How To Install a Drop-in Cast-Iron Kitchen Sink

Cast-iron drop-in sinks are durable, beautiful, and timeless. Best of all, they’re normally easy to install – but you’ll definitely need more than one person to lift the sink into place. 

If you want to know how to install a cast iron sink, good news! Cast iron sinks are easy to install just like any other sink. You have to cut a hole, place the sink, and fasten it to the plumbing. However, cast iron sinks also need extra support. 

Before You Begin the Installation Process 

Cast iron sinks are heavy. Chances are, your kitchen countertop can’t support the weight. In fact, American Standard, one of the largest manufacturers of cast iron sinks in the USA, says they weigh up to 350 lbs. when full of water. 

Bracing a Cast Iron Sink 

Most installers handle the weight of a cast iron sink by simply hanging it on the wall. This means using a free-standing countertop with the back removed or running the braces through the wall. Braces are available at most stores that sell cast iron sinks. In addition, you can choose to build a frame or use braces to support the side instead. Bracing a cast iron sink is also known as “Anchoring” it to the wall. 

If you’re not building a very sturdy frame with at least 2”x4” under your cast iron sink, you need wall anchors. 

Tools Required 

Installing a drop-in sink is a relatively simple process. However, you’ll definitely need tools. 

  • A level 
  • A drill 
  • A spade bit (at least 11/4” but hopefully 2” 
  • A jigsaw or circular saw (ideally both)
  • A level 
  • A measuring tape 
  • Sink braces or wall anchors/hooks
  • A drill 
  • Hacksaw 
  • Pipe glue 
  • PTFE Tape 
  • 2” ABS pipe 
  • P-Trap 
  • 2+ 90-degree ABS 2” elbows 
  • Pipe Y’s and/or sanitary tee’s as necessary 
  • Adjustable wrench 

You’ll also need someone to help you lift the sink into place. And, unlike when you use a steel sink, cast iron sinks don’t have to be clipped to the counter. However, you may still prefer to do so. 

Installing a Cast Iron Drop-in Sink in 5 Easy Steps 

No sink is complicated to install. But, some steps of the process can be finicky. And, if you’re planning to do the plumbing, you might have to check with local regulation first. 

Measuring the hole

The hole for your sink should be as small as possible to fit the sink in, without allowing it to slide through. Why? The more support on the lip of the drop-in sink, the sturdier it will be. That’s less of an issue if you’re using wall braces to keep a significant portion of the weight off the countertop. However, it’s likely still an issue. 

  • Measure the lip of the sink from the underside. To speed things up, place the sink upside down on the countertop and trace the outside of the sink. Measure the distance between the outside of the lip and the inner lip. Trace a hole that distance inside the hole you’ve traced around the sink. So, if your sink is 30” x 32” and the lip inside is 28” x 31” you know that you have 2” on two sides and 1” on two sides, and you’d narrow the existing hole by that much. 
  • Make sure your hole is squared and levelled to the sides of the countertop. Both front corners should be the exact same distance from the front of the counter. 
  • Make sure the sink placement on the countertop allows you to support it with anchors or a frame inside the counter 
  • Use chalk to trace lines. Once you’re sure of the lines, use a marker because chalk rubs off of countertop surfaces very easily. 
  • It’s important to align the sink with wall studs or to install a brace in the wall to support the sink anchors. 

Cutting the hole 

If you have stone, quartz, or granite countertops, you always want to have a professional cut them. This also holds true if you have a glass countertop. In addition, if you have a laminate countertop, you want to place cuts from the top. Otherwise, your laminate may chip outward, leaving large chips around the edge of your sink. 

In most cases, your best option is to use a skill saw or a rotary saw to cut the long straight lines around your sink. If you have a curved surface, you may want to use a jigsaw instead. Here, use a spade bit to cut a circular hole near the edge where you want to begin cutting. Use the hole to insert the blade. Plus, you always want to double-check that your bits are suitable for the material you’re cutting. Finer-toothed wood blades are almost always better for laminate because they are less likely to cause chips. Make sure you go slowly at corners and don’t overshoot your corners. Chances are, you want to drill a hole per side of your sink, so you can more easily approach and cut corners. 

In addition, you always want to ensure you cut wood, laminate, or composite in a ventilated space, with safety glasses and a face mask rated for wood particulate. This is important because wood and sawdust can cause damage to the lungs. 

Installing braces

Most cast iron sinks need extra support, or they will eventually cause sagging or even countertop collapse. Here, your options are to build a support frame or to anchor your cast iron kitchen sink to the wall. 

If you want to install a frame, you’ll have to figure out how based on your cabinet, its structure, and its frame. However, you should use heavy duty wood and follow the lines of the cabinet to avoid using too much storage space for the frame. 

Installing sink braces is also relatively easy. 

