How To Attach Sink To Vanity? Follow Step-by-Step Guide

If you are considering attaching the sink to your old or new bathroom vanity, you should find the best way that can be easily handled at home. This article is all about how to attach the sink to the vanity.

Installing the vanity base is simple, but attaching the sink and placing the vanity top along this needs extra expertise and physical strength. No matter what type of sink you attach, its installation process requires some plumbing work. Sometimes you may need to hire professionals to tackle the task. However, if you deal with the whole process carefully and intelligently, you will never need to hire professionals. It will not only save the cost of the remodeling project but also will make you confident to handle the task by yourself.

If you decide to handle the task independently, you might need a helping hand while placing the countertop on the vanity base. Vanity tops are heavier than they seem. There is always a chance to slip the top when dealing with the process alone, so it is better to take the help of your family member or a friend. The rest of the process requires a perfect guide and the tools you must collect before installing.

Read the given process before attaching and installing the bathroom sink.

Detailed method to attach the sink to the vanity

Required materials

  • Plumber’s putty
  • Sink assembly
  • Sink installation kit
  • Rag
  • Sponge
  • Silicone caulk
  • Caulking gun
  • Supply lines/pipes
  • Wrench
  • Plumbers tape
  • Glue
  • PVC pipes

When you gather all these materials, start the process and secure your sink quickly by reading the complete guide.

Step 1: Start assembling the sink

For assembling the sink, turn it over and securely place it on a solid surface. While handling the countertop, you need to show some extra care because if your top accidentally falls on a solid surface, you can lose it by damaging it. To assemble your sink, there is a need for a stable surface so you can place your sink comfortably.

How To Attach Sink To Vanity

Find a highly sturdy table or set up two sawhorses and place the countertop on top if you need a steady platform to work on. To prevent cracking or getting scratched on the countertop surface, get five to ten soft clothes and place them between the sink and the sturdy surface.

Most vanities come with a preassembled sink that you don’t need to fix. But if your sink is not assembled, you need to follow the whole process, and sometimes you might need to buy a separate assembly to attach the sink to the vanity.

Step 2: Prepare the sink flange

To prepare the sink flange, apply the plumber’s putty to the flange’s internal rim. Generally, a sink flange is a gleaming metal component that can fit in the bottom of your basin. It is the only component with the finish, and its inside part is threaded near its bottom. 

You can find a can of putty from the market to prepare it. Take a small chunk of putty in your hands and mold it. You need around the size of your palm’s worth of putty. Rub the putty together to form a thin 5”–6” length.

This molded putty should be tightly rolled over the sink flange’s bottom rim and pressed against the edges. When you put the other parts of your sink together, the plumber’s putty will keep everything in a single place.

Although a plumber’s putty has a strong fragrance, it is safe to handle even without gloves. Simply mold it in your hands and wash your hands. Don’t be afraid about your putty toughening as you work because a plumber’s putty takes a long time to dry.

Step 3: Thread the rubber gasket

The next step involves wrapping the thread on the rubber gasket over the lock nut on the drain pipe. The drain pipe is the metal pipe connecting the sink flange to the pipes under the vanity. It will have a little lip in the center, one end with threading and one end without threading.

Hold the pipe so that you can see the top threaded part. The metal lock nut should be slid over the pipe and let drop to the lip after fitting the rubber gasket over the lock nuts. These lock nuts will screw into the drain pipe’s threading during assembly. It helps compress the rubber gasket into the sink base, forming a tight seal. Sometimes you might need a third or fourth gasket to cover the threaded rubber gasket.

Step 4: Screw the drain pipe

After threading the rubber gasket, attach the drain pipe to the sink flange by screwing it. Hold your sink flange in one hand so you can see the putty in front of you, and slightly fit the bottom part of the sink flange into the sink hole and pull the pipe through the opposite side. After fixing the sink flange, rotate the pipe in an anticlockwise direction until the threading of the flange is hooked.

