Installing a Reverse Osmosis System under the Sink

Water quality issues are a concern for many homeowners, especially those who get their water from a well. Since their introduction in the 1970s, reverse osmosis systems have become a widely-used option in many homes since they offer a simple but effective way to obtain safe drinking water on demand that is superior to other common options like bottled water or pitcher filters. The two main options for reverse osmosis in your home are whole-house (which typically requires professional installation) or under-sink (which can be installed by a homeowner with some DIY skills and basic tools). Typically, an under-sink reverse osmosis system can be purchased for between $150 and $300. If you do the installation yourself, there’s no additional out-of-pocket charges for installation aside from routine maintenance over the life of the unit (e.g. filter changes).

installing a reverse osmosis systemThe process does vary somewhat depending on the manufacturer of the system you’ve purchased for your home, but installing an under-sink reverse osmosis system is normally fairly straightforward – install the reverse osmosis unit and its storage tank under the sink, install the reverse osmosis unit’s faucet and hook up the appropriate pipes and water lines.

Tools Needed:

  • -Drill
  • -Philips head screwdriver
  • -Razor blade
  • -Adjustable wrench or pliers

*Note: These may vary depending on the manufacturer’s instructions but most units can be installed with the basic tools at your disposal. Bear in mind that any drilling needed should be done with the appropriate bits for the material (wood, ceramic tile, etc.)


Step 1

Make room under the sink where the reverse osmosis unit and water tank will be located. Some units offer the ability to mount them either vertically or horizontally, which may make it easier to install depending on the space you have available

Step 2

Before you go any further – make sure the main water line to your house is turned off.

Step 3

Identify the sink’s cold water line. This is where you will connect the reverse osmosis system in order to supply it with water to be filtered.

Step 4

Cut into the cold water line and attach the water line splitter. This will allow the cold water line to feed both the regular sink faucet and the reverse osmosis system

Step 5

Attach the drain pipes for the reverse osmosis system to the main sink drain. This will allow the reverse osmosis system to dispose of waste water containing sediments and other particles it filters out of your water as well as allowing the sink drain to be used normally.

Step 6

Install the faucet on your sink. This will more than likely require that you make a new hole in the counter or sink depending on placement of the faucet. While you can readily drill through a wooden countertop or punch a hole through a stainless-steel sink to accommodate the faucet, cast-iron or porcelain will likely require specialty tools in order to do it properly. Once the faucet is installed, you’ll need to hook it up to the reverse osmosis unit.

Step 7

Verify that everything is connected – the reverse osmosis unit, the storage tank, faucet and drain pipe.

Step 8

Turn your water back on and run the reverse osmosis unit. Most systems require that you run a few cycles of water through them to flush them out first, plus you should also take this time to check for any leaks in the system. If all goes well, you can start enjoying your pure water right away!

Justin Krutz combines his interests in home improvement and writing to share knowledge about a variety of topics including reverse osmosis installation.


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