How To Plumb a Pedestal Sink

How To Plumb a Pedestal Sink

A pedestal sink can make a bathroom look more open and stylish. No matter your reason for installing a pedestal sink, we’ve got you covered.

Before purchasing or obtaining a sink, you’ll want to remove your old sink. The reason for doing this is that you’ll want to choose a sink that fits with the existing waste, vent and water rough-in. If you get a sink, and it doesn’t end up fitting, you’ll have to alter the rough-in or you’ll have to return it. We’d like to help you avoid that extra hassle. Pedestal sink plumbing is simple and shouldn’t take you more than a day or so to complete.

Removing the Old Sink

You’ll likely need a few tools before you get started:tools laid out

  • Safety Glasses
  • Adjustable Pliers (Channel Locks) Monkey Wrench
  • Utility Knife
  • Rubber Mallet
  • Hammer and Chisel
  • Drill and Drill Bits
  • Bucket

Once you’ve rounded up these tools, it’s time to remove the old sink.

Begin by turning off the sink’s water supply. Turn a faucet to relieve water pressure in the sink’s pipes. Place your bucket underneath the P-Trap — the P-shaped tube directly under the sink’s bowl — and loosen the slip nut at the top of the trap. Remove the trap, making sure to empty any water into your bucket as you take it out.

Relocate your bucket to be directly beneath the water lines. Disconnect each one with your adjustable wrench, catching any water that spills out in your bucket.

Your existing vanity top will probably have some sealant along the top and sides, it may be silicone caulk or some type of mastic. Go ahead and cut the sealant with your utility knife.

If you are planning on keeping your existing sink, you can loosen the vanity top from the sink using a rubber mallet. This will usually loosen the top without cracking the surface. If someone was using a mastic glue too liberally you may have to use a thin chisel or a putty knife to gradually break the seal.  Once it is sufficiently loose, carefully remove it. You should probably obtain help when removing this piece, as vanity tops are usually quite heavy.

You should now be able to see inside your old sink base from the top. Usually, there are screws to remove before you can extract the base from the bathroom.

You can reinstall your P-Trap at this point, as you’ll need it in place when picking out a sink.

Pedestal Sink Installation

Measure the distance from finished wall to the center of the p-trap, from the floor to center of the waste opening and from the floor to the center of the water supplies coming out of the wall. You’ll also want to be sure the sink will fit in your bathroom in general. You have no idea how many times we’ve gone into a customer’s home to install an owner supplied pedestal sink only to find that the bathroom door won’t open or close because the sink it too long or wide. Also worth noting, check the height on the fixture if you have an existing mirror in place.

You’ll need a few more tools for installing than those used for the removal of the old sink:

  • Power Drill
  • Stud Finder, or Equivalent
  • Silicone Sealant
  • Plumber’s Tape (recommended)

Lining Everything Up

Once you’ve picked out your sink and faucet, you can begin by placing them in your bathroom. You won’t be doing any installation just yet, just lining things up and doing a bit of eyeballing.

turned on black shower head sprinkling drops of water upwardsPlace the base in the bathroom, move it into place against the wall. You’ll want the P-Trap to be inside the base’s cutout, and the base to be in between the water supply shutoffs. Again, you’re just making sure everything fits at this point — you aren’t installing anything permanently just yet.

Once the pedestal is in place, place the sink on top and verify that it fits snugly. Often there is a “lip” on the bottom of the sink that should be completely covered up by the pedestal. Adjust the sink and pedestal until this is the case.

Now, you’ll want to adjust the pedestal and sink until the sink sits flush against the wall.

Mark the positions of your sink’s holes on the wall. Use a stud finder to locate the studs behind the wall. Although the sink will get some support from the pedestal base, I like to have wood backing to anchor the sink. Drywall anchors don’t cut it. Remove the sink from the pedestal and set it aside. You’ll want to drill ⅛” holes into the wall at these locations with a power drill.

Installing the Faucet

Take the sink aside and grab all your faucet’s parts. All faucets will have slightly different instructions, so consult your manual first.

First, take your faucet’s cover plate if the faucet has a cover plate (Make sure you look to see if you pedestal sink is manufactured for a 4” center or an 8” center faucet — place the cover plate over the holes in your sink where the faucet will go. Insert the faucet’s water supply lines (they’ll be connected to the faucet itself) through this plate, and also through the holes in the sink.

You’ll now install a metal washer on the underside of the sink. Slide the washer over the stud next to the faucet’s supply lines. Slide the supplied nut onto this, and tighten it so that the faucet is fastened in place. Be sure the faucet is lined up before tightening this nut completely.

Installing the Sink Drain

If your drain came already assembled, you’ll want to disassemble it now. Remember how you take it apart so that you can put it back together soon.

Begin by applying a generous amount of silicone sealant to the underside of the flange — the ring-shaped piece that sits in the hole at the bottom of the sink. Sometimes the flange will be attached to a tailpiece, and sometimes you’ll have to screw on the tailpiece after inserting the flange. Only apply silicone to the bottom of the portion that will rest on the sink’s drainage hole.

