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How to Install a Bathroom Sink

Pro Referral > Home Guides > Bathroom > How to Install a Bathroom Sink
How to Install a Bathroom Sink

Bathroom designers’ ears perk up when we begin talking about bathroom sinks. Why? The bathroom sink provides a ton of design possibility. From pedestal to vessel, from integral to wall-mount or console, there are certainly a lot of options.

 

In many ways, the type of sink selected will be dictated by design decisions, many driven by budget or space–including the need for storage. Deck-mounted sinks, those that sit in a cabinet (aka a vanity) are set into a cut-out in the paired countertop. These sinks (or lavatories) can either “drop-in” from above or be attached from below (i.e. undermount).

 

For the purposes of this article we will cover the installation of a deck-mounted, “self-rimming” sink. These sinks are available in a multitude of colors, shapes, and sizes. Materials range from fiberglass or acrylic to enameled steel and vitreous china to more exotic options like copper or glass. They are by far the most commonly selected, based in part on cost and ease of installation.

 
Tools Materials Skill Level Estimated Time
• Channel locks • Sink (with template) Intermediate 1 to 3 Hours
• Pipe wrench • Faucet (salvaged or new)
• Adjustable wrench (7-8”) • Pop-up drain assembly (salvaged or new)
• Caulk gun • Plumber’s putty
• Flashlight • Teflon tape (optional)
• Drill driver (with 1/2" drill bit) • Clear silicone caulk
• Jig saw and router or belt sander • 1 1/4" P-trap with J-bend
• Pencil • Tailpipe
• Scissors or utility knife • 2x Faucet supply lines (3/8 in. OD x 1/2 in. IPS – salvaged or new)
• Painter’s tape

Prepare to Install: Plan Your Purchase

Like most work in a bathroom, the installation of a new sink is likely timed with other work. Installing a new sink is an opportune time, at minimum, to also upgrade a faucet.

 

Sink bowls will come pre-drilled with one or three holes. While the single-hole option is pretty self-explanatory (i.e. will only accept a single-handle faucet), it’s worthwhile to acquaint yourself with the spacing found on sinks with three holes.

 

For three-hole bathroom sinks, holes are set at one of two possible spans or spreads. Based on the distance measured from the center point of the outside holes, you'll find sinks with either eight-inch center set or four-inch center set drillings. Eight-inch spacing is designed for "wide-spread" faucets (hot and cold independent of the spout); four-inch spacing is designed (primarily) for "centerset" faucets (hot and cold integrated with the spout).

 

    1. Selecting Your New Sink

    When selecting your new sink you must coordinate with the faucet you either already have or one that you plan to select, purchase, and install.

     

    While many vanity cabinets sold these days have a preconfigured top and sink, some may still be purchased independent of a top and a sink. Ensure that the cabinet you select will physically fit into its designed location, and that it is both wide and deep enough to accept the sink you plan to install. It’s important to note that cabinets designed for the bath are typically shallower than, say, kitchen cabinets, and will range usually from about 19” to 22” deep.

     

    Prepare for the Install: Final Checks

    Regardless of whether you selected to install a new vanity cabinet in conjunction with your new sink, this cabinet should be set in place and mounted appropriately to the wall.

     

    Note: If your sink is being installed in the context of a full bath remodel, it is also an opportune time to consider the re-positioning of fixtures and to upgrade, or at least inspect, your existing rough plumbing. Needless to say, a pro plumber can help in this regard. Everything in the rough work phase should be complete prior to installing your vanity cabinet and further, your sink.


    2. Preparing the Countertop

    One advantage of self-rimming bathroom sinks is that they can be installed in virtually any counter surface (i.e. in any material). The only requirement here is that the recess in the top will need to be cut prior to installing the sink. Most sinks are packaged with a paper template that is scaled to the actual size of the sink. If possible, deliver this template, or at minimum the dimensions of your selected sink, to your countertop fabricator or installer. As hinted at above, bowl (and lip) shapes and sizes, depths and heights, and many other aspects of a sink can vary greatly.

     

    If you are not replacing your vanity top, shop carefully paying particular attention to your cut-out requirement and the selected sink's lip. To come up with the sink's lip projection, you may need to calculate by subtracting cut-out width from overall or "basin" width. Your new sink will need to slide comfortably through the top's opening, but will need to cover it when eventually sitting flush to the deck.

     

    To Cut a New Sink Opening:

     
    1. 1) Center the provided template and thoroughly fit it to the deck.
    2. 2) Follow guidelines and cut out the portion of the template that represents the basin.
    3. 3) Trace around the inside edge of the opening in the template.
    4. 4) Drill at minimum one starter hole using a 1/2" drill bit.
    5. 5) Insert your saw blade into your starter hole and follow the template. Cut on the inside edge of your traced line using a jigsaw fitted with a blade appropriate for the material you are cutting into.
    6. 6) Clean up the opening with a belt sander, router, or equivalent.

    Prepping & Mounting the Sink

    3. Install Your Faucet

    Logic has it that if you are replacing a bathroom sink you'll either have a faucet you have not yet installed or a faucet uninstalled from your previously installed sink. Install your faucet prior to setting your sink into your vanity cabinet.

