How to Install a Reverse Osmosis Water Filtration System

Installing a reverse osmosis (RO) water filtration system can tremendously improve your home’s water quality by reducing contaminants, odors, bad tastes, and sediment. While RO systems require some plumbing work, the installation process is straightforward if you have some DIY skills. Here is a step-by-step guide on how to install a reverse osmosis system in your home.

Choosing an RO System

The first step is selecting the right reverse osmosis system for your needs. Here are some factors to consider when shopping for an RO system:

Filtration Stages

RO systems contain multiple filtration stages that work together to purify water. While basic systems have three stages, more elaborate systems can have up to seven stages:

Stage 1) Sediment filter – removes sand, silt, dirt, rust particles
Stage 2) Carbon prefilter – removes chlorine, odors, organic contaminants
Stage 3) RO membrane – removes salinity, minerals, metals, microorganisms
Stage 4) Carbon postfilter – polishes taste, removes volatile organic compounds
Stage 5) UV light – destroys microorganisms, bacteria, viruses
Stage 6) Mineral filter – adds healthy minerals back
Stage 7) Alkaline filter – increases pH

The more stages a system has, the more thorough the filtration will be. A 5-7 stage system removes the widest array of impurities.

Daily Production Rate

The daily production rate indicates how many gallons of filtered water an RO system can produce per day. This depends on the size and efficiency of the RO membrane. Standard residential systems produce 50-100 gallons per day, which is suitable for 1-2 people. Larger families may need a system with a 200+ gallon daily rate.

Storage Tank Size

RO systems use a storage tank to hold the filtered water. The larger the tank, the more filtered water is available on demand. Typical tank sizes are 2-3 gallons, but larger 4-5 gallon tanks are better for big households.

Feed Water Source

RO systems are designed for either municipal water or well water sources. Well water systems have extra pre-filters to handle dirt, silt, and other debris commonly found in wells. Make sure to get the system designed for your water source.

Installation Type

RO systems come in two installation types:

Under Sink – The system mounts under the sink and delivers water through a separate faucet. Best for renters or easy access to filters.
Whole House – The system integrates into the main water line to filter all faucets. Ideal for filtering all household water. Requires professional installation.

Under sink systems are the most popular choice for DIY installs.

Gathering the Required Plumbing Parts

Once you’ve selected an under sink reverse osmosis system, gather the additional plumbing parts needed for installation:

Feed water adapter – Attaches to cold water line to feed water to the RO system
Drain saddle – Mounts on drain pipe to drain wastewater from RO
RO faucet – Special faucet that dispenses filtered water
Tubing – Food-grade tubing to connect system components
Fittings – John guest fittings, union connectors, tube inserts, etc.
Water block – Optional shut off valve for feed water line
PEX crimp rings – For securing tubing connections
Wrenches – For tightening fittings
Drill + bits – For drilling holes for faucet & drain saddle
Variable speed drill – For drilling hole in sink for faucet

Many RO systems come with some of these parts, but you’ll likely need to purchase additional fittings, tubing, tools, etc.

Water Supply Considerations

Before installing the RO, inspect under the sink and determine:

Cold or hot water supply? – RO systems should always connect to the cold water line.
Flexible supply lines? – Braided stainless steel supply lines simplify connections.
Shut-off valves? – Existing shut-off valves allow isolating water when needed.
Sink sprayer? – Sprayer hose may need disconnected for faucet installation.
Pipe materials? – RO tubing connects easiest to PEX or flexible copper lines.
Garbage disposal? – The drain saddle location must be before any garbage disposal.

Address any issues before proceeding with installation. Having flexible water lines, shut-off valves, and easy access to piping simplifies installation.

