How to install an undermount sink

How to install an undermount sink

Having a cast iron sink is a thing of beauty, thanks to its designer look. It is also strong and durable, and unlike stainless steel it comes in many colors, making it suitable for the bathroom as well as the kitchen. This article shows how to install one. Since sinks are heavy, lifting the cast iron sink into place can be a tough task. Get a friend to help you.

Step 1 – Measure the Sink

Use the template that came with the cast iron sink to make the proper cutout in the counter. If there isn’t a template, measure the sink and create one from scratch. Make sure the counter is suitable to carry the weight of the sink.

Step 2 – Install Basket Strainer

It is best to install the basket strainer and faucet before installing the sink. Mount the basket strainer first. Remove dust and debris from the drain hole with a damp cloth in order to ensure a good seal. Apply a generous amount of plumber’s putty underneath the basket and push it into place. From under the sink, put the large rubber washer over the exposed thread followed by a second thinner washer (all this will have come with the basket strainer). Screw the large metal nut onto the thread. As it becomes fully tightened the putty will ooze out, which will need to be cleaned immediately with a cloth.

Next, the faucet will need to be installed by following the manufacturer’s instructions in order to comply with the manufacturer’s terms and conditions. The installation process varies for each brand.

Step 3 – Install Cast Iron Sink

How to install an undermount sink

To install the cast iron sink turn it upside down while protecting its top surface from damage (also protect the sink and basket strainer if they have already been installed). Squeeze some silicone sealant around the edge of the sink and ease the sink into the cutout in a centered position until it is in contact with the counter. Begin the process of removing the excess sealant to complete the installation. Once the excess sealant has been removed allow it to fully dry—one full day should be sufficient. Excess sealant is difficult to take off if not removed before it dries.

Step 4 – Connect the Sink to the Plumbing

Next, connect the cast iron sink to the pipes and drain. Connect the drain tailpiece to the basket strainer. Use the pipe cutter to trim the ends of the hot and cold pipes. Join them to the faucet using the manufacturer’s instructions.

Step 5 – Check Faucet and Drain Connections

Turn on the main water supply and open the faucet shut-off valves. Check carefully for leaks. If there are any, you may have to retighten everything you installed. Usually, little more than a quarter turn is needed. The cast iron sink project is now complete.

How to install an undermount sink

Undermount kitchen sinks offer the look of class and distinction. We love the combination of undermount sinks with granite countertops. Some shy away from an undermount installation because they are not quite as easy to configure as their drop-in (self-rimming) counterparts. Truth be told, an undermount sink is almost as easy to install, there are just a few extra steps. If you are trying to decide which type of kitchen sink to install, this article will help you determine whether an undermount sink is worth the extra effort.

Prepare Before You Start Your Installation

Before beginning your install, you will need to pick out a few essential items in order to complete the project. Obviously, you need a sink. PlumbersStock offers the best prices on kitchen sinks, and currently, we are running a promotion on Elkay E-Granite sinks. One concern with composite granite sinks is that they may clash with your granite counter, so we recommend choosing a design that contrasts well with your existing kitchen design. As far as tools and items go, you will need the following:

Mounting Sink to Granite in 7 Steps

Once you have picked out the perfect sink and collected all the necessary tools needed you can then begin the installation process.

