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topic 22201 p2

Killing roots with copper sulphate. What happens in drain/sewer pipe?

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A discussion started in 2003 but continuing through 2019

January 27, 2011

Q. My pipes go to a street sewer. How can I "hold in place" the Copper Sulphate to kill the tree Roots that are entering in the drain pipes? I just had Roto Rooter grind out the roots, as they did 3 years ago. Also, should the Copper Sulphate be washed into a sink or flushed in the toilet? and how much? Then would letting it sit overnight for many hours do the job?

Bill Spencer
- Sonoma, California USA

February 1, 2011

A. Just had Mr Rooter channel the main line through two blockages. They also installed a cleanout between the tank and the main line. Have a 30+ year old system. My question concerns copper sulfate and clay pipe. Does the copper sulfate harm clay pipes? The installer explained about copper sulfate and we did pour some in the cleanout and flushed with water.

Terri Martin
- Bulverde Texas USA

Sulfuric Acid
Drain Cleaner

February 27, 2011

A. I have a house built in 1941. It has clay pipes with roots in them. For years we used plumbers' Drano, nearly all the other things mentioned here. about 3 years ago the toilet was backing up into the tub. we plunged used Drano etc. we are seniors and have limited money. We were in Publix grocery store and debating whether or not to call the plumber. I saw a product I'd never seen before. The name is Liquid Lightening. it is virgin sulphuric acid. We used it and it worked. We have not used any other product since. It is about $10 for 32 ounces. It does not say it dissolves roots but anything organic. It has always worked for us.

alan jones
- jacksonville florida united states of america

February 28, 2011

! Hi, Alan.

Thanks for the success story. Be really careful with sulfuric acid -- it dissolves metal pipes as well as other stuff. And never even think about mixing it with any other drain cleaner. Most of the others are strong alkalines, and mixing a strong acid with a strong alkaline is explosively dangerous.


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

June 27, 2011

! I just wanted to warn people that if they use Copper Sulfate in their drain field there is a chance that they could kill any trees that are close to the drain field.
I found this out the hard way. My sewer repair person recommended I put 5 pounds of copper sulfate in my drain field once or twice per month after he cleaned the roots out. After one application I now have a giant live oak that is completely dead. Another huge live oak that is looking very unhealthy and a smaller live oak that is showing signs of being sick.
I only gave my sewer system one application because before it was time for the second application my trees were starting to drop leaves and look sick.
Had my sewer repair person warned me that this may happen I would have opted to have the drain field mechanically cleared of roots whenever it needed it rather than have my beautiful oaks killed.

Gary Keenan
retired - Lakeland, Florida, USA

June 27, 2011

Hi, Gary. Thanks for the warning.

However, you might want to talk to your county agricultural extension service and see if someone can confirm this as the cause of the death of your trees. Some knowledgeable horticulturists and floriculturists are quoted in the previously referenced page at
as saying: "Use of this treatment has yet to cause the loss of a tree or shrub".


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

September 4, 2011

As a Chemical Engineer the Copper Sulphate can corrode Iron pipes too fast:
CuSO4.5H2O + Fe = FeSo4 + Cu
The pipe will be washed up by water as FeSo4 ...

Jim Brown
- Milwaukee, Wisconsin, USA

Root Killer

March 5, 2012

I just purchased this product yesterday:

Roebic K-77 =>

The label indicates that it contains 99% copper sulphate and 1% inert ingredients. 2 pounds cost me $18 US. The instructions were to flush the product down the toilet at night before retiring. I hope it works.

Gary Harris
- Santa Fe, New Mexico USA

June 18, 2012

A. I would really question dumping large quantities of copper sulphate down the sewer. It is highly lethal..!! I would strongly advise checking with local authorities before doing it. This stuff can't be removed during the normal process of treating waste water. It could end up back in your drinking water.
Also...putting it in your septic system is just going to kill all the natural organisms and bacteria that have to be there for the septic system to work properly.
Really do your homework on this stuff before you use it.

Dave Little
- Whitby, Ontario, Canada

June 27, 2012

Q. In a post dated July 14 2009 by M A Tullos- Carson City, Nevada an answer was given that copper sulfate will not be effective 30-40 feet out.
My question is: if one flows an large amount of water when applying the CuSO4 will it not be carried to the root site and do an adequate job?
I have a problem with roots approximately 60 feet out, I would appreciate a response and would like to know that this treatment will work.

Tom Peck
- Linton, North Dakota, USA

October 8, 2014



October 2014

A. Hi Dot. It's available on-line everywhere, but you will surely find it locally in a pond store or garden store.


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

April 17, 2015

Q. My neighbour's maple tree has roots above ground on my lawn. When mowing my lawn it is harming my lawn mower. How do I get rid of these roots?