You need to twist the drain pipe until the putty touches the rim. When you find difficulty in twisting the pipe while fixing the flange, you will get the idea that the putty has made contact with the pipe. This task may be tricky as you hold the two parts simultaneously, one above and one under the sink. You can ask for help from your friends or family member.

Step 5: Tight the rubber gasket

To tighten the rubber gasket against the opening, you need to rotate the lock nut clockwise. Once you have placed the threading in a single position, you can release your grip on the sink flange. While holding the pipe with your left hand, tighten the metal lock nut by rotating it clockwise. You should keep tightening the nut until you cannot turn it further.

To seal the rubber gasket into the sink base, firmly screw the lock nut. The process requires physical strength and strong grips to hold and secure the sink flange and drain pipe. If it has flat edges, you may require channel locks or a wrench to turn the lock nut. When you tighten the pipe, your basin flange will tighten into the sink hole at the bottom of the sink.

Step 6: Check the level of the countertop

Whether the level of your countertop is perfect or not, you need to check it by placing the top of your vanity on the base of your vanity. Lift your countertop by griping firmly from both sides of it. Countertops have high weights, so you need help lifting and placing them on the base. However, set the sink where you want to place it by gradually lowering one side.

Remove the counter if it properly fits between the cabinet and the top of the base. For some reason, if it isn’t level, then you can make it by fitting shims under the countertop. Secure the shims in one place by applying the glue.

Step 7: Apply silicone on the edges of the cabinet top

After checking the level, apply silicone caulk before placing the countertop on the base. Put aside the countertop nearby your vanity. Take the silicone caulking gun and insert a silicone caulk tube into this. Cut the tip of the tube up to one inch. Apply the thick layer of silicone on the top of the cabinet by squeezing the tube with the help of a caulking gun.

Carefully apply the silicone caulk on each side of the countertop. Remove the excess amount of silicone with the help of a sponge. In the case of an undermount sink, you need to support the countertop while the applied silicone is drying.

Related Guide: How to install bathroom vanity?

Step 8: Place the countertop on the vanity base

Now you can lift the countertop and place it on the cabinet top. Place it in the correct position. If you can, ask a buddy to assist you with putting the countertop on the vanity base because the more precisely you put the vanity at first, the better. 

Adjust the countertop as necessary after lowering it into position. Allowing one end to fall first and slide the countertop into position against the wall as you slowly lower it. You need to perform this task faster because the applied silicone can dry within five to ten minutes.

Step 9: Fill the gaps

When carefully placing the countertop on the cabinet base, bend over with a caulking gun. Apply the silicone caulk where the overhang meets the vanity to fill the gaps. Smooth the caulk with the help of your finger, and wipe out the extra caulk using a paper towel.

You can apply the caulk between the vanity and the wall to stop water from sliding under the vanity. You may also apply silicone caulk to the top and side where the counter meets the wall. If there is no gap between the wall and the vanity and your vanity is tightly set against the wall, then you can skip this. Leave the vanity for up to 24 hours so the silicone can dry.

After removing the extra silicone, clean the countertop and leave the room. Avoid touching or moving your vanity or countertop while the silicone is drying.

Step 10: Get the PVC pipes for connecting the plumbing

After attaching the sink to the vanity, you need to get the PVC pipes to make it operational. You will find different size pipes. To get the proper measurements for your sink pipes, you need to measure the diameter of the aperture at the bottom of the drain pipe.

The diameter is probably 1.5 inches unless you have a unique or custom vanity set. A J-pipe is also required to maintain a small amount of water in the pipes and stop odors from rising, and a final length of pipe is required to connect to the drain in the wall.

Don’t go for metal pipes; they are challenging to handle while working with them and can rust with time. Besides, check whether your drain has threading or not. If not, you’ll need a sleeve to cover the joint between the two pipes. Instead of smooth connections, choose pipes with threading. PVC adhesive is necessary for smooth connections, and the entire system must be replaced if there is a leak.

