Reverse Osmosis System Installation Guide

Now what?

Installing an RO system sounds intimidating. But it’s not as hard as you think. With basic tools and an afternoon, most homeowners can do it themselves.

Let me walk you through this reverse osmosis system installation guide from start to finish. No plumbing degree required.

Before You Start: What You’ll Need

Gather these items before you begin. Nothing worse than stopping mid-installation to run to the hardware store.

Tools you’ll need: Adjustable wrench, bucket or towel (for drips), drill with 1/4 inch and 1/2 inch bits (for drilling a faucet hole if needed), utility knife, Teflon tape (usually included), flashlight (for looking under the sink).

Parts that should be in the box: RO membrane and filter cartridges, filter housings and wrenches, storage tank, dedicated faucet, tubing and fittings, saddle valve or feed adapter, instructions (keep these handy).

Time needed: 2 to 4 hours for a first-time installer. Less if you’ve done it before.

Follow this reverse osmosis system installation guide step by step and you’ll be drinking great water by dinner time.

Step 1: Clear Out Under Your Sink

Empty everything from the cabinet under your kitchen sink. Cleaning supplies. Trash can. That collection of old sponges. Everything.

You need room to work. RO systems take up space. Most under sink cabinets are cramped. Removing everything gives you elbow room and prevents you from knocking things over.

Also, put down a towel or small bucket. You’ll likely spill a little water. It’s normal. Just be prepared.

Take a photo of your existing plumbing with your phone. This helps if you need to remember how things looked before you started disconnecting things.

Preparation is the key to any good reverse osmosis system installation guide. Don’t skip this step.

Step 2: Install the Dedicated Faucet

Your RO system needs its own faucet. Most systems include a small chrome or brushed nickel faucet that sits next to your main kitchen faucet.

If you have an existing soap dispenser or sprayer hole: Remove it. The RO faucet will fit in that same hole. Easy.

If you have no extra hole: You’ll need to drill one. Measure carefully. Drill from the top of the sink or counter. Use a 1/2 inch bit for most faucets. Check your instructions for exact size.

If you’re renting or can’t drill: Some systems can mount the faucet on the counter next to the sink. Not ideal but possible. Or use an air gap faucet that mounts through the sink deck.

Once the hole is ready, drop the faucet through. Tighten the locking nut from underneath. Don’t overtighten — you can crack the faucet base.

Attach the 1/4 inch tubing to the faucet. Hand tighten the compression fitting. Set the tubing aside for now.

Every proper reverse osmosis system installation guide starts with the faucet. Get this right and the rest flows smoothly.

Step 3: Mount the RO System

Most RO systems come with a metal bracket for wall mounting. Find a spot on the cabinet wall under your sink. Make sure the system will fit without touching pipes or the garbage disposal.

Hold the bracket in place. Mark the screw holes. Drill pilot holes if needed. Screw the bracket to the cabinet wall. Hang the RO system on the bracket.

If you can’t mount to the wall, you can stand the system on the cabinet floor. Just make sure it’s stable and won’t tip over when you open the cabinet door.

The system should be accessible for filter changes. Don’t bury it behind cleaning supplies. You’ll thank yourself later.

Step 4: Connect to the Cold Water Line

This step intimidates most people. Don’t let it. It’s simple.

Find the cold water line under your sink. It’s usually the right side pipe. Turn off the cold water shutoff valve. Open the cold water faucet to release pressure. Have your towel ready for drips.

Option A: Saddle valve (included with many systems). Clamp the saddle valve onto the cold water pipe. Turn the handle to pierce the pipe. Stop when water drips out. Attach your tubing. This is the easiest method but not legal in all areas. Check local codes.

Option B: Feed adapter (better method). Disconnect the cold water supply line from the shutoff valve. Screw the feed adapter onto the valve. Reconnect the supply line to the adapter. Attach your RO tubing to the adapter’s 1/4 inch port. This is cleaner and more professional.

Turn the water back on slowly. Check for leaks. Tighten if needed.

Any good reverse osmosis system installation guide will tell you — leak check everything twice.

Step 5: Install the Drain Saddle

Your RO system needs a place to send waste water. That’s the drain saddle. It clamps onto your sink drain pipe.

Find the vertical or horizontal drain pipe under your sink. Clean the spot where you’ll attach the saddle. Clamp the drain saddle onto the pipe. Drill a 1/4 inch hole through the pipe using the saddle as a guide. Don’t drill all the way through both sides — just one side. Attach the tubing from your RO system’s waste water port.

This step creates a permanent connection. Make sure the hole is above the P-trap so sewer gases don’t come back up.

Some people skip the drain saddle and run waste water into a floor drain or utility sink. That works too if you have one nearby.

Step 6: Connect All the Tubing

Now the puzzle comes together. Run tubing between each component: Cold water feed to the first filter. Between filter housings. From the last filter to the RO membrane housing. From the membrane to the storage tank. From the storage tank to the dedicated faucet. From the membrane to the drain saddle for waste water.

Cut tubing to length with a utility knife. Cut straight, not angled. Push tubing firmly into each fitting until it stops. Pull back gently to make sure it’s locked. Use colored tubing if provided — blue for clean water, red for waste, etc.

Don’t kink the tubing. Kinks block water flow. Leave some slack for future filter changes.

Organization matters in any reverse osmosis system installation guide. Neat tubing runs look better and work better.

Step 7: Install Filters and Membrane

Don’t forget this step. Many people install everything and realize they never put the filters in.

Remove the filter housings using the included wrench. Insert the sediment filter in the first housing. Insert the carbon filters in the next housings. The RO membrane goes in its own special housing — usually a horizontal cylinder. Push it in firmly until it seats. Replace all housings and hand tighten. Use the wrench for final snugging — not too tight.

Check the manual for exact order. Different systems have different filter sequences.

Step 8: Turn It On and Flush

Open the storage tank valve. Open the dedicated RO faucet. Turn on the cold water supply. Watch for leaks everywhere. Leave the faucet open for 1 to 2 hours. This flushes out air and carbon fines from new filters.

After flushing, close the faucet. Let the tank fill completely. This takes 2 to 4 hours. Once full, open the faucet again. Let it run for another 10 to 15 minutes. The first few tanks of water may have a slight carbon taste. That’s normal. It goes away.

Test your water with a TDS meter. It should read under 50 ppm. Ideally under 20 ppm.

Congratulations. You’ve completed this reverse osmosis system installation guide. Your RO system is now ready for daily use.

The Bottom Line

Installing a reverse osmosis system takes half a day and basic tools. The steps are straightforward — faucet first, mount the system, connect water supply, install drain, run tubing, add filters, flush everything.

Follow this reverse osmosis system installation guide and you’ll save the $150 to $300 you’d pay a plumber. Plus you’ll know your system inside and out for future maintenance.

Take your time. Check for leaks. Flush thoroughly. Then enjoy the best tasting water you’ve ever had from your own faucet.