Project Overview: Installing a new drain assembly is a crucial step in kitchen renovations or updates. This project typically takes 45 minutes to 2 hours to complete and is suitable for beginners with an estimated cost ranging from $15 to $30.
Working Time: 45 mins – 2 hrs
It connects to a sanitary tee fitting in the branch drain and should slope down toward the tee at about 1/4-inch per foot for proper drainage. Measure up from the floor or base of the cabinet to the center of the trap arm. If the height is more than 16 inches, you may find that a new sink will not allow for the necessary downward slope for the trap arm.
Lower the Drain Outlet, If Necessary. If you find that the existing drain outlet is not low enough to accommodate the depth of the new sink, you (or a professional) will need to open the wall and lower the position of the sanitary tee connecting to the drain pipe in the wall. This can be a somewhat complicated job that requires cutting away the back of the cabinet and the wall surface. Our example is a case in point—the new sink left insufficient room for connecting a standard drain assembly to the drain outlet in the wall (left photo). So, the sanitary tee fitting serving as the drain outlet has been lowered (right photo). Keep in mind that the drain height must leave enough room for removing the trap and cleaning it out. If you need to lower the sanitary tee in the branch drain, it is a good idea to wait until the other parts of the drain are test-fitted before gluing and securing the fittings permanently. Leaving the fittings loose will allow you some room for adjustment. Before continuing to the next steps, remove the old sink and install the new sink in the countertop. Our installation will include a double-basin sink with a garbage disposal fitted to the right basin. Install the Garbage Disposal and Strainer. First, install the garbage disposal onto the desired side of the sink, since this takes up the most space. Next, install a basket strainer onto the remaining sink basin. This is also a good time to install any other under-sink components, such as a water filter or a hot water dispenser. You will need to work around these fittings as you connect the drain pipes. Install the Drain Tailpiece and Continuous Waste Pipe. The drain tailpiece is a short vertical length of straight pipe that joins the sink strainer to a tee fitting. The side outlet on the tee fitting will accept the continuous waste pipe coming from the garbage disposal (or the other sink basin), while the bottom outlet will continue on to the drain trap. Temporarily install the tailpiece onto the sink strainer, using a slip nut (and slip washer, as applicable). Temporarily connect the curved end of the continuous waste pipe to the garbage disposal’s drain outlet, using a slip nut and washer. Let the straight end of the pipe extend past the vertical tailpiece on the sink basin. The pipe should slope downward slightly toward the tailpiece. Hold the tee fitting up to the tailpiece and waste pipe, and mark cutting lines on both pipes, where they will fit into the tee fitting. Now, cut the tailpiece and continuous waste pipe to length with a PVC tubing cutter or a hacksaw. Reinstall the tailpiece and continuous waste pipe, along with the tee, leaving the connections hand-tight.When installing a sink drain, it’s essential to adjust the pieces as necessary. Ensure that the continuous waste arm has a slight downward pitch toward the tee fitting. Tighten the slip nuts slightly more with channel-type pliers, but avoid overtightening to prevent damaging the plastic threads.
For single basin sinks, there’s no need for a tee fitting on the tailpiece; it will lead directly down to the drain trap. In contrast, double-basin sinks without garbage disposals will have a tee fitting installed on one basin’s tailpiece, with the side outlet accepting a continuous waste pipe from the second basin. Next, connect the drain trap, which consists of a U-shaped trap bend and a J-shaped trap arm. Assemble these loosely with a slip nut and washer. Slide a slip nut and washer onto the straight end of the trap arm and push the trap bend up into the tee fitting on the tailpiece while sliding the trap arm into the drain outlet at the wall. Adjust the trap pieces to create the most direct path from the sink to the drain outlet, ensuring the trap arm has a slight downward angle toward the drain outlet. If the trap arm is too long, mark and cut it as needed, then reinstall the P-trap assembly. Tighten all slip nuts with channel-type pliers, but avoid overtightening. Ensure that the continuous waste pipe and the trap arm slope slightly downward in the direction of water flow. Check all drain connections to make sure they are tight. Remember to face the trap correctly, with the sharp bend below the tailpiece. Finally, check for leaks by running water in both sink basins and tightening any leaking connections. If slip-nut joints leak slightly, fix them by unscrewing the nut, repositioning the washer, and re-tightening the nut, ensuring it’s not cross-threaded. Lastly, learn how to make dishwasher drain hose connections, which is a crucial part of sink drainage system setup.