Step 11: Attach the washer or rubber gasket

Each pipe has a threaded part where you must attach the washer or the gasket. Under the vanity sink, set your pipes after opening the bottom cabinet doors. You will find the washer and the gasket according to the types of pipe set you purchased from the market.

Sometimes you need to screw them together for attaching. If your pipes come with washers and gaskets, place each gasket on top of each hole with the threads pointing up. Insert a washer inside the lining of the gaskets. Generally, a washer is a plastic ring that encircles the pipe. Its purpose is to close the gap around the threading where the gasket and pipe joint are.

Step 12: Attach the straight pipe to the drain pipe

Start assembling the drain pipe by attaching the straight pipe to the drain pipe. The straight pipe at the top should be screwed into your drain pipe. Push the pipe up to the drain pipe while the washer is on top of the gasket, then twist the gasket clockwise. To attach the straight pipe to the drain pipe, rotate it as firmly as you can.

Sometimes you might have seen other plumbing configurations where the straight pipe just circles the drain pipe without any seal. These configurations aren’t ideal because a pipe stoppage could result in water gushing into your vanity.

Step 13: Attach the wall connector to the concealed drain line

After fitting the straight pipe, examine the pipe in your wall from where the water will exit. If this drain pipe has threading, you can screw the pipe into the drain line as you fix the straight pipe into the drain pipe. In other cases, when the drain line does not have threading, then you need PVC glue.

Cover the unthreaded part of the pipe with the glue, slide it into the PVC sleeve, and again apply the caulk or glue to secure the joint. This PVC sleeve is a small plastic pipe designed to join the two pipes with a smooth surface.

Step 14: Attach the J-pipe

To complete the drain assembly, install your J-pipe. By using the washer and gasket, screw the trap into the drain pipe. While screwing the washer and gasket, ensure that you have some space to work, don’t tighten it all the way. After partially screwing the J-pipe into the drain pipe, turn the pipe around and align the drain line with the other end of the J-pipe using the threading slack.

Step 15: Attach the supply line to the faucet

Faucet assembly has some flexible tubes called supply lines, which are generally screwed into water supply lines and sink faucets. It doesn’t matter which line goes into either pipe because the supply lines are similar. Simply tighten each line until it is unable to be turned anymore.

Fasten the other ends of the supply lines into the faucet after inserting them into the counter’s holes for the faucet. You can use the wrench to tighten the supply line connectors to make a strong attachment.

Step 16: Install the faucet

Install the faucet into the given position and use the caulk to secure the faucet in one place. Apply the silicone caulk at the bottom of the faucet and fix it firmly. The pre-assembled nature of faucets makes installation incredibly simple. In case of a pop-up drain, fasten the clevis strap to the lift rod with the help of a screwdriver.

Insert the pivot rod through the clevis strap and wrap a clip around its opening on its opposing side, which will help to hold them in one place. Pop-up drain installation is not that difficult. It only requires passing the pivot rod through the strap. Without the pivot rod, you cannot install the pop-drain assembly.  

Step 17: Test the pipes for any leakage

Finally, for checking any leak, you need to test the pipes by running the water for up to 20 seconds. Turn on the valves on the supply lines for running the hot and cold water supply lines. To properly check the leakage points on the pipes, run your hands along them. If you find some leaks, stop the water flow and seal them up with putty or plumber’s tape. Put a towel or bucket under the sink to prevent water leaks.

Method to attach the vessel sink

The above method to attach the sink can apply to all other sinks. But the method for installing the vessel sink is different as this type of sink sits on the surface of the vanity top. Today, the modern bathroom has mostly this type of sink. A vessel sink improves the bathroom’s functionality and enhances the aesthetics of any style of bathroom.

Considerable points before buying a vessel sink

Before buying the vessel sink, you need to decide what type of vessel sink you need. Whether you are planning to place the vessel sink on the old vanity top or the new bathroom vanity, consider the available space for placing the vessel sink and the point for installing the faucet and drain assembly. Finding the location of the faucet is the most essential while mounting such style sinks.

