How to Add a Second Bathroom Sink Connecting to Single Pipes

A second bathroom sink can resolve timing issues as you and your spouse get ready for work or bed.
Bathroom sinks receive water from hot and cold supply lines.Bathroom sinks receive water from hot and cold supply lines.
If connected by a countertop and vanity, the setup gives you additional room to operate and store your items, from curling irons to toothbrushes. Two pedestal sinks can give your large master bath a touch of modern flair. To upgrade a single-sink bathroom, you will need to brush up on your plumbing skills to connect the water pipes. You also may need to cut into the wall or floor if you go the pedestal route.

Step 1

Shut off the water at the main valve. Drain water from the lines by turning on two or three faucets, including the sink in the bathroom where you will be working.

Step 2

Access the hot and cold water supply lines and drain pipe as they enter your bathroom. If the dual sinks will be contained within the same vanity, you can simply work within the cabinet. To install a second pedestal sink, you will need to remove the sink and cut the wall or floor to create a path for the pipes to reach the second pedestal.

Step 3

Cut both the hot and cold water pipes behind the original sink's shutoff valves. Leave at least a 3/4-inch stub of pipe before the shutoff valve to give you room to attach a coupling later. Copper plumbing will require a tube cutter you rotate around the pipe; plastic pipes can be cut with a hacksaw and cleaned of burrs with a utility knife.

Step 4

Cut the drain pipe. Plug the pipe with a rag to prevent sewage odors from escaping.

Step 5

Attach tee fittings to the cut supply lines. Home improvement warehouses carry a number of directional tee shapes in various pipe sizes to satisfy your needs. Use solder or compression fittings to attach copper fittings; apply primer and cement to connect plastic parts.

Step 6

Cut pieces of pipe long enough to reach the second sink to be installed. Attach these supply lines to the opening in the tees that will serve the second sink.

Step 7

Cut two short pieces of pipe to connect the supply lines to the original shutoff valves. Attach the pieces of pipe to reinstall service to the original sink.

Step 8

Install elbows to create the stubs on the supply lines for the second sink. Attach shutoff valves and flexible tubing for both the hot and cold controls, completing installation of the second sink.

Step 9

Install a tee on the drain pipe. Cut pipe to reach the locations of each trap under the sinks. Connect the traps to the drain.

Step 10

Turn on the main valve slowly. Check your installation thoroughly for any leaks and repair as necessary.

Step 11

Reinstall any cut wall board or flooring, and create a smooth finish.

Things You Will Need

  • Copper tubing cutter or hacksaw
  • Utility knife
  • Tee fittings
  • Solder or wrenches (copper pipes)
  • Primer and cement (plastic pipe)
  • Elbow fittings
  • 2 shutoff valves
  • 2 flexible water supply tubes
  • Drain pipe, fittings and trap


  • Be sure to stay consistent in the type of pipe used, as CPVC fittings will not fit ABS or PVC plastic pipes. You can buy transitions from copper to plastic if you are not comfortable sweating fittings or using compression pieces.


  • Cement for plastic fittings has a strong odor and can cause respiratory discomfort. Use it only when working in a well-ventilated area.
  • Sweating copper fittings requires use of a torch. Exercise extreme caution when working in tight spaces or around woodworking or beams.

About the Author

Trevor Wendzonka is a public relations specialist based in the Midwest. He worked for a 30,000 circulation newspaper for 15 years as a sports and government writer, and spent a number of years editing and designing pages on the copy desk.