Most always, you deal with wall plumbing when it comes to bathroom sinks. The rationale is obvious: wall plumbing means a vanity and more storage space. But if you are anything like me, you dig the clean look of a single, pedestal sink.
Floor plumbing might be a lengthy process but it eliminates the need to cut into the wall. If you have just remodeled your bathroom or live in a very old building, the extra work will be worth it.
Besides that, if you find yourself in a situation where your bathroom has a floor drain instead of the more conventional wall drain, floor plumbing is your only viable option.
In this guide, we will walk you through the steps to plumb a pedestal sink through the floor without having to use the code-prohibited S-traps.
For mounting a pedestal sink to the floor, irrespective of the floor type, you will need the following things:
- A measuring tape
- Safety glasses
- Adjustable wrenches
- Utility knife
- A bucket
- Handsaw/ circular saw
- Socket wrench
- Drill and drill bits
- Silicon glue
- Hanger bolts, slip bolts, washers, etc
- Wall paint and drywall supplies to repair the wall
7 Steps to Install a Pedestal Sink with Floor Plumbing:
Step 1: Removing the Old Sink
There can be both hot water and cold water supply lines to your bathroom sink. Turn off both and let the water already inside the faucet piping run out.
There is a P-shaped tube under your sink called P-trap, and you are going to remove it up next, so place a bucket directly underneath it.
Open the slip nut that fastens the P-trap to the rest of the structure. Now, the P-trap can be removed. Let any water in the pipe drain into the bucket.
Push the bucket under the water lines, and disconnect them next. Let any excess water drain into the bucket.
Next, you will remove the old sink.
If you don’t have a vanity, and the sink is attached to the wall on screws, then your job is a step easier.
Prop up the sink so it doesn’t fall when it is loosened from the wall. Use the wrenches to unscrew the sink and remove it.
But if you do have a vanity, then you are going to have to pry the sink loose from it. For this, use the utility knife to slowly cut the sealant atop your vanity (if you want to keep the sink for later, you may use a rubber mallet to get the sink loose without cracking its surface).
Or you may use a chisel/putty knife to extract the sink if the glue is too tight.
Step 2: Take the Measurements
Once the sink is loose, remember that it can be heavy. Seek help to remove it.
Now, unscrew the vanity and reinstall the P-trap to the plumbing.
Measure the following distances:
- From the P-trap to the floor
- Between the two water supply lines
- From the floor to the mirror (if any)
These measurements will determine what height and width your new pedestal ought to be. Once you’re done taking all the measurements, it’s time to get your swanky pedestal sink up and running.
Here’s how to do it:
Step 3: Primary Assembly
Here, by assemble, I mean loosely assemble. Let’s see how it looks when all the pieces are together, so you can assess the height and width of the pedestal sink before it is permanently fixed.
Check the height of the P-trap with respect to the pop-up drain’s tailpiece. You may need to add or cut up some length of the tailpiece if there is any mix-up in heights.
Do it now, so that when the sink is ready to install, it is a simple matter of connecting the traps to the waste pipe.
Step 4: Installing Optional Support Board for Extra Stability
Whether or not the pedestal sink that you bought requires extra support will be clearly mentioned in the manual. Read it first.
If you have drywall, most often than not, a support board is essential.
Here’s how to install it:
- Mark the centerline of the sink so you know the exact place where it needs to be fixed. This means the water lines should align with the sink’s faucet holes.
- Mark the height of the pedestal sink on the wall. This is where the sink’s mounting bracket would attach.
- Cut up the drywall in that dimension. Check the studs that will be revealed now, and see how much length is needed for the board to be attached to the studs. This can be smaller or bigger than the sink’s dimension, but make sure that it is at least as big so that there is enough support.
- Cut up a piece of wood to the dimensions that you have marked on the studs.
- Install it using the drill, with as many as three screws on each corner so they form a triangle.
- Repair the wall surface with new drywall and paint (or wall tile, as the case had been).
Step 5: Prepping the Surface for Installation
You know where the mounting board is inside the wall. The central line of the pedestal is already marked. Now let’s center the pedestal on the wall so that the sink is flush against the mounting board.
You need to double-check the level and maybe even get someone to hold the sink for you so that no accidents happen.
Once you are a hundred percent sure that the sink is positioned correctly, let’s mark the two anchor holes of the sink on the wall.
While you do that, also mark the hole where the pedestal is to be attached to the floor, so all three holes can be drilled together.
Keep in mind that the hanger bolts you use should be long enough to remain at least an inch into the bathroom. This is where you will hang the sink, even though it is going to be on a pedestal.
Confused? Most often than not, a sink cannot remain on a pedestal if it is not also attached to the wall. This is why we already installed a mounting board in the bathroom.
Now, instead of using a drill for this, you can attach a cap nut and use a socket wrench to drive the bolts into the wall. Make sure that an inch of their length remains outside the wall.
Step 6: Plumbing the Sink Drain and Faucet
Here, you will fix the faucet and the sink drain before installing it in the bathroom. This is what you do for the drain:
- Wipe the sink’s drain hole clean.
- Apply silicon glue to the underside of the flange. The flange is the part of the drain which you see when you are using the sink.
- Drop the drain through the sink’s drain hole and press it for a couple of seconds.
- Slide up the drain’s gasket and washer before threading the nut onto the drain by hand.
- Tighten it using a wrench--just enough, but not too much so that it cracks.
- Wipe off any excess glue that may be seen atop or below the drain.
The same is done for the faucets. The difference is that there can be several holes on the sink’s lip where the faucet is supposed to go, so you need to know this:
- Four holes mean three of the left holes for the faucet (hot and cold water valves plus the spout) and one on the far right for the spray hose.
- Two holes mean that you can install a single faucet and one spray hose.
Step 7: Mounting the Pedestal Sink
Now that the sink is ready with the faucet and drain, let’s mount it on the hanger bolts. Secure it using washers and cap nuts. Tighten it properly, but not too much so that the sink cracks.
Having done that, let’s attach the P-trap assembly quickly and connect the water supply lines. This is what you do:
- With the help of someone else, hold the sink so it doesn’t slip off the wall.
- Install the P-trap to the tailpiece of the sink’s drain, using slip nuts.
- After hand tightening the slip nuts, do an extra turn using hand pliers.
- Connect the water supply lines to the appropriate valves of the faucet.
- Check for leaks by opening the supply lines.
- If there are leaks, apply some plumber’s putty and tighten the nuts.
Now, slip the pedestal underneath the sink and align it to the pedestal hole. If you need to slightly raise the sink to slide the pedestal in, do it. Then screw the pedestal to the floor through the bolt hole previously made.
Check to see that the sink is level, and adjust if need be. Tighten the hanger bolts’ cap nuts and ta-da!
You have successfully installed your pedestal sink!
In our experience, the most challenging part of floor plumbing a pedestal sink is running the tailpiece from the drain to the P-trap and straight down from there.
Running the drain correctly is super important, so don’t rush it up. The best part about pedestal sinks is that they don’t ruin the vibe of your bathroom with ugly exposed pipes.
Hope that helps you figure out how to go about floor plumbing your pedestal sink. Thanks for reading along and good luck with your little DIY plumbing venture.