You don’t need a professional to install a reverse osmosis system. If you’ve bought an RO system or are planning to buy one soon, you can set it up yourself with the necessary tools.
It takes about 2-3 hours to install most under-sink RO units with most of that time spent drilling holes for the faucet and the drain line.
Because they know most buyers prefer DIY installation, manufacturers have made their systems very straightforward to set up.
Most RO units come with color-coded parts, quick-connect fittings, and pre-assembled parts.
Below is a detailed guide on how to install a reverse osmosis system under your sink. Countertop systems don’t require any installation, so we are not going to cover those.
As with any other machine, always read the user manual before you do anything.
Check that all the parts are present. If anything is missing or appears faulty or broken, contact customer support.
Familiarize yourself with all the parts and gather all the tools you’ll need.
Where to Install a Reverse Osmosis System
The ideal location is under the sink. It’s the easiest place to connect water from the cold water line and direct the wastewater through the drainpipe.
But that’s not the only space you can install an RO unit. If your under-sink area is too small, you can also set it up in the basement or garage and direct the purified water to the faucet on the sink.
But you might need to install a booster pump to ensure water reaches the faucet with adequate pressure.
Do not install the RO system in a place where freezing conditions are possible and do not install it outside where it will be exposed to the elements.
What You’ll Need
- The user manual.
- The RO unit and installation kit (double check against the manual to make sure all parts are present).
- Power drill.
- A ½” or 3/8” drill bit depending on faucet size. You’ll also need a ¼” drill bit for the drain line.
- A utility knife or pair of sharp scissors.
- Teflon tape.
- An adjustable wrench.
- A center punch.
Step-by-Step Installation Guide
Assemble the Filters
This is not necessary if your filters come pre-assembled.
If not, first make sure all filters are present and learn which types of filters the system uses.
Following the user manual, insert the filter cartridges into their housings and then attach them to the filter mount.
Make sure you insert the right cartridges into the right housings.
Some systems like Home Master have the cartridges and housing as one unit. If that’s the case with your system, you need to attach each filter to the mounting.
Check that the filters are in the right order.
With the filters assembled, it will be easy to mount them on the wall under the sink when its time.
Install the Faucet and Drain Saddle
Before you begin the installation, turn off the cold water line and drain it by turning on the faucet until it runs empty.
We’ll start with the most time-consuming steps so that all you are left with is making the final connections.
Installing the Faucet
- Check if the sink already has a spare hole, perhaps one reserved for a soap dispenser or sprayer. If there’s one and it’s compatible with the new faucet, no need to drill a new hole. If there isn’t a spare hole, you’ll need to drill a new one.
- Make sure you have the right drill bit for your sink material to prevent scratching or to chirp the sink.
- Use a center punch to mark the exact location on the sink. When selecting a location, make sure the drill won’t damage anything underneath.
- For porcelain and metal, sinks start by carefully drilling through the porcelain with a ¼” masonry drill bit. When metal shows, switch to a metal drill bit.
- Use a larger bit to enlarge the hole to ½” or 3/8” depending on faucet size.
- For metal sinks, drill through with a metal drill bit. Start with a ¼” pilot hole then expand to the required size.
- If you are installing an air gap faucet, you’ll need a 1¼” or 1½” hole, which requires special tools. Ask a pro to drill the hole for you.
- Position the faucet in the hole. The faucet base and washer should be above the hole while the nut and washer should be tightened onto the faucet stem from below the sink.
- Make sure that the faucet is firmly in place.
Installing the Drain Saddle
Before you put the drill away, you’ll need to make a ¼” hole for the drain line.
Select a position away from the garbage disposal and dishwasher discharge to avoid contamination and clogging up the drain.
It should also be at least 6 inches above the P-trap.
Drill the hole on top or side, not at the bottom. Secure the drain saddle around the pipe, being careful not to overtighten.
Making the Connections
The remaining part is easy and quick. You need to connect the right tubes in the right places.
The tubes are color-coded to make it easier to know where they go. Reference your manual for what different colors mean.
Most RO systems use quick connect push fittings, which are easy to work with and don’t require any tools.
- Remove the cold water line and attach the T-connector to the cold water outlet. If the T connector doesn’t fit, check if there’s an adaptor included that will fit. Most RO units come with multiple adaptors.
- Attach the cold water line and the RO tubing to the T connector.
- Before you make any more connections, mount the filter frame on the wall under the sink. Some filters don’t need to be installed; you can place them on the floor.
- Place the reserve tank on the floor. Apply about six layers of Teflon tape around the tank port and then tighten the tank valve onto it. If the tank doesn't fit vertically under the sink, you can place it on its side.
- Finish all connections. You should have tubes running from the inlet valve to the inlet port of the RO system, from the RO system to the tank, from the RO system to the drain saddle and from the tank to the RO faucet. Check the color codes in the manual to make sure every tube goes to the right place.
Make sure tube connections are secure. Push the tube into the fitting until it doesn’t go any further. Tug slightly at the tube to make sure it is secure.
Finish Setup
Double check that everything is connected properly then turn on the cold water.
Look for leaks around connections.
Next comes one of the most important step: flushing the system. Don’t forget it.
The initial RO water is not ready for drinking. Let the tank fill and then empty it 2-3 times (check the manual for the specific number).
After that, the water is ready for drinking.
