Reverse osmosis (RO) water filters have become one of the most popular upgrades for homeowners looking for clean, great-tasting, purified drinking water. They remove contaminants like chlorine, lead, sediment, dissolved solids, and even some chemicals that traditional filters miss.
Whether you’re upgrading your kitchen or replacing an old system, here’s a clear, step-by-step guide explaining how professionals install under-sink RO systems—the most common type in North America homes.
⭐ What You Need for Installation
Most RO systems come with all necessary parts, but you may also need:
- Adjustable wrench
- Drill + drill bits
- Screwdriver
- Teflon (plumber’s) tape
- Bucket or towel
- Utility knife
- Optional: hole saw (for faucet installation if no existing hole)
1. Plan Your Installation Area
Most RO systems fit under the kitchen sink, but you need room for:
- The filter assembly
- The storage tank
- The dedicated RO faucet
Make sure the area is clear and dry. If space is tight, consider removing the cabinet doors for better access.
⭐ 2. Install the RO Faucet
Most RO systems include their own drinking-water faucet.
If your sink has an extra pre-drilled hole (often used for soap dispensers), you can use that. If not, you’ll need to drill a new one.
How pros install the faucet:
- Clean the hole or drill a new ½”–1″ hole (depending on faucet size).
- Place the faucet, gasket, and trim in position.
- Tighten the mounting nut underneath the sink.
- Connect the faucet tubing according to the manufacturer’s instructions.
Pro Tip:
If drilling into a stainless-steel sink, go slow and use a lubricant. For stone countertops (granite/quartz), drilling should be done with a diamond bit—or by a pro to avoid cracks.
⭐ 3. Install the Drain Saddle
The drain saddle allows wastewater to exit the RO system properly.
Steps:
- Choose a section of the vertical drainpipe—not the horizontal section—to prevent noise and backflow.
- Drill a ¼” hole in the drainpipe.
- Place the drain saddle over the hole and secure it with screws.
- Make sure the opening of the saddle aligns perfectly with the drilled hole.
Mistake to Avoid:
Don’t overtighten the drain saddle—this can deform the pipe and cause leaks.
⭐ 4. Install the Feed Water Valve
This valve connects the RO system to your cold-water supply line.
How it’s done:
- Turn off the cold-water supply.
- Disconnect the existing cold-water line from the faucet.
- Install the feed valve between the shut-off valve and the faucet line.
- Use Teflon tape to seal any threaded connections.
- Connect the RO system’s feed line to the new valve.
Once installed, your RO system now has a dedicated water source.
⭐ 5. Mount the RO Filter Assembly
You can mount it to the cabinet wall or let it sit upright under the sink.
Tips from the field:
- Leave enough slack in the tubing for easy filter changes.
- Avoid mounting too close to the garbage disposal or water heater lines to prevent vibration or damage.
⭐ 6. Place and Connect the Storage Tank
- Wrap Teflon tape around the tank’s threaded nipple.
- Install the tank valve.
- Place the tank under the sink (upright).
- Connect the tank tubing to the system.
The tank typically holds 2–4 gallons of purified water.
⭐ 7. Connect All Tubing
Most RO systems use color-coded tubing:
- Red – supply line (to the feed valve)
- Black – drain line
- Blue – pure water line (to the faucet)
- White – tank line
Push each line firmly into its quick-connect fitting. Tug gently to ensure a secure connection.
⭐ 8. Turn On the System and Check for Leaks
- Turn on the cold-water supply.
- Open the RO faucet.
- Allow the system to fill the tank (usually 2–3 hours).
- Check all connections for leaks.
- Drain the first tank completely—the initial water is used to flush the filters.
After the first flush, your RO system is ready for use.
⭐ Maintenance Tips for RO Systems
To keep your RO system running at peak efficiency:
- Replace pre-filters every 6–12 months
- Replace the RO membrane every 2–3 years
- Sanitize the system annually
- Replace post-filters as recommended by the manufacturer
Professional servicing can extend the lifespan of the system and ensure optimal water quality.
Should You DIY or Hire a Professional?
Installing a reverse osmosis system can be straightforward—but challenges arise when:
- There’s no hole in the sink for the RO faucet
- Plumbing lines are outdated or corroded
- The drain line is hard to access
- The system has multiple specialty filters
- Space under the sink is cramped
A professional handyperson can install the system cleanly, without leaks, and in compliance with local plumbing standards.
Need a Reverse Osmosis System Installed? We Can Help.
We install RO systems for homeowners across North America with fast, clean, reliable service. Whether you’ve bought a system from a store or online, we ensure it’s installed correctly and safely.
📞 Book your RO installation today
💧 Clean, great-tasting water
🔧 Professional installation
⚙️ No leaks, no mess
🏠 Guaranteed workmanship
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