Gravity Water Filter vs Reverse Osmosis System: Which to Choose?
Written by: Alexandra Uta // Last Updated: Mar 25, 2023
This page may contain affiliate links. If you buy a product or service through such a link we earn a commission at no extra cost to you. Learn more.
When it comes to ensuring clean and safe drinking water, two popular options on the market are gravity water filters and reverse osmosis systems.
Both claim to remove lots of contaminants from water, but which one is better? And which should you choose?
In this article, we’ll compare gravity water filters to reverse osmosis systems, and help you determine which one serves you best. At the end of this article, you’ll understand how the two systems work, and you’ll be able to choose the right one for you.
Contents
show
Key Takeaways
Gravity water purifier vs RO – the system to choose depends on your use case and water quality.
- A gravity water filter is best if you need water for indoor + outdoor activities with no functioning plumbing system, like camping. It’s also great for homes with fewer contaminants in their water.
- A reverse osmosis system is super powerful and works best for home water containing a wide range of contaminants.
Gravity Water Filters vs. Reverse Osmosis System — Which Should You Choose?
So, gravity water filters vs reverse osmosis systems – which choose you choose?
Well, your decision mainly depends on why you need a water filter. The thing is, each type of water treatment system has its pros and cons.
For example, gravity water filters do not require electricity or a plumbing system to work, so they are great for emergencies and outdoor water filtration. But they require manual refilling and produce water rather slowly (often takes over two hours to fill up the bottom tank), so they may not be practical for very large households.
Reverse osmosis systems remove a wide range of contaminants — great if you have different types of pollutants in your water. But they often waste a lot of water and they require more work when it comes to maintenance.
In essence, your individual circumstance, preferences, and use case will help you determine your best option.
Let’s dig a little deeper!
Have Your Water Quality Tested + Consider Your Use Case
Before choosing any water filter, the first thing to do is test your water quality. You want to know the exact contaminants in your water and then check if a reverse osmosis or gravity water filter can remove those contaminants.
By the way, NSF certifications or testing can help you know which contaminants a certain filter can remove (there is NSF standard 42, for example, for chlorine removal and standard 53 for harmful contaminants in general, such as lead).
Speaking of the “use case”, your intended use for the water also determines which water filter you need. If you need water for outdoor activities like camping, your only choice is a gravity water filter. But if it’s only for home use, it’s up to your home water quality to determine if RO is the better option.
How to test water quality? Either check your latest Consumer Confidence Report or do your own testing!
What Are Reverse Osmosis Systems and How Do They Work?
Reverse osmosis systems use high pressure to force water through a semipermeable membrane that blocks contaminants. They come in different types; countertop, under sink, and whole house systems. Most homes use an under sink RO system because they are cost-effective, efficient, and easy to install. So in this guide, we’re focusing on under sink RO units.
Under sink RO systems are usually installed under the kitchen sink, where they filter water and store it in a tank before releasing it to the dedicated faucet. They typically have 3 to 5 filter stages, including the primary RO membrane, a sediment filter, and 1 or 2 carbon filters.
What Are Gravity-Based Water Filters and How Do They Work?
Gravity-based water filters use gravitational force to push water through one or more filter elements. They have two chambers separated by the filtration stage.
The upper chamber is where you add your raw water. Gravity directs the water in the upper section to flow through the filters (which remove contaminants) and into the lower chamber.
Two types of gravity water filters include countertop gravity filters and gravity filter bags. But for this guide, we’ll stick with countertop gravity units.
Detailed Comparison
Now, we’ll compare a typical under sink RO water system to a countertop gravity filter using cost, installation, maintenance, and other factors. As you read, pick out which factors matter the most to you and which filter wins under those factors. That way, you can make the best buying decision!
Purchase Price
Under sink reverse osmosis systems cost between $150 and $600, depending on the brand, quality, and number of filtration stages. Gravity water filters, on the other hand, cost between $250 to $350. Their exact price mainly depends on the unit size, filtration process, and few other factors.