Step 1 – Mount Storage Tank and RO System

The first step is mounting the storage tank and RO system under the sink:

Locate a suitable spot under the sink to mount the RO system and storage tank. The system should be easily accessible for future filter changes.
Use the included mounting bracket to hang the storage tank on the cabinet wall toward the back. The tank should hang vertically upright.
Similarly, use the mounting bracket to hang the RO system on the cabinet wall toward the front. Leave space between the tank and system for future access.
Make sure the tank and system hang securely and their weight is supported properly by the cabinet wall.

Step 2 – Install Drain Saddle

The drain saddle assembly is installed next:

Identify the drain pipe under the sink where you want to install the saddle. Make sure the location is near the RO system but before any garbage disposal or tailpiece from the main sink drain.
Hold the saddle against the drain pipe oriented correctly for the flexible drain tubing connection. Make sure the saddle won’t interfere with pipes or provisions for the faucet.
Use a pencil to trace a circle around the inside of the drain saddle end. This marks where to cut the hole in the drain pipe.
Remove the saddle and drill a 1⁄4” hole in the center of the circle. Use a drill bit suitable for the pipe material. Go slow to avoid cracking plastic pipes.
Use a jigsaw to cut along the traced circle to create the hole for the saddle. A Dremel rotary tool also works well. File the cut edges smooth.
Apply silicone sealant or plumber’s putty around the saddle’s drainage outlet.
Mount the drain saddle assembly over the hole so it aligns properly.
Secure the saddle tightly using the included bolts and washers. Don’t over-tighten.
Once secured, attach the flexible 1⁄4” drain tubing to the saddle using the compression nut. Adjust the tubing so it routes upward toward the RO system.

Step 3 – Install the Faucet

Now it’s time to tackle the filtered water faucet installation:

Choose an appropriate spot on your sink, counter, or nearby wall for the RO faucet. It should be placed conveniently within reach near the main faucet.
Check below to ensure there is enough clearance for the faucet and that it won’t interfere with drawers, existing plumbing, etc.
Turn on the main faucet and let the water stream hit the desired RO faucet location. This lets you visualize the precise spot. Turn off the main faucet once marked.
Place painter’s tape on the sink where the hole will be drilled. This prevents scratching the sink surface.
Use a variable speed drill with a 1⁄2” drill bit to drill a hole through the sink for the RO faucet. Go slow with ceramic sinks to prevent cracking.
Insert the faucet shank through the sink hole. Make sure the rubber gasket properly seals the opening.
Slide the metal escutcheon plate over the shank and orient the faucet correctly.
Install the locking nut from below the sink and tighten it securely using an adjustable wrench. Don’t over-tighten.
Attach the tubing adapter piece to the bottom of the faucet shank using included wrench. This connects the tubing.

Step 4 – Install Feed Water Adapter

The feed water adapter taps into the cold water line and diverts water to the RO system:

Locate the cold water supply line and determine the best place to install the feed water adapter and shut-off valve (if using).
Shut off the cold water supply using the angle stop shut-off valve under the sink or the main house valve.
Attach the provided saddle clamp or tee fitting at the chosen location on the cold water pipe.
Secure tightly using the screws on the saddle clamp. Go slowly to avoid cracking plastic piping.
Screw in the feed water adapter into the saddle clamp or tee. Use thread sealant tape to prevent leaks.
If using a shut-off valve, attach it to the adapter. The arrow should point toward the RO system.
Once secured, turn the water back on and check for leaks. Tighten any leaky connections.

Step 5 – Connect System Components

With all the key components in place, it’s time to connect the RO system into an integrated whole:

Attach tubing between the RO faucet and the RO system using compression fittings. Cut the red tubing to the needed length using tubing cutters.
Connect tubing between the drain saddle and the RO system using provided compression fittings. Cut the black tubing to size.
Connect the yellow tubing from the feed water adapter to the RO system’s inlet. Cut to size. Use a union connector if the tubing doesn’t reach.
Attach blue tubing from the RO system outlet to the top of the storage tank. Cut to needed length.
Install chlorinating tablets and filters into the RO system per the manufacturer’s instructions.
Turn on the feed water and check for leaks throughout the system. Tighten any leaky compression fittings.
Flush the system and lines per the manufacturer’s instructions. This clears any residual manufacturing chemicals, carbon dust, or sediment.
Once flushed, the system is ready for use! Open the RO faucet and enjoy purified water.

