How to Clear a Clogged Main Drain Pipe

What You'll Need
Large bucket or plastic container
Large adjustable pipe wrench
Old rags, newspapers and cloths to absorb waste water
Old mop
Old clothes
Rubber gloves
Rubber boots
Small waterproof flashlight
Drain auger
Root cutting auger
Garden hose
Plumbers tape


When clogs persist although you have cleared sink and toilet drains, the main drain may be where a large clog has built up. Follow these directions to clear a clogged main drain from your house.

Step 1: Locate the Main Drain Clear Out in Your Basement

The main drain clear out is a Y-shaped, large pipe, either 3 or 4 inches across. It will be near the foundation of your house, near where the main wastewater drain goes through the foundation wall.

Step 2: Prepare the Clear-Out Area for Drain Cleaning

Wedge a large bucket or container under the Y-shaped clear out as tightly as possible. Spread plenty of old cloths, rags and newspapers on the floor around the container, to soak up the wastewater backed up in the clear out. Put on old clothes, rubber boots and rubber gloves to do this wet, messy task.

Step 3: Remove the Clear-Out Plug

Fit your adjustable wrench around the clear out plug on top of the Y-arm of the main drain. Turn it slowly anti-clockwise to release and remove it from the drain.

Step 4: Absorb the Wastewater Spillage

Catch as much of the wastewater spillage as you can in the container, and use the mop and sponges to gather up more. Keep mopping up the wastewater until the flow from the drain slows, then stops.

Step 5: Use the Drain Auger to Clear the Blockage

Check with the waterproof flashlight to see if you can spot the blockage in the main drain. Insert the drain auger as deep as possible into the drain and turn its handle to grind through the clog.

Step 6: Reinstall the Clear-Out Plug

Once you are sure you have cleared the clog in the main drain, reinstall the clear-out plug and test the drain by running some water into a sink, toilet or other fixture. If there is still blockage in the main drain, you will need to look outside for the source of the clog.

Step 7: Remove Roots from the Main Drain

Outside in your yard, a tree may have managed to grow roots into the main drain line, through the pipe joints. Rent a root cutting auger from a building supply center for the day. Open the clear-out plug inside the house. Go outside and excavate a section of the drain closest to the tree roots that are causing the problem. Insert the auger cable of the root cutting auger into the drain at the clear-out Y, and activate it. You will feel higher tension in the auger cable as it cuts through the roots. Remove the auger once its tension slackens off. Flush the drain with water from a garden hose to clear out the segments of tree root in the drain. Cut away external tree roots and seal off the drain with plumbers tape. Flush toilets in the house several times to check the blockage has been cleared.