If you don’t find the desired location for installing the faucet, you might need to buy a new countertop. With a vessel sink installation, holes must be made in the vanity top for the sink drain and, if necessary, the deck-mount type of faucet. The holes for the faucet must be located at the right point to get a coordinated and desirable look.

Before installing the sink, ensure you have a suitable drain assembly fitting. In most the cases, this fitting is the anchor to hold the vessel in one place besides the draining purpose.

If you want to install the glass vessel sink, you need a mounting ring that can be placed on the countertop to hold the vessel sink in one place.

After considering the points, attach the vessel sinks to your vanity.

Position the vessel sink.

A mounting ring or gasket can be placed between the sink and the countertop to place the sink on the vanity top. If your sink already has a mounting ring, place it over the vanity top before setting the vessel sink on the surface. In other cases, you may need silicone caulk to seal the vessel sink to the countertop.

Insert the drain flange and tailpiece

.For inserting and fitting the drain flange, you need to run the beads of putty around the bottom of the bottom surface of the drain flange on the drain fitting. If your sink has a rubber gasket, then place it on the flange’s lower surface.

Carefully slide the tailpiece of the drain fitting through the countertop hole and push it downwards into the drain opening. Use a rag to remove any extra plumber’s putty from the area surrounding the drain flange.

Secure the tailpiece

Apply a small amount of silicone caulk on the rubber gasket. Starting from the bottom of the sink, push the seal toward where it will go into the countertop hole and up around the drain tailpiece. Then after threading the mounting nut, you need to thread the friction ring on the tailpiece. Firmly tighten the mounting nut using the tongue-and-groove pliers. Do not over-tighten it to protect your sink from getting any damage.

Finish the drain assembly.

With the help of a slip nut and washer, attach the P-trap to the sink drain tailpiece, making it temporarily firm. After this, you can attach a trap arm between the P-trap outlet and the wall drain pipe using slide nuts. Attaching the trap arm may require a slight downward slope toward the drain line.

You should use a hacksaw to install a tailpiece extension or trim the trap arm to fit, depending on how the drain is set up and where the branch drain opening is located. When you fix all the drain components in one place, then tighten the nuts with your hands or tongue-and-groove pliers.

Carefully examine for any leak.

Run the water by turning on the faucet to check the leaks under the sink. You can also fill the sink up to the top and perform a thorough volume test to ensure no leaks under typical operating conditions. Typically, merely tightening the slip nuts a little bit more will stop minor leaks at the slip nuts.

If you find any leakage from the sink’s base onto the countertop or around the rubber seal, you fail to place the drain fitting in the sink’s base correctly. In this situation, you must unscrew the drain and repeat the process while paying particular attention.


Which type of adhesive secures a sink to a vanity?

To secure the sink on the vanity, you always require a unique adhesive material that can stand under the water flow. For this purpose, silicone caulk is the best material to hold the sink onto the vanity under different conditions for extended periods. Today you can also find the specifically designed silicone caulk to secure the sinks over the vanity tops.

It has the ability to bond on the ceramic surface. However, for granite, you require advanced glue, which is also made from silicone.

Can silicone hold an under mount sink sufficiently?

Yes, it can hold the undermount sink only if it is 100% pure. Most sink manufacturers advise installing the under-mount sinks using 100% pure silicone caulk. Silicone caulk has good adhesion qualities and is made to be flexible but robust. If you use the regular caulk to seal the sink, it will probably fail to hold the under-mount sink shortly.

Final words

Until now, you might find the best way to attach the sink and fix the plumbing fixture. Attaching the sink is a challenging task and cannot perform lonely. You might need the help of others. The method for installing the vessel sink is slightly different, as mentioned above.

However, if you decide not to hire a professional, you need special attention to reading entire the entire method given above. With some effort, you can attach your sink on your own and can save money by hiring a professional. Still, if you need help with how to perform the task, it is better to pay the professional than lose your precious sink or vanity top.