How to Unclog a Basement Floor Drain

In many homes, all the drain pipes from your house and garage lead to your basement floor drain. A buildup of laundry lint, soap scum, garbage disposal debris and grit from snow-covered cars eventually can cause a blockage in the main floor drain. Instead of calling a plumber, you can save time and money by renting an electric power auger and unclogging the drain yourself. However, power augers can cause serious injury or damage to equipment if mishandled, so follow strict safety measures during use.

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Practice safety when cleaning your basement floor drain with a power auger.

Equipment and Preparation

Rent an electric power auger with at least 50 feet of cable and a ground fault circuit interrupter. If the cord is too short, use a heavy-duty three-wire extension cord. Press the "test" button on the interrupter and then press the "reset" button before each use; the red light on the interrupter will come on if the circuit is operating properly.

Examine the power cord and ensure that it has no cuts or frays. Make sure that the cord has a three-point grounding plug, and connect the machine to a three-point grounded wall socket. Before plugging it in, clear out any standing water in the basement with a bucket and dry the floor with a mop.

Position the machine within two feet of the drain opening to prevent excess cable from whipping back and forth when the auger runs at full speed . If this is not possible, feed the auger through a length of 3/4-inch metal pipe laid between the machine and the opening.

Drain Access

Undo the two retaining screws and remove the round grate cover from the drain hole. Locate the clean-out plug on the side of the drain basin and squirt a liberal amount of penetrating oil on the plug's outer rim. Allow about 15 minutes for the oil to penetrate into the threads.

Fit the jaws of a large monkey wrench over the square lug in the center of the clean-out plug from the bottom, with the wrench jaws facing upward and the handle pointing toward the right. Grasp the wrench handle and apply upward force to loosen the treads by cranking the wrench counterclockwise. Once loosened, spin the plug off the threads and lay it aside; this will allow you to bypass the U-shaped trap in the bottom of the basin opening by inserting the auger directly into the drain through the clean-out plug opening. Proceed as described below.

If there is no clean-out plug, you must remove the back flow preventer from the trap inlet in the bottom of the well and then push the rotating auger through the trap. Apply penetrating oil around the outside edge of the preventer retaining ring. Let it stand for 15 minutes and then loosen the ring by placing the tip of a cold chisel against the left edge of one of the square notches on the rim and delivering two or three heavy hammer blows to the chisel. Once the ring comes free, spin it off counterclockwise, remove the ball float and lay the parts aside for later reassembly.

Penetrating the Blockage

Install the small spear head onto the end of the cable and lock it firmly in place by tightening the retaining screw in the side of the fitting.

Set the machine for clockwise rotation and feed the auger cable into the drain until it meets the first obstruction. Pull one or two feet of extra cable out of the machine's cable cage, so that the loose cable forms a loop above the opening. Tighten the locking thumb-screw on the cable cage head to lock the cable in place. Grip the cable with both hands and turn the machine on by pressing down on the foot switch.

Feed the looped loose cable all the way into the drain by hand. If the motor slows and starts to bog down, stop the machine immediately and set it for counterclockwise rotation. Loosen the thumb-screw, turn the machine on and back the cable out a foot or so until it runs freely. Switch back to clockwise rotation and push the cable into the drain until it rests against the obstruction. Apply moderate inward force until the auger clears the obstruction. Continue until the spear head penetrates any further blockages downstream. Repeat the reverse procedure whenever the auger encounters heavy resistance that causes the safety drive clutch on the machine to start slipping.


Replace the spear head with the largest circular cutting head supplied with the power auger. Turn on the machine and insert the auger all the way in to scrape the walls of the pipe. Once you fully extend the augur, leave the machine on and pour several buckets of hot water down the drain while slowly pulling out the auger. This will wash away any loose debris while cleaning the auger and cutting head.

Wrap three or four tight spirals of Teflon tape clockwise around the thread of a new clean-out plug. Thread in the plug and tighten it firmly with the monkey wrench to prevent sewer gases from backing up into the basement. Replace the drain grate cover to complete the project.


Wear safety glasses to prevent eye injury from flying debris and heavy-duty leather gloves while handling the auger cable. Wear tight-fitting clothing and remove all loose jewelry, such as neck chains and bracelets, to eliminates the possibility that they will snag on the equipment.

Never force the auger cable. Stop the machine immediately if the cable slows and the machine starts laboring. Use the reversing procedure described earlier and turn the machine off and on repeatedly while withdrawing the cable. If you don't do this, torque will build up and the auger will start to buckle and twist itself into a series of crushing loops that could cause serious injury if your hand gets caught in one.

Maintain control by holding the auger cable with both hands and operating the machine's foot pedal yourself. Never allow a helper to control the foot switch.

Ian Kelly

After graduating from the University of the Witwatersrand and qualifying as an aircraft engineer, Ian Kelly joined a Kitchen remodeling company and qualified as a Certified Kitchen Designer (CKD). Kelly then established an organization specializing in home improvement, including repair and maintenance of household appliances, garden equipment and lawn mowers.