  1. Make sure you choose braces or hooks designed for your sink. Most cast iron sinks have hooks or fittings in the back. Look for options from the same manufacturer for the best results 
  2. Drop your sink into the kitchen counter with supports underneath or a friend or two to hold some of the weight off the counter. Mark where the anchors need to be in the wall on the studs or on the brace you’ve installed for this purpose. Dropping the sink in first means you can align the holes directly with the hooks on the bank of the sink. 
  3. Remove the sink 
  4. Align the hooks and follow the mount instructions on the package. For wall hooks, that will likely be “Drill a hole and screw the hooks into place”. For cast iron clip hooks, you’ll align the center of the hook with the marked spot and use a drill to put two screws in on either side of each anchor. 
  5. Have a friend help you to lift the sink and hang it onto the wall hooks. In most cases, this means lowering the back end of the sink into the counter first, catching the hooks in the hook slots, and then slowly lowering the front. 

That’s it, your drop-in cast iron sink is in your counter. You may choose to install counter clips as well. However, most cast-iron sinks are so heavy they don’t need them. 

Connecting the plumbing 

It’s important to check if you are allowed to do your own plumbing in your region. Many areas specifically limit plumbing to licensed practitioners. It may be illegal to install your sink plumbing. If not, proceed with the following steps. 

Importantly, this to-do assumes that the foundations of your sink plumbing are already in place. This means that the P-trap is in place, the sink vent pipe is in place, and the sink drain is attached to the sewer. If not, you will want to look up these steps separately. This guide also assumes that your cast iron sink includes a 1 ½” tailpiece – which most stainless-steel sinks have. If not, you’ll have to install a trap and a tailpiece yourself. 

  1. Attach a 1 ½’ trap adapter to the sink tailpiece. In most cases, you can glue this in place. If you have a double sink, repeat for both drains. 
  2. Attach a 2” 1 ½” ABS pipe to the trap adaptor 
  3. If you have a double sink, you want to connect the sinks here. Use a 90-degree elbow for one or both sinks depending on where you need the drain to end. Connect the pieces using a straight section of pipe. Then use a Y or a sanitary tee depending on how you want to connect the pipes. 
  4. Add another section of pipe to drop the pipe to a desired height 
  5. Install the P-trap 
  6. Install a 90-degree elbow from the P-trap and run pipe to the drain
  7. If your sink vent is not already installed, install one now. 

In most cases, these pipes should not be glued together. Make sure they are watertight and go from there. 

You’ll also have to connect the hot and cold water the faucets. However, this is a simple matter of making sure your water mains are turned off, attaching the appropriate pipes to flexible hose, and running that up to the faucet. You’ll want to use PTFE or thread seal tape to seal the connections to make them watertight. Use an adjustable wrench to tighten everything in place. Most faucets also clamp down with a Philips or flat-head screwdriver, but this is highly dependent on the faucet itself. 

Checking the water connections 

Always be sure to test water connections and drainage to ensure there are no leaks. Run hot and cold water. You’ll also want to let water sit in the sink for at least half an hour to ensure the trap does not leak. Then, if it drains correctly, your cast iron sink is fully installed. 

Do Cast Iron Sinks Need Extra Support? 

In most cases, yes. Cast iron is incredibly heavy. That only gets worse when you fill your sink full of water, food, or pots and pans. Most countertops won’t be able to support a fully loaded cast iron sink on their own. Therefore, you almost always want to invest in sink anchors. 

Luckily, sink anchors are normally a few dollars at most. In many cases, they’ll even come free with your sink. The caveat is that you’ll have to put holes in the back of your cabinet and possibly install a brace to your wall studs. The good news, you probably already have holes in the back of your cabinet for the drainage. So, installing sink anchors takes a few minutes of extra time and ensures the longevity of your sink and countertop. 

Related Questions 

If you still have questions about your cast iron sink, these frequently asked questions might help. 

Why are cast iron sinks so expensive? 

Cast iron is expensive. Manufactures pay an average of 60 cents per lb. for raw fast iron. That’s before shaping, molding, or ceramic come into play. And, cast iron sinks often weigh upwards of 150 pounds each. In addition, cast iron and farmhouse sinks are something of specialty items. Most people don’t have them. If you’ve chosen to have one, you’re going outside of the norm of stainless steel for something that suits your home. You almost always pay more for products that are in lower demand because the manufacturer profits less by making less of them. 

Do cast iron sinks need clips? 

Cast iron sinks do not normally need clips. In most cases, they are heavy enough to create a seal with the countertop without. However, you may choose to install clips. On the other hand, that depends on if you can find clips that are thick enough to actually seal with a cast iron sink. 

How much does a cast iron sink weight? 

Cast iron sinks weigh anywhere from 100-350+ pound. That difference depends on the sink’s size, the thickness of the ceramic coating, and the manufacturer. Older sinks are almost always heavier. Plus, if you have a double cast iron sink, you can expect it to weigh a great deal. 

Next Steps

Cast iron or farmhouse sinks are beautiful, sturdy, and timeless. On the other hand, installing them can be a hassle – especially if you have to install wall braces. Plus, you’ll almost always need help lifting your sinks into place. Even if you’re quite strong, it’s better to wait for help than to risk damaging your sink. Good luck with the installation.

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