  1. If you are unable to find the perfect size for the existing hole, or there is no existing hole, have a professional cut out your granite to the exact size to match your sink. Some individuals try doing this part on their own, and unless they know what they are doing, they can mess up a perfect and expensive piece of granite. If you are not sure what you are doing it’s always best to ask a professional for help.
  2. Cut your 2×4 about 1 foot longer than the hole in your countertop. Lay the 2×4 flat over the center of the sinkhole (width-wise) leaving 4” to 6” on either side. Using a bar clamp (I recommend Irwin quick grip Clamps), clamp the sink to the underside of the countertop using the sink drain holes and the 2×4 as your points of contact. No need to tighten your clamps too tight, a snug fit will allow you to adjust the sink into the proper spot. The 2×4 should be able to shift a little along the top of the countertop (with a little encouragement) without damaging the granite (or quartz). Over-tightening of your clamps could damage your sink, so remember, this step is simply for measuring and marking the layout for your under-counter clamps.
  3. Now attach the wing nuts onto the screw heads, look over the placement of the sink once more, if you’re satisfied with the placement you can move on to the next step. Take a pencil and mark each spot where a mounting clip is (i.e.- wing nut location). With the holes marked, you will now want to remove the sink. After the sink is removed, you will drill a hole at each pencil marking using a power drill and ¼ inch drill bit in order for the inserts to be tapped into the holes. Note: be gentle, use a rubber headed hammer so that the granite/quartz is not damaged! Identify where the holes need to be drilled to attach your sink to your granite. Once you have marked where the holes need to be, remove your sink and drill in the designated spots.
  4. Use some rubbing alcohol to clean the ridge. Once the ridge is clean, you can now lay down a small bead (line) of a silicone sealant around the edge. Carefully place and re-clamp the sink into the correct spot.
  5. You can now put the wing nuts on by threading them and carefully tightening the screws. This will anchor the inserts, giving the sink a solid and durable installation.
  6. Pro tip – Use masking tape and mark where the fittings need to be placed on your granite countertop. You will need a 1-1/4 inch Diamond Coring Bit for the appliance holes. These bits are specifically designed for this type of project. Do not try and use a wood drill bit, as you will ultimately damage that beautiful new countertop.
  7. Allow for the sealant to dry (cure) for 12 hours or overnight. After this, you can check for leaks around the rim of the new sink and attach the plumbing fixtures.

Additional Tips

Installing an undermount sink in granite can be an easy job if you know what you are doing. If you have any questions or need any help to be sure to ask a professional. Never just guess as it could cause big problems. Always be sure to read your instruction manual that comes with the sink. Don’t be afraid to ask a friend to help you with the heavy lifting. Save your back! Following these simple tips will help your install go much easier and will make for a much better experience. Let us know in the comment section if you need more help than is offered here. Thank you for choosing PlumbersStock for your learning resource on how to install an undermount sink in granite.

How to install an undermount sink

One of the major problems with kitchen sinks is the water that builds up around it. Water leads to soap scum and mold around the sinks’ rim on top and on the bottom.

Cleaning your kitchen sink's rim is not an insurmountable problem. But constant cleaning gets old quickly, especially when you have so much else to clean in a kitchen.

Other than a relatively few integrated kitchen sinks where the countertop and sink are all a single molded unit, most kitchen sinks are units separate from the countertop. They fall into one of two categories: drop-in sinks or undermount sinks. One clear advantage of undermount sinks is that they help you avoid the water build-up problem.

How to install an undermount sink

Drop-In Sinks vs. Undermount Sinks

Drop-in and undermount sinks both have their advantages and disadvantages. Drop-in sinks are easy to install since they simply drop, or sit, into the countertop cutout and are supported by a rim resting on the countertop itself. But because the rim is raised up above the surrounding countertop, water can spill out onto the countertop.

Undermount sinks have no problems with water spillage onto the countertop since they hang down below the top of the countertop. Undermount sinks are considerably harder to install since their heavier weight is suspended from the bottom of the countertop with clips and adhesives.

This makes an ​undermount kitchen sink particularly susceptible to leaking around the recessed edge of the sink—the seam where the top lip of the sink meets the underside of the countertop. Unless the sink has been installed perfectly, you may well find that water leaks around this seam, spilling water onto the floor inside the sink base cabinet.​

Drop-in sinks (also called self-rimming) drop in from the top and hang via the rim of the sink. In sharp contrast, undermount sinks are those that are secured beneath the cutout opening in the countertop, essentially hanging from the bottom of the countertop.

Re-Sealing an Undermount Sink

Whether you installed the undermount sink yourself or had it installed by a pro, it's not uncommon for leaks to develop in a matter of days or weeks after the installation. When this happens, the problem likely has one three causes.

