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Michigan State University Extension
Home Maintenance And Repair - 01500169

Fixing Main Drain Plugged with Roots

Sometimes the main drain from the house may be plugged with roots, or the drain to the septic tank might be full; so first check to be sure other drains in the house are clear. If other drains are plugged and toilets don't flush, the problem is most likely in the main sewer outside the house. Temporary repairs can be made by using a plumber's tape, a 50' to 100' long strip of steel about 1" wide and 1/8" thick with a point on the end.

Find a cleanout plug in the basement near the outside wall where the drain goes out to the septic tank or street sewer. With a large wrench remove the brass plug and start the point of the tape down the drain. If the tape hits an obstacle, ram it back and forth until it clear. When it clears you will probably hear the water gurgle as the pipe empties. With a hose flush the drainpipe before replacing the plug.
(Vis. 1)use the cleanout and use a hose to flush

If the stoppage feels like roots, then water draining slow and the stoppage recurs frequently you might try copper sulfate to kill the roots. The following steps should be followed.

1. Where stoppage is serious and recurrent, apply 5% copper sulfate crystals, once a month until condition is much better. A drugstore or chemical supply store has this material.

2. Follow this with one pound doses per year (mark on your calendar).

3. Don't allow copper sulfate to stand in fixture traps, as metal corrosion may occur. Flush the crystals through toilet bowl or through the cleanout in the basement and follow with enough water to insure

(a) their transmission through the soil pipe to beyond the cellar wall and

(b) their conveyance to and against the root obstruction.

NOTE: The clean-out is not the drain where you dump laundry water. It is the place where a cap must be removed to gain entrance to the drain.

4. Don't expect immediate results from copper sulfate; only the life of the roots is taken by the copper treatment, and thereafter the normal processes of decay must ensue before roots can be carried on out to the main drain.

5. Don't expect the treatment to clean sewers mechanically obstructed by breakage, bad construction or foreign material.

When copper sulfate is used in connection with a septic tank tile field, the solution could be poured into an opening in the tile line beyond the tank itself. If you run the solution in the through the septic tank it will be diluted and not clear a stoppage in the tile field and might temporarily affect the bacterial action in the tank.


This article was written by Anne Field, Extension Specialist, Emeritus, with references from Michigan Extension bulletin First Aid for Plumbing.

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