RO installation

Reverse Osmosis Water System DIY Installation How-To


    So, you’ve decided to add an RO water filter system to your home, because you don’t want to be exposed to those nasty tap water contaminants any longer. You found a great model online that suits your needs and you purchased it a couple of days ago. This morning the system arrived in a big heavy box. Although you haven’t had the time to do the installation, out of mere curiosity you opened the package to take a first glance…

    What a shock! You didn’t anticipate that a single system would include that many different parts. There is a tank, different filters, a membrane, an extra faucet, tubing of different colors, and a couple of smaller connectors and valves.

    Now all you can think about is that hopefully you have the expertise to set everything up correctly – after all, you are not a plumber! But considering the costs for hiring a professional that would add to the expenses of the filter system itself, it’s a priority for you to do the installation on your own.

    Don’t worry. We’ve got you covered! In this article we will provide you with all the resources you need for a trouble-free installation process.

    On this page you will learn:

    Reverse Osmosis System Installation – Under Sink Systems

    It’s time to learn how you can hook up your new reverse osmosis under sink system the right way. With a little preparation and the necessary tools, you don’t have to be a professional plumber to set up everything correctly.

    Also, every system comes with detailed setup instructions. If that isn’t enough, you can find numerous helpful installation videos from different manufacturers on YouTube.

    Before You Start, Carefully Read All Steps and Safety Guidelines in Your System’s Installation Manual. If in Doubt About Your Next Step, Consult the Manufacturer.

    Installation Diagram

    Schema RO Systems

    Step by Step

    Individual steps may vary from product to product and depend on your specific plumbing setup. Therefore, the following installation details are given as a general approach.


    Before you even purchase an RO system, it’s a smart idea to make sure that there is enough space under your kitchen sink for the tank and the filter module. So, look up the specifications of your favorite system and perform some measurements.

    You also need to make sure that there actually is a cold water line you can draw the feed water from (which, of course, is nearly always the case).

    Once the system has been delivered, unbox it and double check that all components fit in their desired location. This way you already know beforehand if you need to make some adjustments to the drain or other pipes before the installation itself can start.


    Identify and assemble all necessary tools and components. Having everything you need lined up before you start the installation can save you from a lot of frustration. The following list makes no claim for completeness:

    • Installation manual
    • RO module
    • Water storage tank
    • Faucet
    • Installation kit including color coded tubing, filter wrench, stop connector, tank valve, faucet connector, drain saddle, membrane
    • 1/4″ drill bit
    • Screwdriver
    • Tubing cutter
    • Utility knife
    • Adjustable wrench
    • Towel

    Faucet Installation

    We begin the installation with setting up the RO faucet that will soon provide great tasting, filtered drinking water. Most RO faucets have a connection with a 1/4″ or 3/8″ tubing fitting.

    First of all, you have to decide where you want to place the faucet, which is an easy decision, if your sink already has an extra hole for the mounting. If it doesn’t, you have to drill a new hole into the sink or the countertop. Depending on the type of material, you may require a special type of drill bit here.

    Gently grind away enough surface material to safely accommodate the 1/4″ drill bit. Now carefully drill the hole and go extra slow when you are about to penetrate any metal (a drop of oil in the hole can work wonders).

    When you are done, remove any remaining metal chips that could damage the surface. Place the faucet stem inside the hole and secure it with a nut from the bottom. Then attach the quick connect fitting to the bottom of the faucet and tighten it with a hand wrench.

    faucet installation

    Drain Saddle Installation

    The next step is to install the drain saddle or drain line adapter to the drain line. The saddle/adapter has to be placed above and as far away as possible from the dishwasher discharge and garbage disposal to protect your RO system from potential contamination and fouling.

    Drill a 1/4″ hole into the top or the side of the drain line (never the bottom). Put the drain saddle in place and fix it with bolts. Be careful to not over tighten anything.

    Feed Valve Installation

    In step three, we install the inlet feed valve, which connects the RO system to the cold water line of the existing sink.

    First, turn off both the cold and hot water supply. If the valves are inoperable, you have to shut off the whole water supply to your home. Next release the pressure in the water lines by opening the faucet. Then remove the tubing from the cold water valve and install the new feed valve. Make sure to turn the feed valve off.

    Attach the cold water tubing back to the new valve and turn the cold and hot water supply back on.

    Water Storage Tank Installation

    You should place the storage tank within 10 feet of the drinking water faucet to not lose any significant pressure. And don’t forget that a tank can weigh up to 30 pounds when filled up to the top.

    By the way: With many systems, the storage tank can also be placed on its side without affecting filtration performance. This comes in handy, if you lack sufficient space under your kitchen sink.