Poorly Prepared Countertop Bottom

The bottom of the countertop (where it contacts the sink) may not have been cleaned thoroughly. Denatured alcohol should be used to clean off all surfaces prior to caulking. Dust on granite or solid-surface such Corian or Silestone can often compromise the caulking and should be cleaned up before installation.

Insecure Clamps

In other cases, the bottom was thoroughly cleaned but the installation was not secure enough. The clamps or the epoxy, or both, used to secure the sink to the bottom of the countertop were loose enough to cause the caulk to quickly pull away.

Wrong Sealant Was Used

The sink installer may have failed to use a true kitchen sealant. Most undermount sink manufacturers recommend that you use pure, 100-percent silicone sealant for undermount sink installation. Silicone sealants are designed for resilient flexibility and have good adhesive properties. If an ordinary caulk was used to seal the sink, it likely will fail quickly.

How to Fix Undermount Sink Leaks

Though the process is cumbersome, you can likely remedy leaks on an undermount sink by yourself.

  1. Start by crawling under the sink and checking to make sure the clamps are securely holding the sink to the bottom of the countertop.
  2. From inside the cabinet, apply new 100-percent silicone sealant to the seam around the sink.
  3. If you make sure the sink is tightly clamped, then you can try to recaulk and assess if it has eliminated any leaking.

The best solution is to entirely remove the sink and re-seal the sink to the countertop.

Thinking about renovating your kitchen? If so, then our Sink Spotlight series will help you. Up today: undermount sinks.

Sink Style: Undermount

1. Distinctive Features: The edge lip of the sink is mounted below a solid surface countertop, so the sink effectively hangs underneath the counter, as opposed to sitting on top of it; creates a continuous flow from countertop into sink.

2. Countertop Compatibility: Best suited for solid surface countertop materials like granite, soapstone, marble, or concrete. NOT well suited for laminate or tile counters, which have too many weak points along seams and grout lines to support the weight of the sink.

3. Pros: Wipe food scraps straight into the sink (no exposed rim to catch crumbs and dirt); reclaim up to half a square foot of counter space; attractive, minimalist look, easy to clean.

4. Cons: Generally more expensive than drop-in sinks; only works with weight-bearing and water-resistant countertop materials; condensation build-up under the counter can cause mold; faucets must be attached to the countertop or wall.

5. Installation: Proper installation and sealing is crucial to prevent leakage and to make sure the sink is properly supported. (A full sink of dishes gets very heavy. You don’t want the sink pulling apart from the underside of your countertop and crashing to the floor.) Undermount sinks are typically attached with a two-part epoxy adhesive and sealed with silicone caulking around the perimeter. Make sure to get a professional or someone who knows what they’re doing. Most professionals can install an undermount kitchen sink in 30 minutes or less.

6. Price range: $250 – $800, depending on size and material.

Also asked, can I use an undermount sink as a top mount?

undermount as topmount Our undermount stainless steel kitchen sinks do not have the installation holes already drilled and technically can be used in a topmount fashion. We do not recommend this though because the flange (or rim) is flat which leaves a somewhat sharp edge and makes it hard to properly seal.

Furthermore, what adhesive is used for undermount sink? While tile caulking seals the seams where tile, marble or granite meet the upper edges of the sink, using an adhesive at the underside of the countertop ensures a proper installation. The job requires a handful of under-mount sink clips, a tube of silicone adhesive and a few everyday hand tools.

Secondly, what is better undermount or top mount sink?

Drop-in sinks, also called self-rimming or topmount, are still the most common type of kitchen sink. An undermount sink does have a rim, but the rim is not visible because it rests up against the bottom of the counter. The edge of the countertop along the sink cutout is entirely exposed.

Can an undermount sink be replaced?

The short answer is yes it can be replaced. However, I do recommend having a granite contractor do the replacement. The adhesive used to hold the sinks under the top is very strong once adhered.

