If you bought a reverse osmosis filter, congratulations. You’re one step closer to cleaner drinking water. But are you ready to install the system? It’s not complicated, but it can be a challenging DIY project if you don’t have plumbing experience. So, let’s review the reverse osmosis installation process. These tips will help get you to the finish line.
How Do Reverse Osmosis Systems Work?
Reverse osmosis systems force water through a series of filters that remove specific contaminants from chlorine to heavy metals. Purified water is collected in a storage tank while waste is flushed down your drain line.
There are five primary components in most multistage systems:
The semi-permeable RO membrane is vulnerable to sediment, chlorine and other chemicals that can damage its delicate structure. Pre-filters remove those contaminants, improving your water quality and the service life of your reverse osmosis system.
The RO membrane is a semi-permeable film that excludes all contaminates larger than its microscopic pores. Reverse osmosis removes 99-percent or more of dissolved solids plus heavy metals like lead and fluoride.
Post-filters remove trace contaminants that the previous filtration stages missed. Some also have alkalizing filters that restore beneficial minerals stripped from water by the RO membrane. Not all RO systems have post-filters.
The reverse osmosis process is slow, so an RO system can’t produce water on demand. Instead, water is held in a storage tank and replenished as it’s used, guaranteeing a steady water supply. Tanks hold 3-5 gallons depending on the size. The storage tank is the largest and most complex part of a reverse osmosis system.
Reverse osmosis filters come with a special drinking water faucet for three reasons:
An RO system doesn’t produce enough water for washing dishes. Once it’s installed, you’ll get filtered water for drinking and cooking from the RO faucet and unfiltered water from the regular faucet for other household uses.
Hot water damages RO membranes. A reverse osmosis system is hooked up only to your cold water line to prevent accidental exposure.
Most RO systems also use a special air-gap faucet that prevents the backflow of contaminated water into the storage tank. It’s a valuable safety feature.
Where Is an RO System Installed?
Whole-house RO filters are rare — most are installed under the kitchen sink. But you can hook it up in any desired location, such as a garage or utility room, but if you want it to feed your kitchen sink, the installation could get tricky.
If the filter isn’t near your sink location, you may need a delivery pump. Unless the cabinet under your sink won’t work because a garbage disposal is in the way, it’s the most convenient place for a reverse osmosis system.
Planning the Installation
Before you gather your tools, unpack your system and verify that it contains all the promised parts. Read the instruction manual from start to finish. If you need extra tubing, adapters, or fittings to fit irregular plumbing, make a list and head to the hardware store. You’ll also need Teflon tape and a tube of clear caulk.
The space under the sink is tight, so you’ll need to plan the installation, starting with test fitting the components. You’ll want to position the filtration unit and storage tank where you want them to be. Vertical or horizontal installation is an option with some models — check the owner’s manual.
The mounting surface should be level and protected from freezing temperatures. If you’ve ever had a frozen pipe under your sink despite your home being heated, now’s the time to add an extra layer of insulation.
We also recommend having the sink prepared for installation before beginning the project. Most have a predrilled hole that can be used for the faucet. If it doesn’t, you’ll need to drill one.
Step-By-Step: How to Install a Reverse Osmosis System
Now the stage is set, so it’s time for the show. Remember, however, that all reverse osmosis systems are different, so these are general guidelines. Always refer to your owner’s manual.
Before you begin, assemble the tools and supplies you’ll need to make it a smooth process:
- Plumber’s tape
- Adjustable wrench
- Screwdriver or a drill and bit to match the included fasteners
- Sponge or towel for mopping up drips
Now, turn off the cold water valve, and let’s get started.
#1 Faucet Installation
Installing the faucet first allows you to feed the attached tubing down the faucet hole before it gets too crowded under the sink. Trust us, you’ll need the space.
Feed it down through the opening, and then mount the faucet body to the kitchen sink, seating the faucet base into a layer of clear caulk to prevent leaks. Make sure the spout swivels freely. Reach underneath and attach the included washer and nut to the faucet stem to keep the assembly secure.
#2 Installing the Drain Saddle
Nest, install the drain line adapter, or drain saddle, onto the drain line — your system may include a rubber gasket. Place it as far away as possible from the dishwasher and garbage disposal outlets to prevent clogging. Secure the drain clamp to the drain pipe, being careful not to overtighten.
#3 Position the Tank
Tape the threads of the tank valve, and then hand-tighten the faucet connector onto the tank— don’t overdo it. Next, slide the tank into position under the sink, preferably below the faucet.
#4 Mount the Filter Assembly
Unless you have the rare freestanding unit, rough fit the filter housing to the cabinet wall, marking the locations for the fasteners. Use a level to ensure it’s straight, leaving at least 16 inches of space between the bottom of the bracket and the floor for maintenance. Screw the fasteners on the wall and then hang the filter.
#5 Connect the Water Lines
Most reverse osmosis system manufacturers use quick connect fittings and color-coded tubing to make the tubing connection process easier:
Connect the yellow line to the cold water line using the feed valve/adapter that came with your reverse osmosis filter system or an alternate adapter that you purchased separately.
#6 Connect the green line to the storage tank valve/tank connector and the outlet port of the filter system.
Connect the black line to the drain saddle valve and the flow restrictor. If the plastic tubing is too long, cut it to avoid loops. This helps maintain the storage tank pressure.
Connect the blue line to the faucet connector on the storage tank.
Avoid tightening the connectors/nuts more than a half-turn past hand tight.
#7 Install the Filter Cartridges
Finally, install the filter cartridges, making sure they’re secure. Next, we’ll pressure test the system.
#8 Perform a Pressure Test
Close the storage tank valve, turn the cold water on and purge any air from the cold water line by opening the RO faucet. You’ll hear hissing or gurgling as air exits the system— it’s normal. In the meantime, check the system from the sink faucet to the feed water valve for leaks.
In about 15 minutes, water will begin trickling from the faucet as it works its way through the filter. It may be discolored at first as carbon dust is rinsed from the prefilters. When the water runs clear, close the faucet, open the storage tank valve and allow the tank to fill. This takes 2-12 hours depending on your incoming water pressure.
When the tank is full, open the faucet and drain the contents, effectively flushing the whole unit. Allow the tank to refill, checking one last time for leaks and you’re now ready to drink from your reverse osmosis system.
Reverse Osmosis System Installation —When to Call a Professional
A quality reverse osmosis system costs as little as a few hundred dollars, so it’s a shame to blow the savings on professional installation. But while most homeowners can install a reverse osmosis water filter in a morning, these circumstances may call for a pro:
While most faucets come with predrilled holes for the faucet, some don’t. Drilling a hole in a stainless steel sink isn’t difficult, but stone countertops require special handling. It takes skill to cut marble or granite without cracking it. If you’re not experienced cutting stone, it’s better to be safe and call an expert than risk damaging a multi-thousand-dollar countertop.
Installing a reverse osmosis system in an area far from your kitchen sink or a drain line requires extra parts and expertise. Similarly, if you want to hook your system up to a refrigerator, it’s helpful to have a plumber’s advice.
And if space under your counter is tight, it may be worth paying an expert to fit it just right. You’ll have your reverse osmosis system for a decade or more, so it pays to be satisfied with the installation.
Installing a water filter when you have better things to do is never fun but keep your eye on the prize. The moment clean tap water flows from your reverse osmosis system, the hassle of installation will be forgiven and forgotten.