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How to install a Sink

by Lorenz Prem
published on February 21 2011 6:39 pm

One of the joys of doing things yourself is testing your limits. With every project completed your skills grow. What used to be out of reach becomes possible. Installing a kitchen sink is one of these milestones. It does not require plumbing skills, but seems daunting enough most people never try. Let's take a look at what's involved.

Installing the hot and cold water valves

The project begins at the plumbing stubs below the sink location. There will be hot and cold water lines and a sewer connection. The hot and cold water lines are either capped (as they are in the picture), or have valves installed. If the lines are capped, the valves need to be added.

Plumbing valves are sold at the home center in dizzying variety. If you look closely, you'll notice that only a few properties change between one valve and the next. Let's examine them one by one:

  • Compression fitting vs. pipe thread: What's at the end of the water pipes determines what type of valve you need. If the pipe is capped or just ends, you'll need a compression valve. This type can be installed directly on a pipe without any plumbing threads. If your pipes end in either male or female pipe threads, the valve has to have the matching threads. Buy either a female or male NTP (national pipe thread, the standard for threads on water pipes) valve.
  • Straight vs. angle: The path the water tales in the valve is either straight (in a straight through valve) or a 90 angle (in a corner valve). The 90 degree bend saves space below sink. The water lines connect to the top of the valve instead of the front. In most cases 90 degree valves are the way to go. The valves used in the pictures are 90 degree valves.
  • Quarter turn vs. full turn: Valves vary by how far the handle must be turned to turn the flow of water completely off. The most common variety are 1/4 valves and full turn valves. The choice between the two comes down to personal preference.
  • Inlet and outlet diameter: the inlet diameter of valve needs to match the pipe in your home. The outlet diameter should match the inlet diameter of the faucet at your sink. That way you can use flex hose with the same size fittings on both ends to connect the valve to the faucet in the next step.

My go- to valve is a 90 degree full turn valve with a 1/2" inlet (pipe diameter in most homes) and a 1/4" outlet (the inlet diameter of most faucets). Measure your pipe and faucet inlet diameter carefully. Otherwise you might need another trip to the store.

Installation of all valve types begins with cleaning the pipe. As a rule a tight joint is only possible on a clean surface. Compression fittings are installed by placing the compression ring on the pipe and securing the valve around it using a pair of pliers. Valves with pipe threads are screwed into place. Apply Teflon tape to the male part of the joint and screw the valve into place with two wrenches. One wrench to hold the pipe in place, the other to spin the valve.

Installing the hot and cold water lines

Once the valves are in place, it is time to install the water lines. For both hot and cold a flex hose must be connected to the valve stem and the faucet's corresponding inlet. Flex hoses come in different diameter. Most will have female threads at both ends. If you have matched the valve diameter to the faucet's inlet diameter, picking the right part is just the matter of finding a hose of the correct length and the correct diameter. If the there is a mismatch, you will need to find the correct adapter to make the connection.

Steel hoses are more durable than plastic hoses and the preferred choice. Installation is very similar to valve installation. Place Teflon tape on the male ends, which are on the valve stem and the faucet inlet. Connect the hose and tighten the connection with two wrenches. Take care not to spin the valve or twist the flex hose. Too much torque on the valve or a twisted flex hose can cause leaks down the road.

At this point your hot and cold water connects are functional. Now that we can fill the sink with water, we must connect the drain.

Installing the drain pipes

Drain pipes are the fun part of this project. Under sink drain joints are made with compression fitting. These fittings can be secured and loosened at will. This makes it easy to assemble the system by trial and error.

There are three parts to the drain pipes: a vertical stem that connects to the underside of the sink, the p-trap for trapping solids, and a return that connects the p-trap to the sewer connection in the wall. The sewer connection in the wall will most likely be a compression fitting as well, which makes installation easy. If a pipe thread is used or the diameter does not match the diameter of the sink, purchase an adapter or reducer.

Residential drain pipes come in two diameters: 1 1/4" and 1 1/2". Bathrooms often use the smaller drain pipes, kitchen sinks the larger pipes. Measure before you purchase any parts.

Install the parts by tightening the compression nut on each piece. Teflon tape is not needed, but it will plug leaks should the compression joint need help. Some pipes must be cut to length to match your location. A hacksaw is ideal for this job. Adapters and reducer often need to be glued into place with PVC glue. The glue is sold in the plumbing department along with the pipes and fittings. Read the label on the glue bottle at the store and make sure you understand how to apply the glue. In some cases you will need to use a separate activator along with glue.


Installing a sink takes little more than tightening a few fittings. You will spend the most time in your car on your way to the home center and back. This is one of the jobs where bad planning can cause may trips back to the home center. But it's also a job that creates a lot of satisfaction.

About the Author
"Lorenz is the founder of Hingmy. When he is not reviewing power tools or improving the site, he is building things in his workshop or playing hockey."