Step 6 – Adjust Storage Tank Pressure

The final step is properly pressurizing the storage tank:

Shut off the RO faucet and allow the tank to fill completely undisturbed. This allows it to pressurize fully.
Once the tank is filled after several hours, turn off the feed supply valve. This isolates it.
Open the RO faucet to release pressure. Once flow stops, it is empty.
Use a bicycle tire pressure gauge to check the pressure at the tank’s air valve. Standard pressure is 5-7 PSI.
If needed, add or release air using a bicycle pump/needle nose until the proper pressure range is reached.
Turn feed valve back on. Tank pressure is now optimized for maximum performance.

Troubleshooting Common RO Problems

If issues arise after installation, here are solutions to the most common RO problems homeowners experience:

Low water production

Replace filters if they are clogged or expired
Check tank pressure and re-pressurize if needed
Inspect and clean RO membrane as scale may be reducing flow
Ensure feed water valve is fully open

Milky or cloudy water

Drain tank fully and allow to refill over 24 hours
Replace carbon postfilters as they may be saturated

Odor or bad tastes

Replace all filters if over 6 months old
Sanitize entire system with chlorine bleach solution
Ensure sink drain has proper p-trap and is filled with water

Leaks in tubing or fittings

Release pressure and open RO faucet before addressing leak
Check and tighten compression fittings to eliminate leaks
Cut off and re-install leaky tubing sections if needed

Low pressure at faucet

Check storage tank pressure and re-pressurize to 5-7 PSI if needed
Replace sediment prefilter if clogged or dirty
Inspect RO membrane for fouling or scaling

Following this comprehensive guide, you should feel confident tackling a reverse osmosis system installation in your home. While it takes some plumbing skills, the benefits of enjoying purified water from every faucet in your home make installing an RO system a worthwhile DIY project.

Frequently Asked Questions

How long does it take to install an under sink RO system?

Installing an under sink reverse osmosis system typically takes 3-5 hours, depending on the existing plumbing and complexity of the installation. Gathering supplies and materials adds time as well. With practice, an experienced DIYer can install an under sink system in 2-3 hours.

What tools do I need to install an RO system?

Common tools needed are adjustable wrenches, Phillips and flat head screwdrivers, hole saw drill bits, a power drill, tubing cutter, razor blade, Teflon tape, channel lock pliers, silicone sealant, plastic tubing cutter, and a jigsaw or rotary tool if modifying drain piping.

Where should the RO drain saddle be installed?

The drain saddle should be installed above the p-trap on the vertical or horizontal tailpiece. Never install the drain saddle downstream of the garbage disposal as debris will clog it.

Can I connect an RO system to my hot water supply?

Reverse osmosis systems should always be installed on the cold water supply. The hot water will damage RO membranes and other filter components.

How do I get filtered water to my refrigerator?

Use a T-fitting and extra tubing to split the line supplying the RO faucet. Run tubing from the T-fitting to refrigerator’s water line inlet. This provides filtered water to both.

Why is my tank losing pressure?

Storage tanks lose pressure over time through the bladder or diaphragm. Check pressure every 6 months and re-pressurize the tank as needed to maintain optimal RO efficiency.

How often should I change RO filters?

Most manufacturers recommend replacing prefilters every 6-12 months and the RO membrane every 2-3 years. Annual filter changes keep the system operating at peak performance.

Conclusion

Installing a reverse osmosis water filtration system enables you to enjoy clean, pure water for drinking, cooking, and ice-making. While it takes some DIY plumbing skills, this guide provides the key steps for proper under sink RO installation. The benefits of having filtered water on demand makes learning how to install an RO system a worthwhile home improvement project.