Tankless Vs Tank Reverse Osmosis System: Which Is Better?

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Tankless Vs Tank Reverse Osmosis System_Is tankless better than tank reverse osmosis

Investing in a reverse osmosis system is a must, especially if you drink tap water where a lot of impurities, contaminants, and other substances could pose a threat to your health and quality of life. But once you start shopping, you’ll notice that there are two options: a tank and tankless reverse osmosis (RO) system. In this guide, we’ll walk you through the difference between a tankless vs tank reverse osmosis system, their pros and cons, and how you can choose the right one for your household.

Quick Comparison Of Tankless Vs Tank Reverse Osmosis Systems

Tankless Reverse OsmosisTank Reverse Osmosis
Requires ElectricityYesNo
Efficient With Waste WaterYesNo
Takes Less SpaceYesNo
Fast Filter ChangeYesNo
Emergency Water StorageNoYes
Water Pump NoiseYesNo

What Is A Tankless Reverse Osmosis System?

A tankless reverse osmosis (RO) system functions quite similarly to its traditional tank-based counterpart in terms of the actual filtration process. The primary difference is that tankless units are smaller and don’t come with a storage tank. 

Because there is no storage tank, an integrated electric booster pump is used to create the optimal water pressure.  This is what allows a tankless RO to supply endless on demand filtered water.     

These tankless varieties are also designed with more advanced technology, which means that they are easier to operate, more efficient in terms of purifying the water, and of course, more practical if you have a small kitchen space to work with. 

Benefits Of A Tankless Reverse Osmosis System

  1. Take less under-sink space: Space saving is perhaps the biggest benefit of a tankless RO system because you can free up that space where your tank used to be and use it for extra storage in your kitchen. Tankless reverse osmosis systems can save you up to 75% more space than bulky traditional systems.
  2. Easy to maintain: With a tankless RO system, you don’t need to worry about changing filters as often for most tankless units because these advanced systems are more effective than tank RO units. And when it’s time to replace the filters, it takes only a few seconds. Tankless variants are also easier to maintain since you don’t need to think about the tank being contaminated.
  3. Wastewater efficient: Tankless RO systems are designed to work efficiently in purifying your water without producing a lot of wastewater in the process. This will help you reduce your water bills significantly and put your savings towards other expenses. The average reverse osmosis system uses a 4:1 waste water ratio, meaning 4 gallons of waste water to one gallon of purified water. With efficient tankless units, this ratio can be as high as 1:2 now, so only one gallon of waste water for 2 gallons of purified water.
  4. Doesn’t have contamination risk: Unlike a tank where you’re storing water and possibly exposing it to contamination, a tankless RO system takes water straight from the source, purifies it, and delivers it right to a dedicated faucet. Tank-based systems run the risk of growing bacteria in the water holding tank over time. Not only that, but many tank based RO’s utilize plastic filter housings to protect the filters, which are also a source of bacteria risk.

Drawbacks Of A Tankless Reverse Osmosis System

  1. Can be more expensive: Purchasing any RO system is an investment in your health and upgrading to a tankless RO system can cost more than a tank based option. But all the benefits that you get from making this investment will surely be worthwhile in the long-term when you factor in filter replacement costs, water efficiency, and filtration performance. This is not to say that all tankless reverse osmosis systems cost more than storage tank RO systems. There are some residential tank based units that are more expensive than tankless, and vice versa.
  2. Require electricity: Perhaps the biggest disadvantage of tankless RO systems, is that they require electricity to operate. This is not that big of a deal in reality, just make sure that you have an electrical outlet nearby when installing it or that you can get access to electricity.
  3. No water in power outage: Since tankless RO systems will only work with electric power, you’ll either need to buy a generator or find a backup water source in case there’s an outage. This is why a tankless RO system is not the most ideal option in emergencies. And because there is no storage tank, you wont have access to those precious few gallons stored up like a tank based model.
  4. Less customizable: Unlike tank RO systems, tankless variants offer fewer customization options, especially with accessories, filters, or attachments because of their enclosed design and form factor. Common additions to tankless reverse osmosis systems would be a UV sanitization light, a remineralization filter, and a few others.

What Is A Storage Tank Reverse Osmosis System?

You’ll see a tank RO system in most homes since it’s been the traditional purifying system for many years now. Here, you have a water purifying system with different types of filters depending on your needs and the addition of a pressure tank where all of that filtered drinking water is stored and ready for use. 

Although tank RO systems have proven their efficiency over time, they take a longer time to filter out and regenerate water, which is why you can expect a slower output than a tankless RO system.

Benefits Of A Tank Reverse Osmosis System

  1. Stores water in power outage: If you experience water outages often, then a tank RO system is the best option since it has a tank that stores water to ensure that you have a continuous water supply even when your main source is cut off temporarily or in the case of an emergency.
  2. Operate quietly: Most of these tank RO systems don’t require electricity to work except for those models with a UV filter: This makes them a lot quieter than tankless RO systems with water pumps that can be noisy at times.
  3. More budget-friendly: Since tank RO systems have been around longer, you’ll have more options with different price points to fit your budget. Tankless RO systems can be more expensive at the high end mainly because of the better efficiency and the technology that comes with them.
  4. More customizable: Tank RO systems are more versatile than tankless ones since you can customize them to fit your exact needs. For instance, if you want that extra filter power, you can add a add modular filter choices to the units. Or if you want higher water pressure, you can add a water booster pump.

