We reviewed 20 new and bestselling reverse osmosis water filter systems to find the best RO systems for your home, ideal for a range of budgets and needs. Let this be your one-stop RO system review and shopping guide - we’ve done the legwork of comparing a range of products, and have narrowed it down to our top overall pick, a budget pick, and eight additional high-quality options. Most of these under sink home reverse osmosis systems support DIY installation, too, so you don’t have to pay for a pro if you have some handy skills if your own.
GPD - The production capacity of a reverse osmosis water filter system is measured in Gallons Per Day. But how does that help you figure out the best reverse osmosis filter system for you? Thankfully, you don’t have to measure your household water use personally - it’s easier to go by the estimate of the United States Geological Survey: the average person in the US uses 80-100 gallons a day. Ignoring use that happens outside the home, it’s safe to assume each member of your household uses at least 50 gallons per day. Not all of this is coming out of your sink, of course, but the best reverse osmosis water system for your home should have a higher GPD depending on your water usage. If you have a small household with low water usage overall, a 50 GPD RO under sink filter system should be enough. For heavier usage, you may want to look for home reverse osmosis system closer to 100 GPD if you want to use the filtered water for cooking or cleaning as well as drinking.
99% Contaminant Removal - One of the privileges of living in a developed country is not having to worry about contaminated water. But news stories about water crises can definitely make you wonder, and most people who use wells to provide water to their homes will notice minerals like iron and sulfur that affect the taste, smell, and appearance of their water. Even if you’re on a city water supply, chloramine and other chemicals used to sanitize the water don’t taste so great. One of the best things about an RO water system for your home is that this type of filtering removes water pollutants as small as .0001 microns for, you guessed it, 99% contaminant removal. For context, .0001 microns is smaller than most individual bacteria and viruses. So an undersink reverse osmosis system is certain to provide you with water of great quality, but that looks, tastes, and smells much better than city water.
WQA Certified - The Water Quality Association seal is one of the marks of quality to look for in reverse osmosis water filter reviews. This association is a not-for-profit international trade association that represents all levels of the water treatment industry. Companies have to send in an application requesting that their products go through the WQA’s testing process to see if it meets their guidelines for performance, efficiency, and safety. The WQA even audits the facilities where the product is produced before bestowing the Gold Seal mark on the product. This seal lasts five years, and then the product has to be re-tested and certified all over again. Getting certifications from independent organizations like the WQA is a great way for a company to show dedication to consumer protection and a willingness to open up their production process for scrutiny.
Includes Faucet - Although you can hook up an RO water system for your home to an existing faucet, installing a second faucet just for the RO system can help you limit the use of the RO system to things like washing vegetables or filling a cup of water to drink. This way you can use your regular water system for things like filling up a mop bucket or a pot of water for pasta, where taste and absolute purity don’t really matter. Including this faucet is a “bonus feature” that not all RO water systems incorporate, so if you know you want to only use the RO system for certain tasks, it’s really convenient not to have to buy the second faucet separately. Most RO systems make DIY installation easy with video tutorials and customer support numbers, so you’ll have access to experts if you need help installing your home RO system.
Warranty - A warranty is there as a promise from the manufacturer that if on the off chance you get a defective product, they won’t leave you hanging. They ensure that the company will repair or replace your RO system if, despite treating it well, it doesn’t perform the way it should. We like loooonnng warranties because they show some serious commitment from the company to the quality of their products. However, a longer warranty also tends to come with a higher price tag--but if you can afford it, we highly recommend investing in a product with a longer warranty. They can offer some peace of mind in a world where things seem to be made with consistently decreasing lifespans. Also, several of these RO systems come with “satisfaction guarantees,” which are basically extended return policies if you change your mind about the system.
Size - The main limit on an under sink RO filter system is the space available, well, under your sink. A system with a larger GPD tank capacity or one with multiple filter stages comes with lots of benefits, but none of that matters if the system doesn’t fit! Make sure to measure the area under your sink and compare it to the dimensions of the reverse osmosis water system you’re considering. Most of the systems here are about the same size, with a standard three-gallon tank. If you have plenty of room, you can even switch out the tank included by the manufacturer for a larger one if you want. Be wary of things like garbage disposal systems that can eat up available space. It’s always worth double checking your space before buying.
Now that you know what to look for in a reverse osmosis water filter system, let's dive right into the reverse osmosis system buying guide below to figure out the best RO filter system for you. The main differences you’ll see between these systems are the GPD and the certifications received from independent industry groups. Rest assured, all winning products on this list offer top quality and value.