Building the Better Slot Drain

Like most great ideas, this one came to me shortly after a horrible failure. It was born out of necessity for a better slot drain system; a system that would be easy to fabricate and that would be loved by clients and plumbers alike. We all fear failure to a certain extent, but some breakthroughs depend on it.

It was a normal Tuesday afternoon in the studio and we were preparing for a local tradeshow. I clearly remember two of my employees carrying a vanity top with an integral concrete sink to be loaded into the truck. This particular sink was a type of wave sink with a slot drain running along the back. The system we were using at the time for plumbing our concrete sinks required a long tail piece sticking out of the bottom of the sink. I watched as they carried the piece over a cart and caught the end of the tailpiece coming down, resulting in a huge kink in the tailpiece rendering the sink useless in an instant. Employees hit the deck, tools flew, words were spoken and a great idea was conceived.

There are two main plumbing configurations currently available for concrete sinks with slot drains. One was described in the above horror story. The second is the pan method in which a stainless steel metal pan (which costs around $100) is screwed and caulked to the bottom of the slot. The main problem with the pan method is that it provides the perfect breeding ground for mold (dark and moist environment), which in turn poses a serious health risk for the client, and more importantly a major liability for the fabricator. I am writing this tutorial so that a small portion of our craft can be improved upon as a whole. This system has been tried and proven for many years now and I believe it is better than any other technique or product available to our industry today.

We are going to take you step by step through the Elements integral drain method where 12 dollars of hardware and 15 minutes can get you a drain configuration that’s easy to transport and a monkey could plumb. Let’s get started.

step 1

Step 1 – Gather the necessary tools and supplies. You will need a grid drain,, 2” blue foam, 5- minute epoxy, a 2 ½” screw, a large fender washer, duct tape, 100% silicone caulk, a sanding block, a screw gun, and an angle grinder with a metal cut-off blade,; most of which you should find kicking around the shop. We purchase grid drains by the case from a local plumbing supply for about $12.00 each, but another option is where they can be purchased for $11.95 each through their free catalog.

Step 2 – Remove the threaded tail piece and mark 3/4” from the female threaded portion of the drain.

step 2

Step 3 – Cut the female threaded portion of the drain at the mark and discard the portion with the grid top. You can also discard any other remaining parts that came with the drain setup that are not shown in this picture. We are now left with a 3/4” section of pipe with female threads, a large nut, and a male threaded tail piece. I typically keep the tail piece in its the original box with the client’s name on it.

step 3

Step 4 – Apply some 5- minute epoxy to the threads of the nut and screw the nut onto the section of the pipe that was cut off the drain. Be sure the nut is over the female threaded section of the pipe as shown in the photo. It is also a good idea to apply a bit of wax to female threads before using the epoxy in case of any drips. Leave the nut 1/16” higher than the female threads so that when you grind the excess concrete off of the drain you hit the nut before you hit the female threads. Think of the nut as a force-field from the grinding wheel.

step 4

Step 5 – Cut a foam plug from the blue foam that will fit snugly into the piece just removed from theyou just cut off the grid drain, and shapinge the end into a wedge with using a sanding block. The tip of the wedge should stick out of the side with no female threads; the side with the female threads and the epoxied nut should remain flush. Apply a bead of silicone caulk to fill any gaps and to ensure that concrete will not work its way into the drain.

step 5

Step 6 – Attach the slot to your sink mold as you normally would. We make our slots from ½” PVC sheets and the slot should be tapered ¼” per foot towards the drain. In this example we are placing the drain in the middle, so the slot is tapered from each end into the middle. Be sure to leave the center 1” section flat for mounting of the drain assembly. It is also important to pre- drill a pilot hole in the slot so the drain assembly screws in straight.

step 6

Step 7 – Fasten the drain to the slot using the 2 ½” screw and 1 ½” fender washer; tighten the screw enough to compress the foam onto the PVC for a tight fit. Notice the fender washer is large enough to rest on the metal part of the assembly, not just the foam. Be sure to level the drain with the mold so the tail piece is perpendicular to the sink and not skewed. Another added benefit of using ½” PVC sheets for the slot drain is that they it allows for easy cleaning and a wide enough base to screw the drain assembly into. Use the duct tape to cover the screw head and threads so that concrete does not creep into the drain threads or the head of the screw.

step 7

step 7

Step 8 – For GFRC users, simply spray and hand pack around the drain, be sure to pack a little high so that you can grind down flush to the nut. For wet cast users, simply pour flush with the top of the drain. After grinding, simply remove the foam plug with a wooden shim or ppopsicle stick to ensure that the threads will not be damaged. The bottom of theis particular sink shown required a small step to accommodate the cabinetry which is not typical.

step 8

Step 9 – Provide your client with the tailpiece so the plumber can cut it to size and simply screw the threaded tailpiece into your new female threaded drain assembly. It’s sure to impress!

step 9

Step 10 – Enjoy your new Elements integral drain method without the worry of a cumbersome tailpiece hanging off your sink or the fear of mold growing in your pan.

step 10

Elements Concrete also offers a rubber plug for the drain assembly to replace the foam plug and it is reusable for hundreds of uses with proper care. If you are interested in purchasing a rubber plug visit us online at you can find purchasing information in the “news” section of our website. We also welcome all questions, comments, criticisms, or improvements to any of our ideas and techniques. Please send all correspondence to so I can personally address any inquiries.


Elements Concrete

Jerrad Inlow
Tagged As:
PROUD SPONSORS   Learn about advertising with the Cartel