Installation
You have to install a reverse osmosis system after purchase. You may call a professional, but hookup is really no big deal. If you have basic plumbing tools (wrench, screwdriver, tubing cutter), you can DIY within one or two hours.
You’ll do some drilling if you install an under sink RO system for the first time. But you don’t need drilling for countertop units; they are autarchic or connect it to your existing kitchen faucet.
Gravity filters are autarchic, too, which means no plumbing installation. Just prime the filters, arrange the system, fill it with water, and it’s ready. When it comes to installation ease, gravity water filters win.
Contaminants Being Removed
Reverse osmosis is a highly effective water purification process. All reverse osmosis systems use a primary RO membrane plus sediment and carbon filters (and sometimes others), so they all remove the same types of contaminants and sometimes even more: Heavy metals, salts, chemicals like pesticides, VOCs, some microbes, sediments, TDS, etc. – the full spectrum.
Gravity filtration is also effective because the water flows slowly through the filter media, so it gets enough time to trap contaminants. However, gravity water filters can use a variety of filter elements, so the types and number of contaminants removed vary from model to model.
The most effective types of gravity water filters use a ceramic filter element as the outer shell and a core of carbon or mixed filter media. These can remove viruses, pathogenic bacteria, cysts, chlorine and chloramine, pesticides, disinfection byproducts, heavy metals, drug residues, and sediments among other things.
Bottom line, if you use the right gravity-fed water purifier, it can compete with many reverse osmosis systems.
Pathogenic Bacteria
These are dangerous bacteria in the water that can cause diseases. Ceramic gravity filters are excellent at removing pathogenic bacteria. Although RO membranes do also work, they are not designed for it.
Water Taste
RO water doesn’t taste bad, but some people find the taste a tad too flat due to the lack of minerals. Powerful gravity filters can give water a much better taste.
Flow Rate
Water flow rates depend on the specific filter system in question and how you use it.
- Some reverse osmosis water filter system can provide one water gallon per 10-15 minutes, while some can be as slow as half a gallon (or even less) per hour.
- The flow rate in gravity water filters mainly depends on the number of filter elements you use in parallel. But at the very least, you’ll get one water gallon per hour. You can get over 10 gallons of water per hour using a really large system.
Dependence on Water Pressure
Reverse osmosis depends on water pressure from your plumbing system. So if there’s a power outage, an RO system might not work.
Gravity water filters are better in this regard. They do not need external water pressure or electricity since they rely on gravity force to work.
Filter Life
The lifespan of a RO membrane is two to five years. But you must replace the pre and post-filters every 6 to 12 months.
A gravity filter’s lifespan depends on how much water you use. A filter element will often produce 1,000 to 3,000 water gallons before needing replacement, so service life depends on how fast you use that quantity. Usually, it takes up to a few years.
Cleaning and Maintenance (Cost)
If you use a gravity water filter, you must often commit a considerable amount of time to clean and maintain it. The tanks require up to weekly cleaning to prevent biofilm, a layer of microbes. You also have to scrub and reprime the filter elements every week or so, especially if your water contains lots of sediment or is hard. But apart from that, maintenance is pretty cheap. You’ll spend less than $100 per year to replace filters.
Reverse osmosis systems are way easier to clean and maintain. The system needs only annual cleaning (although this once-a-year cleaning takes a bit more time). Then, you’ll replace the filters when you clean the system too, which means once or two times a year. Filter replacement also takes time, but not too much. As for the cost, you’ll spend about $100 and up to $200 per year to replace filters.
Further Reading:
Pros and Cons of Gravity Water Purifiers vs. RO Systems
Now, let’s highlight the advantages and disadvantages of gravity water purifiers vs reverse osmosis.
Reverse Osmosis
Here are the benefits and downsides of a reverse osmosis water filter.
Pro: Broad Contaminant Removal
RO water purification removes up to 99.9% of chemicals, sediments, metals, and almost all other water contaminants.
