How to Install a Drop in Cast Iron Kitchen Sink

There are many challenges on how to install a drop-in cast iron kitchen sink. You might not have much experience with sink replacements or maybe you do but need a refresher. Whichever the case, we got you covered on how to install a cast iron sink.

Cast iron sinks are designed for rustic décor. They’re strong and durable as well. Compared to stainless steel sinks, they come in various colors to suit any theme of your kitchen or bathroom.

A cast iron sink is heavier than your average sink. Luckily, the installation process isn’t any more complicated than the standard way. It might get a little more complicated if you choose to build a support frame, but a frame only adds an extra layer of protection.

7 Steps to Install a Drop in Cast Iron Kitchen Sink: 

Whether you want to install heavy cast iron sink alone or with help from a friend, you’ll need to know what to do. The same goes if a professional does it for you. You might have some curiosity about how they do it. This step-by-step guide will teach what you need to do.

Step 1: Measure the Sink

Before you buy a cast iron sink, you’ll need to measure it to make sure it will fit in the sink hole. You’ll want to measure the width and length of the bowls and the lip around the sink.

You don’t need to include the lip in the countertop because this will be your support for the sink. It’s wise to measure the depth of the sink too to ensure it doesn’t interfere with your lower cabinet. Measure and mark the cut for the sink hole.

Step 2: Cut Out the Sink

First, put on your safety goggles to protect your eyes from any debris. Next, cut the sink hole out using your markers from step one. Use a spade bit to drill a hole on any part of the marker.

This will be your starting point to fit a jigsaw. Not doing so will result in broken blades when trying to cut the sink out.

The key aspect of this cut is to leave an area for the lip. You’ll need the lip for the edges and to hold the sink in place.

Step 3: Place Extra Supports 

We cover this more in-depth below because it’s technically an optional step. You don’t need supports if you don’t want them.

However, it’s recommended because should something happen to your cabinet, your sink will go with it. Again, this step is optional but highly recommended. If you want support frames, explore the section below.

Step 4: Install a Basket Strainer

It’s recommended to install a basket strainer and a faucet before you install the sink itself. Mount the strainer and clear any debris from the drain hole to ensure it seals properly. Use plumber’s putty undeath the basket and push it into place.

From under the sink, put a large rubber washer over the thread and the thinner washer. You don’t need to worry about parts because it comes with it. Screw the nut onto the thread.

You may notice putty come out the tighter you make the nut. Clean any excess. To install the faucet, follow the manufacturer’s instructions because they vary.

Step 5: Installing a Drop-in Cast Iron Sink

First, decide whether you need plumber’s putty or caulk for the installation. Flip the sink upside down on a towel or some protective surface to avoid scratches or damage. Protect the basket strainer to prevent damage.

Place the caulk or putty around the edge of the sink hole and don’t forget the lip! Ease the sink quickly but carefully into position. This step is very time-sensitive because caulk and putty dry quickly. It should come evenly in contact with the counter, and you might even have some excess putty or caulk.

That’s okay! You can scrape the excess off once you position the sink where it needs to be. You can remove it with a putty knife. You don’t want to wait until the excess sealant dries before you remove it because it’s very difficult. Let the sink completely dry for a day.

Step 6: Connect the Plumbing 

If you made a support frame, mind the hole(s) you made for these connections and attach them through it. Connect the sink to the pipes and the drain. Make sure the drain tailpiece and the basket strainer are connected.

You may have to use a pipe trimmer at the ends of the hot and cold pipes. Attach them to the faucet. It’s recommended you use a thread sealer on any threads before you screw the lines to sink or connections to prevent leaks. You may want to replace any old washers with new ones too.

Step 7: Check If Your Sink Works Properly 

Turn on your main water supply and open shut-off valves. Turn on the faucet for a few minutes and observe any leaks. If there are any leaks, check where it’s coming from. Immediately shut off the water. You might even want to turn the valves and main supply off if the leak is bad enough.

Retighten the areas where the leaks are. Usually, you will need an extra quarter turn and you’re good to go. Turn the water back on and observe for any more leaks. No more leaks mean you’re done and free to use your sink!

Build a Support Frame for Cast Iron Sink 

Cast iron sinks are much heavier than a standard drop-in sink. Since it’s heavier, we recommend extra support to prevent any issues that may arise with the kitchen countertop.

However, the supports are optional but to cover a full installation with this guide, we will include the extra support steps.

Step One: Take Measurements

Measure the depth of the sink and mark it on the sides of the cabinet beside the sink hole for brace placement. Plywood will fit atop these braces. Make sure to measure and make markings from the back cabinet to the front to give support to the whole sink.

Step Two: Create the Frame

Cut a piece of 2X4 wood to make two support beams. Place the newly cut supports on the marked template below the sink hole. In the event your sink doesn’t come with a template you’ll have to create one from scratch.

Drill a hole through each support beam based on the listed markings. Use a wood screw to hold the wood up to your template and repeat this on the other side. Let the supports hang while you check the level across the pieces. Once you have level pieces, drill three holes for each. Secure the supports with three wood screws into the cabinets.

Step Three: Support the Braces

You’ll want to find a middle piece between the two braces and cut it so that it fits as perfectly flat and close together as possible. Check the level of the piece to ensure there’s not any incline or decline. Drill a diagonal hole into the middle support brace to the side support braces. Use a wood screw to secure it in place.

Step Four: Add Support for the Cabinet Area

Measure and mark plywood so it will fit level with the support system. You may want to round down measurements to ensure it fits inside the cabinet. Cut a hole (s) for the water line system. You don’t want to cut a hole directly into the middle because the middle supports the sink. Drill the holes and use screws to attach them to both sides of the support beams.


1. Can a laminate countertop support a cast iron sink?

Yes, depending on how thick your wood is. For example, many plastic laminate countertops are 5/8 inches thick but can still support a cast iron sink. Ideally, you want at least ¾ inches thick.

2. How do you secure a cast iron sink?

You won’t need clips. All you need is to caulk the lip of the sink to secure it to the countertop. Some plumbers recommend you have a support frame in case of any structural issues with the cabinet.

3. Do cast iron sinks need clips?

No, clips aren’t necessary. However, you will need to caulk under the lip before you set the sink. However, some might choose to place clamps until the silicone cures.

Final Thoughts

Cast iron sinks aren’t as hard as it looks to install. They do require quickness and carefulness with the installation though. You can install it with just caulk or putty, but it’s recommended you take the extra steps to add a support frame.

A cast iron sink does work with most kitchen countertops. It’s best to check how thick your cabinet is before you purchase a sink and complete measurements. Hopefully, this handy guide has taught you how to install a drop-in cast iron kitchen sink with ease for your next project.

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