How to Use Copper Sulfate to Kill Tree Roots

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Copper sulfate, also known as bluestone, is an inexpensive herbicide and algaecide with a variety of applications. Purchased in the form of small white or dyed blue crystals, this commonly found product can be used to clear potentially harmful algae out of ponds, lakes, and pools. But it is more often used to clear sewer lines of invasive tree roots, which can burst pipes and lead to costly repairs if left untreated. Copper sulfate is an effective root destroyer, and it's easy to apply to a sewer line. But out of consideration for the environment, it cannot be used in every situation.

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How to Use Copper Sulfate to Kill Tree Roots
Image Credit: Zen Rial/Moment/GettyImages

The Right Fit

Because copper sulfate can be toxic to animals and its buildup in aquatic environments can harm both plant and fish populations, the use of the root destroyer is banned in certain areas. As a result, before using copper sulfate as root killer, you'll need to check with local and state ordinances to see whether the treatment is legal or not. You will also need to determine if your sewer line has an issue that copper sulfate can fix: To check the state of the line, it's advisable to get a camera treatment done on your pipes, either by a licensed plumber or through your local government's office, which will sometimes do this for free. It should be noted that copper sulfate cannot solve major root infestations: If tree roots have greatly invaded your sewer line, it's likely that attempting a copper sulfide treatment will only poison the environment, and you'll still need to pursue other means of clearing – or in that situation, more likely replacing – the pipes.

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Copper Sulfate Root Treatment

If after inspection you've found that there is a manageable blockage of roots in the sewer line, copper sulfate can be used to treat the problem (once again, if the compound is legal to use in your area). To do so, pour half a cup of copper sulfate crystals into your toilet – but not your sink or shower, as the crystals will erode the pipes and cause leaks – and flush it down the drain. After 10 minutes, repeat the process once, then two to three more times without adding crystals to flush the copper sulfate down to the problem area. Once done, turn on any fans and open any windows present in the bathroom and rooms immediately connected to it, then leave your home for a few hours to avoid breathing in irritating fumes. Pets should also be removed from the home for that period, as copper sulfate fumes, while only irritating to humans, can be incredibly toxic to dogs, cats and other animals.

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Upon returning home, test the sewer line by flushing your toilet. If the single treatment worked perfectly, excellent. If it didn't, don't fret: It may take a few days for the dead roots to break off and clear the blockage.

Repeating Line Treatments

If after a week your copper sulfate root treatment has failed to clear the line blockage, repeat the treatment process once a day for a week. This should ensure any roots present in the line are killed and on their way out of your pipes. You may then flush half a cup of crystals once every six months to a year, as needed, to ensure that new roots do not invade the sewer line.

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Blake Flournoy is a writer, reporter, and researcher based out of Baltimore, MD. As a handyman's apprentice operating out of the Atlanta suburbs, they made a name for themselves repairing appliances and installing home decor. They have never seen Seinfeld and are deathly scared of wasps.