If you’ve decided to break away from the traditional sink install, and instead are opting for an undermount sink, there are some key things to know beforehand. First off, providing your countertop fabricator with factory specs of your new sink will be crucial. After all, you shouldn’t be cutting the hole for your sink yourself, especially if you’ve decided to install natural stone countertops.

Maybe you’ve spent the last decade as a general home contractor and feel confident you can do this install from start to finish. The thing is, most stone fabricators have highly specialized tools for cutting stone, and if you don’t have such tools, no amount of experience will make up for it.

So step one is picking out your sink before you have your countertops cut and installed. This will allow you the time to get the sink specs to your stone fabricator, which will result in the delivery of a precut slab ready for your specific undermount sink.

With your slab ready to have the undermount sink anchored to it, you can either go for the DIY route or hire a contractor. While installing an undermount sink to a precut stone slab is certainly doable for someone with minimal experience, the benefit of hiring a contractor is that they have likely done the job dozens to hundreds of times. Precision is key to this project, to ensure no leaks or no surprise incidents in which you find your sink in the bottom of your cabinet.

How to Install an Undermount Sink

We’ll walk through the process of installing an undermount sink below, either for personal reference ahead of a DIY project or a better understanding of the job to guarantee you hire the appropriate contractor for the work.

Remove Dust and Clean the Area

Since most undermount sink installs require epoxy to secure the clips, having a clean and dust-free surface is vital to ensuring the epoxy bonds properly with the stone countertop. In the event you opt to cut grooves that will have a clip held into them with a screw, you’ll still need to clean the area where silicone caulk will provide the watertight seal between the sink and counter.

The easiest way to ensure your work area is dust-free is to first wipe down the areas around the precut hole with a dry cloth and then a damp cloth. This will ensure no matter what that all dust and dirt has been removed, and that your counter is ready for silicone and epoxy.

Prepare to Install the Sink

This next phase depends on whether you want to install the sink with the countertop already in place or if you want to attach the sink to the countertop and then install it all in one shot. Doing the install once the countertop is installed really depends a lot on the size of your under sink cabinets. In many cases you’ll have to drop the sink in before putting the countertop down, and in others you’ll be able to finagle the sink in through one of the cabinet doors.

Now pre-installing the sink will likely be the easiest option, as you’ll rely on gravity to attach the sink rather than clamps. Regardless of when you decide to attach the sink, the process will remain relatively the same.

Attaching the Sink Under the Counter

We’ll focus on the more difficult and involved install, which is installing the undermount sink after the countertop has been set in place – the other option is simply a couple less steps. For this you’ll need a 2×4 longer than the width of the cutout for the sink as well as one or two clamps, depending on if your sink is a double or single bowl.

Once the sink is resting in the cabinet below the cutout in the countertop, what you want to do is lay the 2×4 across the cutout. Then lift the sink up to the cutout from below and secure in place with the clamps by attaching one end underneath the drain hole(s) and one to the 2×4.

While positive and negative reveals are options, the only option you should go for is the flush mount reveal in which the edge of the sink is aligned with the edge of counter cutout. The reason why is obvious: a positive reveal will create more areas that will need cleaning while the negative reveal will guarantee you chip part of your countertop pulling a pan out of the sink. A flushmount or neutral reveal will make life and cleaning a lot easier.

Once the sink is clamped in place, get underneath and ensure it’s a snug fit. After you’re confident with the placement, lower the sink enough to apply silicone caulk around the rim of the sink. Then crank the sink flush against the countertop, lock the clamps, and let the caulk dry.

Finalizing the Undermount Sink Install

Now that the sink is locked in place with clamps as the silicone dries, it’s time to add the metal clamps that will make sure the sink is locked in place for as long as it will be in use. To do this, you’ll need a two-part epoxy and special clamps with multiple holes cut into the mount.

