How to Install an RO System + Reverse Osmosis Installation Diagram

Author: Rory Mullan - Published: 2021/07/08 - Updated: 2022/11/08

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So, you were horrified by the number of contaminants in your drinking water as per the sanitation report and decided to get your hands on a reverse osmosis system. Good decision. But, there’s still a major hurdle between you and clean drinking water: installation.

Typically, modern RO systems come with everything that’s required to install them, which is a blessing since it saves you minimum one trip to the hardware store.

However, even with the accessories included, installing a reverse osmosis system can be overwhelming, especially if you’re not good with tools. But that’s what we’re here for.

Here is our step-by-step guide on how to install a reverse osmosis system, along with some tips and tricks to make the job easier!


  1. Start by drilling a faucet hole in the countertop. Remember to position the faucet for convenience.
  2. Install the drain saddle on the drain line of the sink. You must position it above and with distance to the dishwasher discharge and garbage disposal.
  3. Shut off the cold water supply and open the faucet to relieve pressure.
  4. Install the feed valve adapter on the cold water line.
  5. Place the storage tank within 10 ft of the filtered water dispenser. You can use Teflon tape to wrap the threaded port at the top and then screw on the tank connector/valve.
  6. Connect the tubing to the RO module, water valves, tank valve, drain saddle, and RO faucet.
  7. Install all the pre-filters, the reverse osmosis membrane, and the post-filter.
  8. Check every connection for leaks as you open the feed water valve and the RO faucet. The storage tank valve must remain closed.
  9. Flush the system.
  10. Close the reverse osmosis faucet and open the storage tank valve.
  11. Fill and drain the tank 2 to 3 times.

Reverse Osmosis System Installation Diagram

Reverse Osmosis System Installation Diagram

Courtesy of BOS

Since it can be troublesome for some people to identify different components of an RO system, we took it upon ourselves to find a diagram showing the names of all parts and how they’re connected to each other.

Keep this picture in mind as you go through the instructions below so that you have a mental image of what goes where.

Where to Install an RO System?

The usual spot for a reverse osmosis system is under the kitchen sink, but it’s not the only place to install your new water purifier. If there are space constraints, you can install the system in a utility room or your garage.

For this, you need to make sure there’s a water line that connects to the kitchen sink. Here are some tips to keep in mind:

  • Do not install your reverse osmosis system in any place that experiences freezing temperatures.
  • Make sure it’s downstream of other water treatment systems, like a conditioner or a water softener.
  • Install the RO system on the cold water line.

How to Install a Reverse Osmosis System?

How to Install a Reverse Osmosis System Thumbnail

Now that we’ve got the basics out of the way, let’s get started with the actual installation process. All you need is some time on your hands, the accessories included in the package, and a few tools.

Do note that the instructions may vary slightly for different systems, but the standard process is pretty much similar. You can consult the instructions manual that came with your RO system or search for the model on YouTube to find a number of video tutorials for installation.

In case plumbing is involved, make sure you’re in compliance with your local and state codes.

Preparing for Installation

Make sure there’s sufficient space under the sink to keep a filter tank and module. Additionally, you also need to check for a cold water line since that will be used as the feed source.

Then, check if all components of your RO system are present.

Read the instructions manual to find out what should be included in the box. In this way, you’ll know if something is missing before you begin installation rather than at the fifth step.

Tools Required

When preparing for the system’s installation, it also helps to keep all your tools near you. Otherwise, you’ll have to move around a lot or waste time looking for things that are buried under other tools.

The tools you need include but are not limited to:

  • RO filter body + filter elements
  • Installation manual
  • Faucet
  • Storage tank
  • Power drill
  • Utility knife
  • Phillips head screwdriver
  • Adjustable wrench
  • Drill bit of the size specified by the instruction booklet
  • Installation kit
    • Connectors, tubing, drain saddle, filter housing wrench, storage tank valve

Step 1: Installing the RO Faucet

Before you do anything else, you need to install the RO faucet that will dispense the water cleansed by the reverse osmosis system. If you have already decided where to mount it, you can skip the next two paragraphs.

If not, you can drill a hole in the countertop or the sink. Do note you may have to use a specialized drill bit to ensure there’s no chipping or scratching on the sink.

The area where the faucet is to be installed should be flat and convenient enough to be reached by everyone. If there’s already an extra hole in your skin, you can mount the faucet there, too.

Using a center punch, mark the exact spot where you want to make the hole and grind away a sufficient amount of material to ensure the accommodation of the drill bit.

Then, drill a hole in the spot. Be slow if you’re approaching metal. If you want to make a ½” or ⅜” hole, start with a ¼” pilot hole. After creating the hole, remove any chips from the surface and clean any sharp edges.

Now, put the stem of the faucet through the hole and use nuts and washers to secure it from underneath. Lastly, install the quick connect fitting onto the faucet.

Step 2: Installing the Drain Saddle

Once you’ve installed the faucet, it’s time to install the drain saddle, which should be kept as distant as possible from the garbage disposal and dishwasher discharge.

Otherwise, it will clog and potentially damage the reverse osmosis filter system by bringing in contaminants and foul odors.

Plus, keep it far above the p-trap.

Start by drilling a quarter-inch hole in the side or the top of the drain line. You should never drill a hole in the bottom. Then, secure the drain saddle, ensuring the clamps’ hole is aligned with the pipe’s hole. Don’t overtighten.

