Water is in abundance in any laundry room, so taming it and sending it in the right direction is critical. Since that water has nowhere to go, move it in the right direction: down a drainpipe and into the sewer main. A laundry room floor drain is the escape route for the water. Much as your shower drain collects water at a central point and sends it down and away, so too can a laundry room with a drain installed at the lowest point in the floor.
How Does a Laundry Room Floor Drain Work?
A drain in a laundry room provides a route out of the room for spilled water. Water on the laundry room floor moves to a 2-inch drain covered by a grate. The water flows vertically down a short initial section of ABS pipe below the floor, then through a P-trap, and out to the sewer main via branch drain lines within the house.
Most floors expect only minimal amounts of water. A laundry room with a drain behaves more like a waterproof basin.
Installing the laundry room floor drain ideally should be done as part of a flooring new-construction or full remodeling project. One reason is to provide full access to the structure below the flooring to run the pipes. Whether or not you build a new flooring system, the waste and vent runs will need to either run between the joists or the joists must be drilled to allow pipes to run perpendicular to them.
A completely waterproof floor sloped down to the drain must be built. Much like a shower pan, a sheet or liquid waterproof membrane should be placed under the floor covering (such as tile). The membrane should extend several inches up the walls and should be flashed to the drain collar, extending at least 24 inches from the collar.
If your laundry room floor slopes to a central point, that is the logical place to place the drain. If the floor is flat and level, you may choose to locate the drain in a certain spot with the expectation that later on, you will create a sloped floor.
You should also think about the area underneath the laundry room. Do you have easy access or do you need to create access? Most importantly, is there an existing drain pipe that you can tie your laundry room floor drain into?
Codes, Permits, and Regulations
Before You Begin
Before you begin this project, locate the eventual tie-in point where you intend to locate the sanitary tee. A sanitary tee is a plumbing fitting that connects a branch line (like the laundry room's drain) to the vertical drain that leads out of the house.
If the lower area is a habitable floor or a finished basement, you may need to remove a portion of its ceiling. Drop ceilings on suspended metal grids can be accessed by removing ceiling panels. If you have a drywall ceiling, you must cut into it, remove the relevant portion, and then re-install drywall after you have finished.
Equipment / Tools
- Reciprocating saw or hacksaw
- Speed Square
- Circular saw
- Cordless drill
- 6-foot ladder
- Laser level or bubble level
- Tape measure
- Carpenter's pencil
- 2-inch hole saw or jigsaw
- 2-inch ABS floor and shower drain
- 2-inch ABS hub-x-hub P-trap
- Glue for ABS and PVC pipes
- 2-inch ABS pipe, about 8 feet or as needed
- 2-inch ABS hub-x-hub coupling
- 2-inch ABS DWV hub-x-hub-x-hub tee
- Galvanized steel hanging strap
Locate and Cut a Hole in the Floor
With a 2-inch hole saw or jigsaw, cut a 2-inch hole in the laundry room floor at the intended drain location. If your laundry room floor already has tile flooring, you will also need to remove a small section of tile, mortar, and grout.
Be sure to locate the hole for the drain at the lowest point of the floor. If it is located at a high point, the floor will not properly drain.
Install the Drain in the Floor
Install the ABS floor and shower drain on the floor and screw it into place. The lower extension should completely fit through the hole and extend into the floor below.
Install an Extender Pipe to the Drain Assembly
Cut a 12-inch section of ABS pipe. Be sure to cut the pipe square. Remove plastic burrs with sandpaper. Smear ABS glue on the inside of one side of the ABS 2-inch coupling, then more ABS glue on the outside of the ABS pipe extending below your laundry floor. Set the two pipes together and firmly hold until the glue has set (about one minute).
Install the P-Trap
Determine a straight line extending from the drain pipe that is now in place to the house's drainage system, as the two will eventually connect. Couple the P-trap to the assembly that you created in the previous step, making sure it follows that straight line. Then, glue together the two sections of the P-trap, again making certain that it is pointed in a straight line to the eventual drain line.
Cut Into the End-Point Drainage Pipe
With a reciprocating saw or hacksaw, cut into the end-point drainage line. Assuming that this pipe is ABS, fit and glue the 2-inch sanitary tee into the cut section. Add steel hanging straps, screwing the straps on floor joists to carry the weight of the ABS pipe.
To meet plumbing code, the drain must also tie into an existing vent stack. Use a sanitary tee to connect into the vent stack. This tee must be above the floor rim of the fixture it serves.
Install the Pipe to the ABS Tee
The drain line must slope at a minimum of 1/4-inch for every horizontal foot. Cut the 1/2-inch ABS pipe so that it stretches from the P-trap to the ABS tee. When measuring, be sure to account for the inside of the hub of the couplings.
Tips for Installing a Laundry Room Floor Drain
- Installing water-resistant baseboards helps to protect walls in the event of large-scale water spills.
- With ABS/PVC glue, generously smear all surfaces of the pipe, but do not use so much that the glue drips.
- Fitting ABS pipes is easier with practice. Buy an extra 2-inch hub-x-hub ABS coupling and practice fitting it to short waste pieces of ABS pipe.
- ABS pipe tends to push out when it is glued into a coupling. Hold the two sides firmly in place until the glue cures.