Apply the epoxy around the corners of the sink and then quickly press the metal mount into the epoxy so that it oozes through the holes. Make sure the mounts are positioned correctly so that they lock over the edges of the sink. Once the epoxy dries, your undermount sink is good for use. Now remember, you’re looking at about 24 hours before all the appropriate compounds set completely. Even if the epoxy and silicone look dry, don’t expose them to water until after 24 hours.

After all, undermount sinks can last a lifetime if installed properly, so don’t let impatience ruin your sink and cabinets all because you wanted to play with your new sink sooner than you should’ve.

Do not you have clips or mounting hardware to secure your sink?

Are you afraid of installing a sink without clips?

It is possible to install undermount sink without clips or mounting hardware. When you are missing the clips to install your sink, you can avoid drilling the hardware mounting holes in your granite.

In that case, you can use silicone adhesive and epoxy to install the sink on your kitchen countertop.

Install Undermount Sink Without Clips | 5 Simple Steps

How to install an undermount sink

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  1. Preparation
  2. Silicone Adhesive
  3. Installation
  4. Cleaning
  5. Epoxy

Let’s discuss step-by-step details.


Before you install a sink on your kitchen countertop, you need to take preparation. First, you need to clean both the countertop surface and the sink surfaces.

Wipe the surfaces with a clean rag and remove all the dirt, grease, and grime that could obstruct the process of the installation.

If you use acetone, It will help you to remove all the dirt from the surfaces.

You only need to follow all the instructions that are included on the acetone bottle when you use it with a clean rag on the surfaces of your sink and kitchen countertop. After applying the acetone, let it dry for a few minutes.

Silicone Adhesive

Several adhesives are available on the market that is used for kitchen sink installation. The material of an adhesive is used to seal around the sink after installation. It is usually used around the contact surface of the sink.

A sink has a contact surface that allows the countertop to make a connection.

For an undermount sink, the contact surface is around the 1-inch lip on the same side as the sink opening. With the help of the adhesive, it adjusts with the countertop.

On the other hand, you need to apply the adhesive to the underside of the perimeter of the sink opposite the sink openings. When you purchase an adhesive, you have to get the best glue so that your sink adjusts with the countertop perfectly for a long time.


If you want to install an undermount sink, you need to install it to the bottom of the countertop.

First, you need to place the sink on the countertop then lift the sink until it makes contact with the downside of the countertop. Look how much drain openings you have and then place one or two bar clamps and a cross brace.

One end of the bar clamp grabs the bottom of the sink, and the other end attaches to the cross brace.

You have to adjust the sink position and need to tighten the bar clamps until the sink is snug with the countertop. Installation of a drop-in sink is easier than undermount countertop.

You need to apply adhesive under the lip of the sink and adjust it in the proper location. After adjusting the sink into your countertop, then your sink will be installed.


After installing the sink, you need to clean the sink and the countertop immediately. You have to remove the excess sink edges and dirt from the surface of them. When you tighten the clamps, some silicone seeps out from under the sink edges.

Before removing the excess silicone, joint the sink lip with the countertop with your finger to make sure that they adjust perfectly. If you think you need to add some additional silicone, add more and remove the extra silicone before it dries.

After cleaning the surface your sink will look perfect, clean, and shiny.


Finally, you need to add additional support to incorporate garbage disposal. It is important to add additional support when you install an undermount sink without hardware.

When you fill the sink with water, the garbage disposal sides can be very heavy for this reason your sink may detach from the countertop.

To reduce the chance of detaching the sink from the countertop, you need additional support.

To adjust small blocks of granite or acrylic material to the bottom of the countertop overlapping the lip, you need to add a two-part epoxy. The epoxy is a rapidly setting material that allows you to connect the plumbing immediately after installing the sink.

For the drop-in sink, you do not need to add extra support if the sink is supported by the countertop.

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By following all the steps, you can install an undermount sink without clips. It is not much difficult to install, you just need to be more careful when you are installing the sink.

After installing it, you can accomplish all your home activities in the sink.

How to install an undermount sink

As one of the major fixtures in our bathroom, the sink is a key design consideration. Of course, the look is important but you also need to consider how the sink is installed. In this article, you’ll get to know everything about Undermount sinks and also a detailed guideline on How to Install Undermount Bathroom Sink.