    Before putting it in position, it is often advisable to wrap about 5 winds of Teflon or plumber’s tape around the threaded port on top, before attaching the tank valve or tank connector itself. The connector should thread on easily and only needs to be hand tight.

    RO Module Connection

    Now it’s time to install the RO module itself using the color coded tubing. Keep in mind that trimmed connections will maximize water flow rate. On the other hand, leaving some extra tubing will come in handy, if the system ever needs to be moved somewhere else.

    Apart from this, there may be water residues in the tubes if the system was tested by the manufacturer, so keep a towel at hand to wipe it up.

    • Orange feed water line – Push the orange supply line onto the feed valve of the existing sink line faucet supply (tighten the nut a half turn past hand tight) on the one end and to the feed port of the RO module on the other. Also, cut the line if necessary so that it won’t get kinked.
    • Green tank line – Connect the green line to the pressure tank valve and the outlet port of the filter system.
    • Black drain line – Connect the black line to the previously installed drain saddle and the flow restrictor of the RO module. If possible, cut the line so that water can flow downhill without loops.
    • Blue faucet supply line – Connect the blue line to the quick connect fitting of the RO faucet and to the post filter outlet port.

    As with the storage tank, many RO modules can be mounted both vertically and horizontally. When positioning, take into consideration that every once in a while you need to access the module for filter replacements and other maintenance tasks.

    Filter and Membrane Installation

    Once all the connections are made, place the different filters and the RO membrane into their housings according to the instructions provided. Usually, the first filter will be the sediment filter, followed by carbons filter(s), and lastly the membrane.

    To put the membrane in place you have to remove the housing cap and carefully push the cylinder into the socket until completely in. Then put the housing cap back on.

    Starting the System


    Finally it’s time to start the system! Here is how:

    1. Turn on the feed water valve, but keep the storage tank valve closed, so no water can enter the tank.
    2. Check all fittings for leaks. If you can’t make out the source of leakage, maybe our RO troubleshooting guide can help you out!
    3. Once water dribbles out of the faucet after about 10-15 minutes, close it and open the storage tank valve to allow the tank to fill. By the way, there is no reason to worry in case the first trickle of water is brownish in color. This is just the water flushing out carbon filter fines.
    4. Filling the tank will take anywhere between 6-10 hours. As soon as it’s full, you will no longer hear water running down the drain. This is when you have to open the RO faucet to flush the whole unit.
    5. When the water is again down to a dribble, this means that the storage tank is now empty. Close the faucet and let the tank refill.
    6. Once the tank is full, flush the system a second time by turning the faucet back on.

    It is recommended to flush a new RO system 2-3 times prior to use. Once you’ve done that, the installation is completed and your water is ready for drinking.

    Full Installation Video

    Reverse Osmosis System Installation Cost

    A large proportion of customers choose to install their RO system themselves. However, an even larger part prefers to turn to an expert, because these people are worried about not having the right tools and knowledge to complete the task.

    If you, too, are in doubt about your manual skills, we recommend you to call a local plumber to do the installation for you.


    How much the installation of an RO system costs, depends first and foremost on what kind of system you want to have installed. We distinguish between:

    • Countertop systems, Costs: $0 – A countertop system can be fitted to your kitchen faucet and removed from it within seconds. The main benefit here is portability as no ‘real’ installation is required. → learn more
    • Under sink systems, Costs: $100-$300 – As we have seen, standardized under sink systems require proper installation; something you can do yourself within 1-2 hours of your time, if you are technically skilled. The outsourcing costs should range somewhere between $100 and $250, but should not exceed $300. This estimate includes costs for labor, equipment, materials, and waste disposal. If any component in your home has to be modified or repaired, costs are likely to increase.
    • Whole house systems, Costs: $500+ – It’s really hard to estimate installation costs for whole house RO water filter systems, as they are more complex. One thing is for certain, though, the likelihood that you are capable of installing one in your home all by yourself is small. Instead, we recommend you to hire a professional plumber who will do it for you. This person does not only have to do the installation, there are additional components needed, like valves and tubing, that will add to the costs. To get an estimate, the best approach is to talk to some plumbers in your area. Also, if you are looking for a whole house system to add to your home, follow this link:

    What to Look Out For

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    If you don’t already have a plumber in mind whom you trust, checking out local reviews online is a great starting point. Popular sites you can use are:

    Furthermore, it is likely that you can save a lot of cash, if you talk to more than one plumber and let them know that you already have purchased a system, but need help with the installation. Ask for their expertise, references, and a cost estimate.

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    If you have any questions or thoughts about how to install an RO system, please don’t hesitate to leave a comment below!

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