From the underside of the sink, place the rubber gasket over the flange. Then add the washer. Then add the nut. Tighten everything hand-tight for now. You just want to keep everything in place as you add the rest of the parts. If your flange came with a plastic washer, install that into the bottom of the flange assembly now.

sink drain


Now you’ll install the tail piece. Apply some plumber’s tape (if you have it) to the threads of the tail piece, and screw it onto the flange with your hand. If the drainage assembly uses a slip joint plumbers tape is not necessary. The pivot piece sticking off the tail piece should point towards the back of the sink. To accomplish this, tighten the tail piece all the way, and then loosen the flange nut and rotate the tail piece. Once it is facing the rear, tighten this nut with a pair of pliers or a wrench to secure it in place.

You may wipe off excess sealant on the inside of the sink bowl at this point.

Follow your pop-up drain’s instruction manual for instructions specific to your drain assembly. In general, you’ll be installing the drain plug and lift rod, so that you can plug and unplug your sink. Ensure this part of your sink works before installing your sink top.

Installing Your Sink on the Pedestal

The time has come to place your assembled sink onto the pedestal base.

Once you’ve placed the sink on top of the base, look at the drain assembly. You want the drain assembly to enter into the P-Trap about an inch or an inch and a half. If the drain assembly does not enter this far, you’ll need to add an extension piece to it.

Installing an Extension Tube (If Required)

To add an extension tube first unscrew the nut on the top of the tube. Slide the nut and the included washer onto the existing drain tube. Slide the extension tube onto the drain assembly as high up as you can. Hand tighten the nut for now since we’ll need to adjust the tube once we place the sink back on the base.

Place the sink back on the pedestal. Make a mark on the extension tube about an inch or so into the P-Trap. Remove the sink from the pedestal once again, and cut the extension tube at the mark you made. You can use a tube cutter, or any other tool you have that can cut through the tubing. Sand the end of the tube to get rid of any rough edges.

Connecting The Sink to the P-Trap

Remove the nut and washer from the end of the P-Trap and slide them onto the drain assembly. Leave about two inches from the nut to the bottom of the drain assembly. Make sure to have the threads facing downwards so that you can screw the nut back onto the P-Trap once the sink is in place.

Place the sink on top of the base, making sure the drain assembly falls into the P-Trap. At this point, you should slide the nut and washer we placed on the drain assembly down onto the P-Trap. Fasten it securely.pedestal sink

At this point, you should have your drain assembly connected to the P-Trap, and the P-Trap connected to the pipe extending out from your wall.

Grab the sink and pedestal firmly, and push the sink flush against the wall. Nudge the whole thing until the holes in the wall line up with the holes in the sink. Insert the screws, and any washers that came with them, and go ahead and attach your sink to the wall now.

Install the Supply Lines

Take each of the dangling supply lines and insert them into the appropriate supply line shutoff valves. Tighten each one by hand first, and then use a wrench to tighten them a tad more.

If your water supply lines have too much length, loop them into a circle or two before inserting them into the water shutoffs. You can also choose to cut the supply lines, but this is more difficult and will not be covered here.

Turn the hot and cold water shutoffs on once you’ve securely fastened the supply lines. Do not attempt to run water through the faucet yet.

Final Steps

Check that your sink is firmly connected to the wall by tugging at it gently. Do not be too forceful here, but apply enough force to verify the screws are in securely enough. If it feels a bit loose, tighten the screws a bit.

Clear Any Debris

Before turning on your sink, you’ll want to remove the aerator from the faucet. The aerator is responsible for making sure the stream of water coming out of the faucet is smooth and consistent. If there is any debris in the faucet or piping, we’ll want the aerator removed when we first run water through it. This flushes out any debris, so it does not get stuck inside the faucet.

Remove the faucet’s aerator with either pliers or the tool included with your faucet. In some cases, you may be able to unscrew the aerator with just your hands. Lower the sink’s plug, in case the aerator’s washer falls out during testing.

With the aerator removed, turn your faucet’s handle to the “on position” and wait for any debris to clear out. Once the water is flowing smoothly without hiccups, shut off the water and reinstall the aerator.

Seal the Back of the Sinkperson washing hands in running water

If nothing leaks when you run the water, you’re ready to seal the backside of the sink. This will prevent any water or moisture from getting between the wall and the sink and causing damage.

To do this, you’ll just need to apply a bead of silicone sealant to the seam between the wall and the sink. You do not need to seal all sides of the sink — seal only the top seam.

Closing Notes

If you’ve made it this far, your new pedestal sink is installed and ready to use.

At this point, you can clean up any mess you may have made during installation and return your tools to their rightful places.

A quality sink should last you a long time. And since you now know how to install a pedestal sink, you’re also capable of fixing it should anything go wrong.

This post first appeared on http://www.theplumbinginfo.com

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