to change your RO filters. Regular replacement of your filters will help your entire RO system lasts longer. A well maintained under sink RO should last up to five years. We provide free maintenance for our under sink RO systems.

Q – How long does under the sink RO system last?

Typically, an RO system lasts between 1 to 5 years. However, this depends mostly on the quality of water it filters and how often you change the pre-filter membranes. A well maintained RO system should last up to 5 years.

Q –  Are under the sink RO systems noisy?

No. When installed properly, an under counter water filter system will make soft sounds that are hardly noticeable. If your under sink RO is making distracting noises, then you should notify your plumber or installation technician.

Q – Why do people love under the sink RO systems?

There are numerous reasons why people prefer under-sink RO systems. Under sink Ro systems are durable and easy to maintain. They are also very compact and saves space. More importantly, they are very efficient in purifying water or drinking.


Whether you are a homeowner, tenant, or businessperson, it is vital that you (as well as your family and your employees) have access to clean and healthy drinking water. In a world where water-related illnesses are fast rising, you can take control of your health by using reverse osmosis water filters efficient in water purification.

For the best under sink reverse osmosis water filter, it is advisable to get one with a five-stage filtration and an extra 6th stage for alkalinization and remineralization. If you’re buying an under sink RO, you need to consider the purchase price, as well as the cost of installation, maintenance, and filter replacements.

However, you can easily rent an under-sink RO with Aquatech to benefit from our free installation, servicing, and maintenance.

Learn more about renting an under sink water filter or getting a free quote.

This article was originally published in Dec-2020 and was last updated in Jan-2023

Author: Sarah Williams

Category: RO Water Filters