For the last few years, Undermount sinks are getting very popular for their looks and easy installation process. It gives a clean look and works great for kitchens or bathrooms. Now with more perfection, Undermount sinks will go years probably a lifetime without having any issues.

These sinks are very easy to install and replace but very sophisticated to use. It’s suggested to use help from professionals or you can do it by yourself. But you need to have some knowledge about the installation process. You’ll find endless marvelous designs, many custom sizes, and top-quality materials in the market if you choose an Undermount sink unlike any other.

Things You Need to Know Before Purchasing

Undermount sinks are usually installed below the cutout in the small bathroom vanity top. The cut edge of the hole in the vanity will be visible in this type of sink. So it’s important the top is a solid material and not a material like laminate or tile. Undermount sinks typically do not have pre-drilled holes for the faucet.

Instead, the faucet is installed into the vanity top through the holes; drilled between the sink and the wall. Before you purchase an Undermount sink you need to be careful that-

  • Your vanity top has to be strong enough to hold the weight of the sink
  • Your vanity top has to be big enough according to the size of your sink
  • The sink has to be made of the right material for installation
  • You should look at the color and design of the sink and choose one that will complement the whole bathroom design

Kind of Under-Mount Sink

There are different kinds of materials used to make Undermount sinks. You can choose any of these material-based sinks for your bathroom or kitchen. Such as-

  • Stainless steel Undermount sink
  • Enameled cast iron Undermount sink
  • Fire clay Undermount sink
  • Solid surface Undermount sink
  • Still Granite Undermount sink
  • Cultured Marble Undermount sink
  • Ceramic Undermount sink

Tools Needed for the Installation

The things that you need for the installation are-

  • Undermount sink
  • A measurement tape
  • A silicone adhesive
  • A paper towel
  • Few pieces of wood

Step by Step Guideline of Installation

Follow the detailed description to install an Undermount sink in your bathroom-

  • First, make sure which way you have to install your Undermount sink
  • There are two sides- one deep side and another side will be shallow
  • Always install the shallow part towards you
  • That way it facilitates washing your hands
  • Measure the inner depth of your cabinet to the underside of the countertop
  • Take a piece of wood that you’ll use to hold the sink up while using adhesive
  • Make sure your adhesive smells like vinegar because that means it going to be a good adhesive
  • Place your sink underneath the countertop
  • Apply your silicone adhesive on the edges of the sink in the quarter-inch bead all the way around
  • Be very careful with adhesive so you don’t get in touch with the silicone
  • Make sure your bead is nice and continuous because it’s also a sealer that will stop the water from getting into the cabinet
  • You can keep toilet paper close by in case to need to wipe
  • Now grab your sink upwards and lift it into position
  • Use the piece of wood to give the sink support from underneath
  • Manipulate the front and the backside of the hole
  • Give it a lilt and squeeze it in place
  • Make sure the sink’s not going to fall out
  • Be sure that the gaps are consistent around
  • Wipe off the extra adhesive that might come out from the sides
  • You can add some more pieces of wood for compression if you need
  • Theres’ another way that you could do this is by putting a piece of 2×4 with a hole drilled here
  • You can buy at the store a threaded rod about half an inch
  • Then you can get galvanized bolts for the half-inch rod
  • Then you can put a little piece of wood underneath with a hole in it as well
  • Slid it over the rod, tighten the nut on
  • From the top, you’ll lift the sink into place and you can thread the rod
  • Use a wrench to put the compression that’s going to do the job easier
  • Leave the sink like this for few days to dry-down the adhesive completely
  • Now your sink is ready to use!

So now you know how an Undermount sink looks like and How to Install Undermount Bathroom Sink. We are sure once you start using the Undermount sink at your home you’ll never go back to another one. These sinks will definitely be a statement piece for your home decor. Make your bathrooms look classy by purchasing stylish Undermount sinks.