Pro: Safe Drinking Water
By removing all pollutants, reverse osmosis makes your water safe to drink.
Pro: Better Taste and Smell
RO filtration improves your water taste. It also enhances its smell by eliminating odor-causing chemicals.
Pro: Chemical-Free
Reverse osmosis systems do not use chemicals to purify water. You don’t have to worry about chemical residues in your water.
Pro: Installation and Maintenance Ease
As mentioned, RO systems are relatively easy to install and maintain. You can install one yourself, and maintenance involves only annual cleaning and replacing filter elements on schedule.
Pro: Customizable
You can add extras (like a remineralizer) to an RO system to customize it and better meet your filtration needs.
Pro: No More Bottled Water
RO filters defeat the need for bottled water in a home since they make your home water healthy – saves you a lot of money.
Con: Wastes Water
A standard of-the-shelf reverse osmosis system wastes about four to five water gallons per gallon of filtered water.
If you use a booster pump, you can reduce the amount of wastewater by up to 90% and more.
Con: Very Slow
RO systems filter water very slowly. But this con will hardly affect you if you use a tank RO system.
Con: Removes Essential Minerals
In a bid to remove lots of contaminants, reverse osmosis also removes essential minerals from water.
Tip: A remineralizer adds useful minerals to your water after filtration.
Con: Space
RO filters take up space, whether under sink or whole house systems.
Con: Extra Faucet Needed
You need an extra faucet on your sink to use an under-sink model. That means you may need to drill your sink if there’s no extra tap space.
Gravity Filtration
Here are the pros and cons of gravity water filters.
Pro: Clean Drinking Water
Sophisticated gravity filters remove most if not all potentially dangerous contaminants, so your water becomes safe for drinking.
Pro: Improve Water Taste and Smell
An effective gravity water filter removes chlorine, manganese, and hydrogen sulfide — stuff that alters your water taste and smell. With the bad guys gone, your water tastes and smells much better.
Pro: Great for Emergencies
Unlike RO, gravity water filters can work without electricity and a plumbing system. As long as there’s a water source, even if it’s a lake, gravity-based will work and provide you with clean water!
Pro: Environmentally Friendly
Producing no wastewater at all, gravity water filters are more environmentally friendly.
Pro: Save Money
If you add filter purchase, installation, and maintenance costs and compare them to buying water bottles, you’ll find that gravity filters are quite affordable. In fact, they are an investment to save money.
Pro: Simple Installation and Maintenance
Gravity water filters do not need any plumbing installation; simply assemble the system in a few minutes, and you’re good to go. While cleaning may be regular, it usually takes only a few minutes.
Con: Manual Refilling
You must manually add water to the upper tank, which may be inconvenient for some.
Con: Slow Output
Gravity-based water filters produce water slowly because there’s low pressure in the system, way lower than the pressure in your plumbing.
When to Use and When to Skip a Reverse Osmosis System
In our opinion, you should use a reverse osmosis system if your water contains a wide range of contaminants and contaminant types that you cannot remove with a specific filter (like a carbon filter).
You can skip RO if there are only a few contaminants that specific filters can remove in your home water.
When to Use and When to Skip a Gravity Water Filter
It’s best to use a gravity water system when filtering your home and outdoor water. Gravity water filters are not attached to a plumbing system (so you can easily switch between indoor and outdoor use). They are also very effective, especially if you use a suitable model.
Skip a gravity water filter if you’re filtering home water that contains many different types of contaminants.
If you have any questions about reverse osmosis vs gravity filter please don’t hesitate to leave a comment below!
About the Author Alexandra Uta
Information provided on BOS is for educational purposes only. The products and services we review may not be right for your individual circumstances.
We adhere to strict editorial guidelines. Rest assured, the opinions expressed have not been provided, reviewed, or otherwise endorsed by our partners – they are unbiased, independent, and the author’s alone. Our licensed experts fact-check all content for accuracy. It is accurate as of the date posted and to the best of our knowledge.