Step 3: Installing the Feed Valve

It’s time to connect the cold water line with the RO system using the feed valve adapter. Start by turning off the water supply.

Then, open your regular kitchen faucet to release any pressure in the supply line.

Take off the cold water valve’s hose and install the feed water adapter of the RO system. Tighten it in place using a wrench. Keep the feed valve closed for the time being.

Now, connect the feed water adapter to the faucet hose and turn on the water supply. Keep in mind you might need an adapter for this step and for the installation of the new feed valve.

Step 4: Installing the Water Storage Tank

Before installing the water storage tank, you need to decide its position. It’s best to keep the tank a maximum of ten feet from the faucet so that you don’t lose any water pressure. A storage tank can be as heavy as 25 lbs when full, so place it accordingly.

Cover the tank’s threaded port with multiple layers of Teflon tape. Then, screw on the tank valve. It should be easy to thread, and you can do it with your hand.

While it makes sense to keep the storage tank upright, some models work perfectly even when kept on their sides.

Check the instructions manual before putting the storage tank on its side to save space in the kitchen.

Step 5: Mounting the RO System

Although it’s optional to mount the RO module, it’s a helpful way to keep things organized. However, keep in mind that you’ll have to replace the filters and reverse osmosis membrane[1] when they’ve exceeded their lifespans.

Moreover, you’ll have to perform other maintenance tasks too. Thus, there should be enough space under the unit.

Step 6: Connecting the RO System

Most RO systems have quick-connect settings. You just need to insert the tubes into the fittings and you’re good to go. To check the stability of a connection, gently tug it or try pulling it out and see if it sticks.

Here’s how to connect the tubes:

  • Tank-System: Connect the tubing to the filter system’s outlet port and the tank valve.
  • Feed Water Adapter-System: Insert the supply line into the feed water adapter from one end and tighten it in place using your hands. Push the other end into the corresponding port on the RO module.
  • System-Faucet: Connect the tubing to the system outlet port and the RO water dispenser.
  • System-Drain: Connect it to the RO module’s flow restrictor and drain saddle. You may have to cut the line to ensure water flow doesn’t get blocked.

Plus, if you cut the connections, it will make the water flow faster. However, it’s helpful to keep the extra tubing intact in case you ever want to relocate the system later on.

Step 7: Installing the Filter Elements

two water filter cartridges dropped in water

Read the instructions in the manual and insert the membrane and filters accordingly.

  • RO Membrane: Remove the cap of the membrane housing and insert the cylinder into it. Make sure it’s completely in before putting the cap on again. The O-rings must not be loose.
  • Remaining Filter Elements: Start by removing the filter housings. Insert each filter cartridge assemble the housings again. Tighten them in place using the filter housing wrench.

When installing or replacing filters, follow the order of placement as per the instructions manual. The pre-filters go first with the RO membrane after them. Finally, there’re the post-filters.

Step 8: Starting It Up

You’re almost done. Now, you just need to start the reverse osmosis system by following these steps:

  1. Open the RO water dispenser and the feed water adapter. However, the storage tank valve should be closed in this step. If you hear gurgling, don’t worry since it’s just air being released.
  2. Check if there are any leaks in the system.
  3. In ten to fifteen minutes, you should see water dribbling from the dispenser. If the initial output has a dark color, no need to worry since the system is just flushing out carbon fines.
  4. Now, turn off the faucet and let the storage tank fill by opening the valve.
  5. The tank will fill within several hours. Once the tank is full, there will be no noise of water going down the drain. That’s when you need to open the RO faucet and flush the unit.
  6. When water flow from the dispenser slows down, it means the tank is empty now. Again, close the RO faucet and let the storage tank refill.
  7. Flush one more time.

Manufacturers often advise you flush a new RO system a couple of times before using it.

Hiring a Professional Installer

If DIY-ing the reverse osmosis system installation is too much for you, go ahead and call a plumber to take on the task. The cost of installation is based on the type of RO system:

  • Under Sink: $150 to $400 – If you have some technical expertise, you can do this yourself in about one to two hours.
  • Countertop: Free – These RO systems are the best if you do not want to pay a plumber or spend your weekend trying to DIY an installation. They just need to be connected to a kitchen faucet and are easily portable.
  • Whole House: Over $500 – The installation of a whole house reverse osmosis water filter system is quite complex. Therefore, it’s more expensive and time-consuming. The exact cost will differ, depending on the type of system and the size of your home.

Where to Find a Plumber?

If you don’t know a local professional, search for one online. Yelp[2], Google Reviews and HomeAdvisor are great places to start.

Before choosing a plumber, make sure you’ve received estimates from a couple of providers. It will help you find a reasonable option. Also, ask for their references to make sure they’re fit for the job.


In conclusion, the installation of a reverse osmosis system can be challenging but is nowhere near impossible. In our opinion, it makes a great DIY project.

The best place to install a standard system is under your kitchen sink.

Prepare the installation by collecting all the necessary tools beforehand. Also, check if your RO system package contains all the supplies you need.

Then, all you need to do is follow the instructions in the installation booklet. For reference, you can check our instructions above.

We estimate around 1 to 2 hours from start to finish.

Further Reading


Meet Rory Mullan

Rory Mullan Rory has joined the Water Masterz team as a contributing writer. He has covered all sorts of topics in the last several years.

Outside of his writing work, Rory enjoys photographing the Irish landscape and making music!

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