What to Consider When Purchasing an RO System

Washing hands with RO filtered water

Reverse Osmosis Buyer's Guide

Before purchasing a reverse osmosis water filtration system, you may have questions that you want answered. Here, we address decisions such as air gap versus non-air gap RO faucets, how to connect a reverse osmosis system to a refrigerator, and what size system is the right fit for your home or application.

What to Know Before Buying a Reverse Osmosis Filtration System

So, you've decided to get serious about researching Reverse Osmosis Systems. Perfect. Before making a purchase, here are seven things to consider.

Number one

Do I need to buy a faucet?
RO systems require a specific faucet for the treated water to dispense. Most RO systems come with an RO spicket, but you can upgrade the faucet to match the color, finish and style of your existing sink fixtures. You might also consider what type of faucet is included with the RO system you purchase. For example the, the Axeon Solo RO system comes with a standard RO faucet, whereas the Microline TFC-400 comes with a designer chrome faucet.

Number two

Do you want an air gap or non-air gap faucet?
Non-air gap faucets do not have an “air gap” in the drain line to prevent drain water from being siphoned back into the system. However, non-air gap faucets are simpler to install, less noisy, and a check valve installed in the drain line can safely prevent backflow from the drain, which is why non-air gap is the most common type of faucet.

Number three

How many filtration stages should an RO system have?
RO systems typically come in 3, 4, or 5 stages of filtration. At least 4 stages is typically recommended for most applications. If you're on well water or an area with high levels of sediment, you may want to consider a system that has extra pre-filtration (5 stages). Four to five-stage RO systems will provide adequate filtration for most applications.

stages of a reverse osmosis water filter system
Number four

What about water hardness?
If your household's incoming water has a hardness level above 7 grains per gallon, you may need to install a water softener. An RO system is not designed to filter out high levels of calcium and magnesium that cause water to be hard. If your water is above 7 gpg hardness, water softener pretreatment will help preserve the life of an RO system and membrane, although not required.

Number five

Does an RO System Waste Water?
Similar to how we use water to wash our dishes, clothes or vehicles, RO technology uses water to clean the RO membranes as they process water. During the filtration process, RO systems typically use more water than the filtered water it produces. But because the system shuts down once the storage tank is full, water does not continue to run down the drain. Some systems, such as the PuROTwist PT4000T75 and Gro-75 1:1 are more water efficient than others. Normal RO systems have a 4:1 recorvery rate, but the PuROTwist PT4000T75 and Gro-75 1:1  achieve a 50% recovery rate or a 1:1 waste-water ratio.

Number six

How much water can a system produce?
Expect a GPD (gallons per day) production rate of 50% to 75% of system GPD rating. While it's true that no one really uses 50+ gallons of drinking water per day, the “50 GPD rating” is the speed that an RO system makes drinking water and produces a gallon of water per hour (with normal water pressure of about 60 psi). Thus, a 50 GPD-rated system will provide adequate production for the common household and will not cost much more than a lower GPD-rated system.

Number seven

Would you like RO water for your ice maker?
Add a refrigerator icemaker adapter kit to easily get RO water from your icemaker. You'll no longer need to buy a separate refrigerator filter. Check out tips on connecting to a fridge or ice maker.

Additional Considerations
Other considerations such as if you're on well water or city water, water pressure of your household water, etc. are also important. Learn more in our "What to Look for When Buying an RO System" article.

What size of RO System do I need?

A Reverse Osmosis system will typically operate under water pressure ranging from 40 to 100 psi and will generate 10 to 75 gallons (45-340 Liters) per day for point-of-use systems. Generally, a system's actual production rate is 50% to 75% of the system's GPD rating.

Understanding Reverse Osmosis Membrane GPD rating

  • RO systems are rated on how much water they can produce per day (gallons per day or GPD).
  • GPD ratings are based on tests performed under optimal water conditions (specific water temperatures and contaminant levels to achieve highest production rating).
  • Note that cold water reduces production rate by as much as half.
  • RO membranes become clogged with contaminants over time. Production will continue to decrease until filters and membrane are changed out.
  • Certain contaminants and levels of those contaminants can cause the filters and RO membrane to exhaust more quickly.
  • The price difference between lower production rate RO systems (24-36 GPD) and higher production rate RO systems (50-75 GPD) is typically minimal.

For residential use, we recommend a 50 GPD-rated RO system. The higher GPD system does not cost much more than a lower production rated system, and provides more than adequate production when water temperatures get cold during winter months, and as the membrane draws closer to the end of its' life (typically 24 months).


Where can I buy a quality Reverse Osmosis system or replacement filters and membranes?

We carry replacement filters and membranes for most major brands of Reverse Osmosis systems. We also have new Reverse Osmosis Systems available for purchase.

Why Buy from ESP?

At ESP Water Products, we're committed to staying at the forefront of innovation in the water filtration industry. We offer a wide variety of premium water filtration products from many of the leading brands in the industry. We're also proud to carry one of the largest online inventories of membranes, filters and replacement parts to keep your system in top shape.

Here are a few reasons you can shop with confidence at ESPWaterProducts.com

  • 25+ years of experience in water filtration & purification
  • We've researched the options out there to bring you the best
  • Competitive pricing on top-quality systems
  • We'll send filter replacement reminder emails to help maintain your system
  • One of the largest online selections of RO systems and replacement parts & membranes
  • Excellent customer support


Top-Selling Reverse Osmosis Drinking Water Systems

Microline TFC-400-ESP RO System 50 GPD TFC-400-ESP

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AXEON Solo I All-In-One 4-Stage 50 GPD RO System (211470)

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GRO 1:1 RO High Efficiency 75 GPD Drinking Water System (GRO-75GPD)

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  • Proven, High-Quality System
  • Compact, Space-Saving Design
  • Eco-Friendly System Conserves Water
  • Designer Chrome Faucet
  • Standard Chrome Faucet
  • Designer Chrome Faucet
  • High-Flow 3/8" Tubing to Faucet
  • High-Flow 3/8" Tubing to Faucet
  • High-Flow 3/8" Tubing to Faucet
  • 4-Stages of Filtration
  • 4-Stages of Filtration
  • 4-Stages of Filtration
  • Compact 3.2 Gallon Storage Tank
  • Standard 4.4 Gallon Storage Tank
  • Standard 4.4 Gallon Storage Tank
  • Airgap and Non-Airgap Faucet Connection
  • Airgap Faucet Connection
  • Non-Airgap Faucet Connection
  • 50 Gallons Per Day
  • 50 Gallons Per Day
  • 75 Gallons Per Day
  • Made in USA
  • Designed in USA, Made in China
  • Made in USA
  • Free Shipping
  • Free Shipping
  • Free Shipping

Reverse Osmosis Technical Tips

How to Change RO Filters

Learn how to replace your RO systems' filters and membrane with step-by-step instructions.
Read More>

How to Install a Reverse Osmosis System

Clear, concise instructions on how to install an under-sink reverse osmosis filtration system yourself.
Read More>

How to Connect an RO System to Fridge or Ice Maker

Tips for connecting your RO system to a refrigerator water dispenser or ice maker. Get step-by-step guidance for optimal results.
Read More>

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