     

    You will have opened your sink’s packaging as part of discovering and utilizing the sink's associated template. Completely unpack your new sink while thinking about using any available cardboard to create a safe working surface. Mount your faucet to the sink following manufacturer requirements. Connect plumbing supply lines to the faucet at this time.


    4. Install the Sink Drain

    If installing a new faucet, it will be packaged with a coordinating pop-up drain. If you are re-installing your existing faucet, but didn't retain the existing drain, pop-up drain assemblies are available and sold independently.

     

    The drain will likely come as two parts threaded together at the drain's rim or flange.

     
    1. 1) Disassemble it.
    2. 2) If the pop-up arm is also pre-assembled: unscrew the pivot seating nut at the stopper rod, remove the rod, and remove the drain stopper.
    3. 3) Set the full assembly aside.
    4. 4) Line the sink's drain opening with a rope of plumber’s putty and press it firmly into place.
    5. 5) Place the drain flange in place and, pulling the sink up at an angle, slide the threaded portion of the drain up through the sink's drain hole.
    6. 6) Include any supplied gasket, and screw the drain together, by hand only.   Note: When screwing down the drain, remember that the opening for the pop-up rod arm should be oriented toward the rear of the sink.
    7. 7) Holding the drain firmly in place, give the drain’s nut one final ¼ turn with a pipe wrench or appropriate sized channel locks.
    8. 8) Remove any excess plumber’s putty that sneaks out inside the sink bowl.

    5. Install the Faucet's Pop-Up

    1. 1) Install the drain stopper, inserting the pop-up rod.
    2. 2) Loosely screw down the rod’s seating nut.
    3. 3) Swing the pivoting rod upward so that the sink stopper closes.
    4. 4) Insert the lift rod into the faucet, allowing it to pass downward through the set screw opening in the lift rod scrap.
    5. 5) Use the provided linkage to make the connection between the pivoting rod and the lift rod.
    6. 6) Tighten down the seating nut, but do not over tighten.

    6. Set the Sink

    Set the prepped sink into the recess of your counter. You may choose to pre-assemble some of the under-sink plumbing prior to doing this. It may make drain connections a little easier later. Line your sink drain up with the under-sink plumbing as you set the sink.


    Making Plumbing Connections

    7. Making Drain Connections

    With modern plumbing codes, your sink's rough drain should be entering at the back of your vanity cabinet. Purchase an appropriate 1 1/4" P-trap in a material of your choosing. Ensure that the trap arm will reach to the rear wall.

     

    The trick with installing your P-trap is remembering its purpose. P-traps are designed to hold water, and in turn prevent sewer gases from entering the home via the drain. To accomplish this, the P-trap is installed below the plane of the drain outlet. Drain outlet stubs are typically found between 14" and 18" off the finished floor.

     

    If your pop-up drain is not long enough to reach the P-trap’s J-bend, you’ll need to purchase and add an additional tailpipe extension. The tailpipe in essence extends the sink drain downward.

     

    Your P-trap as well as your tailpipe will be held together with slip nuts. Don't forget to include any packaged gaskets when installing. Be conscious not to cross-thread these fittings, and make them snug by hand only. Remember, righty tighty lefty loosy. You can tighten these nuts down further if you find that hand-tightening alone does not do the trick.

     

    Note: If required, you may "swing" your P-trap roughly two inches to the left or the right to catch or align with a drain outlet. You may need to purchase additional bends and fittings if your vanity cabinet does not center on your drain outlet.


    8. Making Supply Connections

    You should have pre-installed supply lines. It is recommended that you use braided, flexible supply lines for ease of installation. Faucet supply tubes should be fairly universal, but select an appropriate length and fitting. In an ideal world, you'll be looking for hoses with 3/8” compression fittings. Line these up with shut-offs on the in-cabinet supply stubs and tighten by hand. Give them a 1/4 turn with a non-marring wrench to complete the connections on both hot and cold water lines.


    9. Checking Your Plumbing Connections

    At this point, inspect your work. Ask yourself: Is the sink aligned and completed as I want it to be? Close the sink stopper and run the water until the basin is full: Are there leaks on the supply side? Drain the sink and inspect underneath using a flashlight: Are there leaks on the drain side?

     

    Tighten connections with an appropriate wrench to eliminate any under-sink leaks.


    Finishing the Installation

    10. Seal Around the Sink

    Unlike kitchen sinks, most self-rimming bathroom sinks will not include mounting clips. If yours does, install the mounting clips. Otherwise plan to seal your sink to your counter surface using 100 percent clear silicon caulk. Apply a thin bead and smooth with a gloved finger.

     

    Tip: Handheld tubes of caulk can help with getting behind the sink. This is an absolutely essential step in a sink installation as this is a location where water will frequently splash up, possibly damaging your cabinet if not sealed correctly. Allow the caulk to cure overnight before use.


    Level of Difficulty

    Installing a bathroom sink is a relatively easy proposition, especially if the countertop cut-out is already present. Add an hour to estimated time for cutting the opening in a wood or laminate countertop. Creating recesses in other materials may require more advanced techniques and may take longer.

     

    Installing a sink requires working with household water. If you have questions or concerns about your plumbing or your plumbing skill, seek the advice of a licensed plumber. Good Luck.

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