Install A KERDI Horizontal Floor Drain in a Shower

April 13, 2018


When shower waste lines take a hard turn, use a floor drain that turns with it

Schluter®-KERDI-DRAIN-H is a floor drain with an integrated bonding flange and a horizontal outlet.  It is ideal for applications where a waste line runs into a wall or where the direct connection of the drain to waste line in the floor is not possible or practical.

In this way, KERDI-DRAIN-H can be positioned as desired without relocating the plumbing.

This feature is particularly beneficial for applications over basement slabs, suspended, or post-tension concrete floors or wood floor installations where relocating the hole in the floor is not practical.

The flange is available in both ABS and PVC with a 2” (two inch) outlet.

Schluter®-KERDI-SHOWER-CB is a compensation board that is used to raise the elevation of the KERDI-SHOWER (trays to account for the height of the horizontal waste line.

Let’s get started.

We are demonstrating an installation over a concrete subfloor where we were unable to relocate the waste line as desired. Measure the shower area to determine the placement of the drain and waste line.

Place the KERDI-BOARD-CB compensation board on the subfloor. The compensation board can be easily cut to fit the shower dimensions using one or more boards.  

  • Dry fit the shower tray. Mark the board where the drain flange will be. The flange location is marked using the included template. Measure and mark the drain location.
  • Next, we mark the location of the slot for the waste line. A standard 2″ waste line requires a 2-3/4 inch wide slot in the compensation board. The maximum allowable spacing for this slot is 3 in.
  • We made all our cuts in the compensation board using a jigsaw. Replace the compensation board and ensure proper fit before beginning the installation.
  • The substrate must be clean, even, and load-bearing. Any leveling of the subfloor must be done before the installation of the compensation board.
  • KERDI-SHOWER-CB is installed using any of our Schluter® Thin-set mortars or an unmodified thin-set mortar.
  • A 1/4 inch x 3/8 inch square or U-notched trowel is used to apply the mortar. Apply a thin layer of mortar to the subfloor with the flat side of the trowel to produce solid contact with the surface and then comb additional mortar using the notched side of the trowel.
  • Set the compensation board into place and solidly embed in the mortar. We used a piece of cardboard to protect the compensation board while embedding.
  • Plumbing must be prepared according to the codes effective in your region.
  • Use the spacers found in the flange packaging to ensure that the drain will be positioned at the correct elevation. There are two sets of spacers included. Make sure to select the spacers that correspond with the shower tray you will be using.
  • KERDI-DRAIN-H can be connected to the waste line before installation of the shower tray.

Alternatively, the plumbing can be connected before installation of the compensation board

  • Measure and cut a section of pipe to connect KERDI-DRAIN-H to the odor trap and dry fit the plumbing components.
  • Use the detachable center section of the tray or the foam spacers included with the drain as a spacer. Proper slope MUST be maintained to ensure adequate drainage.  
  • Next, prepare the KERDI-DRAIN-H and the pipe with cleaner, primer, and ABS or PVC cement per the solvent cement manufacturer’s instructions and connect the flange.

Now that the plumbing connections have been made, we’ll install the KERDI-SHOWER tray

Before installing the shower tray, fill the slot in the compensation board with mortar, such as dry pack or sand mix, to support the tile assembly if ANY of the following conditions are present.

  • The shower tray will be exposed to heavy loads.
  • The shower tray seam will be located over the slot cut in the compensation board for the waste line.
  • Mosaic tiles smaller than 2 inches by 2 inches will be installed.

Since none of these conditions are present in our installation, we can continue with the shower tray installation.

  • Remove the center section of the KERDI-SHOWER tray and the spacers from the drain flange.
  • Apply thin-set mortar under the drain flange and to the compensation board where the center sections of the tray will be installed.
  • Then apply it to the top and bottom of the detached center section of the shower tray as well.
  • Slide the center section into place under the KERDI DRAIN-H to ensure solid and uniform support of the bonding flange.
  • Check the drain for level. Clean away excess mortar.
  • Finally, the KERDI-SHOWER tray is installed over the compensation board.
  • Apply a thin layer of mortar to the compensation board and then comb additional mortar using the notched side of a ¼” x 3/8” inch trowel.
  • Solidly embed the KERDI-SHOWER tray into the thin-set mortar. We used a piece of cardboard to protect the tray while embedding.

Next, we will make the waterproofing connections, starting with the KERDI collar application.

A 1/4 inch x 3/16 inch V-notched trowel or the Schluter-KERDI-TROWEL, which features a 1/8 inch x 1/8 inch square-notched design, is used to apply the mortar.

KERDI waterproofing accessories are installed using any of our Schluter Thin-set mortars….or an unmodified thin-set mortar. The mortar is mixed to a somewhat fluid consistency, but still able to hold a notch.

  • Apply a thin layer of the mortar with the flat side of the trowel to produce solid contact with the surface and then comb additional mortar using the notched side of the trowel.
  • Center the KERDI collar over the KERDI-DRAIN and embed using the flat side of the trowel or a drywall taping knife. Make sure this connection is secure.
  • The KERDI-BOARD-SC shower curbs are installed in the same manner as the tray. Make sure the mortar is applied to all points of contact with the curb, including the subfloor, walls, and edges of the compensation board and shower tray for proper support.
  • Solidly embed the curbs.  
  • Using the same technique as shown with the KERDI collar, install the KERDI-KERECK corners and KERDI-BAND waterproofing strips to seal the shower tray to the walls and curbs.
  • Make sure you have two-inch overlaps at all seams.

The installation of the KERDI-DRAIN-H and KERDI-SHOWER-CB is now complete. Schluter®-KERDI-DRAIN-H integrates with the Schluter®-Shower System and is the perfect solution for horizontal drainage.


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