Drawbacks Of A Tank Reverse Osmosis System

  1. Take more under sink space: Since this type of RO system includes a tank, you’ll need a bigger floor or under-sink space to accommodate it. So, if you don’t have that space, you might consider going for a tankless option instead.
  2. Produce more wastewater: The mechanism in which a tank RO system operates can produce a lot of wastewater, which can result in higher utility bills each month.
  3. Higher contamination risk: While having water stored in a tank can be convenient, especially during emergencies, leaving the water in that tank for too long could put your water at risk for contamination and secondary pollution. So, if you notice that your water tastes odd, you should replace it right away.
  4. Takes time to refill tank: If your tank is full, you can enjoy good water output from your tank RO system. But if it’s near empty, you’ll need to wait for a while for it to regenerate before you can enjoy steady water flow from your faucet.  

Key Factors When Deciding Between Tank Vs Tankless Reverse Osmosis

If you still can’t choose between a tank and tankless RO system, here are some key decision-making factors that you need to consider:

RO System Cost

Tank RO systems come in many variations since they have been around for a long time, so you can choose a solution depending on your budget. Undersink tank ROs usually range from about $200 up $1,000. A tankless RO system, on the other hand, has a slightly more expensive starting because of the technology and features included in it. They typically range from about $350 to $1,100. There are of course exceptions to those prices.

Source Water Contaminants

Like any filtration solution, you can’t know which option is best if you don’t know what contaminants you need to filter! That’s why we usually recommend starting with a good test of your home’s water to see what specifically needs to be targeted.

It also depends on if you have well water or municipal tap water. Or if you have a water softener. Your water can have a variety of things in it like fluoride, lead, iron, PFAs, and the list goes on. And while reverse osmosis, fortunately, removes almost all common contaminants, it helps to hone in on the very best RO filtration system for your issues.

In some cases, it may be necessary to have pre-filtration if your water is very harsh. If you have water packed with sediment or harsh chemicals, it can wear down the RO membranes and reduce its useful life.

Waste Water Efficiency (Waste Water Ratio)

When researching reverse osmosis systems, make sure to see what the waste water ratio for the specific unit is. Tankless RO systems help to cut down your utility bills since they are generally more efficient in reducing wastewater as compared to tank RO systems. That is not a blanket statement though, there are highly efficient tank based options out there. Just be sure to check the efficiency ratio on any product before you buy.

Water Pressure

If you already have bad water pressure in your home, a tank RO system could take longer to fill out the tank since it works mechanically. A tankless RO system, on the other hand, can provide you with consistent output because it uses a motor pump.  In some cases, the systems can have a built in booster pump to help with water pressure. If your home’s water pressure is below 35 psi, an option with a booster pump would be best.

UV Sterilization Light

UV sterilization is among the most effective ways to destroy viruses and bacteria in your water. If you know you have bacteria, or just want to play it safe, an RO system with UV light is a good idea. There are some models that come with a UV included, or you may be able to include it as an add-on. If the model you like does not have either of those options, you can always get a separate UV system to supplement your RO.


Reverse osmosis water filtration is so effective that it even removes the healthy minerals! If you like the mineral water taste, you will want an RO with remineralization capability. Similar to the UV light, you can get systems that include the remineralization filter or have it available as an add-on. These will add back healthy minerals like calcium, magnesium, potassium, and more.

A note on RO remineralization filters. Whether it’s a tankless vs tank reverse osmosis system, make sure if you get a mineral filter that it uses natural minerals that are premium quality. If you try to get a cheap version, the “mineral” filters are often low quality and filled with chemicals, causing more harm than good.

Undersink Space

Consider the amount of room you have to install an undersink RO system. If you have a large area with no constraints, then you are free and clear. If you have very little space, a tankless RO may be more suited for your needs.


Quality reverse osmosis systems that have industry certifications for the system or for the filters used are preferable. When you are doing your research, see if the product comes with any certifications.

The highest standard certification to look for is from the National Sanitation Foundation (NSF). If you see a system or its filters are NSF certified, you can have more peace of mind knowing it is high quality. There are different protocols to which filters can be certified by NSF, which you can read here.

Reverse Osmosis Tankless Vs Tank Filter Replacement Cost

Whether you’re using a tankless vs tank reverse osmosis system, you can expect to pay between approximately $100 for the RO membrane filter. They should last between 12 and 24 months depending on your water conditions and how well your system is maintained.

Each RO system, whether tankless or tank, has pre and post-filters too. Most of the time these are sediment filters, activated carbon filters, and finishing filters. These filters will last approximately 6 months to a year. But they are less expensive than the RO membrane filter. They might cost between $20 to $50 dollars depending on the filter type.

It’s essential to know how much reverse osmosis tankless vs tank reverse osmosis system filter replacement cost, so you know what your long-term costs for each product will be.

Final Thoughts on Tank Vs Tankless RO Systems

This tankless vs tank reverse osmosis system comparison should serve as your guide to making the right decision for your purchase. Regardless of which direction you go, all RO systems are an investment in your health, and a step in the right direction to reduce plastic bottle waste. If you take good care of your system, it should last you up to ten years. Thank you for reading!

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