Gerry S [last name deleted for privacy by Editor]
- Fort Erie, ON. Canada

August 2, 2016

A. Problems with drain fields can be taken care for minimum cost. I use copper sulfate down my leech field once a year. I dig up my drain field at the end of my septic (I never put copper sulfate down my septic). I will open up the drain field and pour half pound down the opening of each outpouring drain and flush with water. Prior to that I will run my hose or long snake down the leech field piping and determine how stopped up it is. I will then take my pressure washer hose without the wand and run it down and blowing all the trash inside away. You may take a light snake and run down the drain to pull out any trash of feeder roots that may have built up in the drain. Then I will flush my copper sulfate down each drain. Takes a a couple hours once a year for this treatment. Trees all around my tank and leech fields. Has never harmed my trees and keeps my drain field flowing. I will do this tomorrow as has been year or so since my last treatment. Good luck.

alan crofoot
- old town, florida usa

September 24, 2016

I am replying to the person who used "5 pounds of copper sulfate" in the drain/line all at once, and a tree died after that treatment. All of my research indicates that five pounds of this noxious chemical is far too much to use; in fact it appears to be about 24 times the recommended dosage. The treatment advice I follow is: "Pour 1/2 cup of crystals into your toilet and repeatedly flush it until all they (sic) are gone. It is better to space the small treatments over a two-week period than to give the roots a single large dose on one day...After you flush copper sulfate down your toilet, leave your house for a day to avoid inhaling any of its fumes."

Barbara Bowden
- Russellville, Arkansas, United States of America

Root Killer

October 29, 2016

Q. I have roots in my downstairs shower. It clogs the shower and toilets and makes it overflow. Can I pour Roebic Foaming Root Killer down my shower drain?

James Klein
- reseda, ca, usa

November 13, 2016

A. Consider other mechanical or low tech solutions rather than copper sulfate. For those of us living near Lake Erie, 2012 had a serious algae bloom and fish kill attributed to agricultural chemicals. Ask yourself if you want to drink this? Lake Erie is our fresh water source.
Read before you make this choice,

Karin Lepp
- Niagara Falls, Canada

November 2016

thumbs up signThanks Karin. The abstract of that second article sounds great!

The world still desperately needs public libraries because you can't get authoritative research without someone paying for it, whereas we also can't really expect members of the public to pay $38 for an article :-)

(Yes, I realize that limited access can be gotten for less than $38, but I'm not talking about the exact licensing terms for one specific article, but rather the general problem of access to authoritative info being costly).


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Striving to live Aloha

April 16, 2017

Q. Hello,

I use mix of water around 90%,copper sulfate pentahydrate - 5% and 35% Sulfuric Acid - 2%. Whole amount of liquid is 20 Oz.
Is it safe to throw it in the drain? Do I hurt pipes, since Im using it to achieve a thin layer of copper on steel? Is it safe for bath tub, and can I paint the steel in bathroom, since I have to water rinse?
Thank you

Z Varga
Metal finishing - Subotica, Serbia

April 2017

Hi Z. In some countries, including the USA, the toxicity of a waste product is only half of the question; the other half is what was the source -- because the laws governing the disposal of waste depend on the source as well as the contents.

From the technical side, though, what you wish to dump is rather dilute, and very close to what is used to kill roots in drain pipes, and the quantity is not a lot -- so it's probably not a big deal to pour it down the toilet (it might stain the bathtub). But a better plan might be to stuff steel wool into your bottle, so the copper will plate out as metal, rather than remain dissolved.

Good luck.


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Striving to live Aloha

July 14, 2017

Above link claims that rock salt can be used as well as copper sulfate to kill roots in drain lines. I, myself, have no experience in using chemicals to clear drain lines. Therefore, I cannot comment on the efficacy of these methods. But certainly the rock salt is cheaper and more easily obtained than copper sulfate, albeit still hazardous.

David Biddle
- Cary, North Carolina, USA

December 27, 2017

A. Hello Metal Finishers, My fiance' & I just had our lateral roto-sliced for the first time by a professional for exactly $100, complete. (Not bad, huh?) In the past 6 years, we've rented 3/4 inch-diameter power snakes from (local home supply chain) for $75-(now)$85/day and done it ourselves.

The rental machines do not come with the slicing-type head; standard issue is: one spear, one curly-spring, and one U-shaped 2-inch-wide, chewed-up thing. The method has been to "snag" the clog, and RIP IT OUT by brute force, risking collapsing the clay lateral. This time, I found a plumber who had a single, curved, off-set-blade head, so we hired him. I could see the snake lash-back when he hit the root ball, but it sheared through in less than 60 seconds.

Each time, we've treated with about a cupful per month of "econo" brand CuSO4.5H2O crystals, down the commode and flush just before bed, so it has a chance to mix and distribute as slowly as possible. Things stay running clear as long as I remember to get it and use it. Then I get lax, and 6 months later - well, you-know-what happens.

I always wondered why the root-killer directions said to pour the whole 2 lb canister down the cleanout, just so I could watch my $12-$15 swoosh down underneath the roots, out the sanitary system (city dwellers) and into Lake Michigan. That's why I decided to add a little at a time.

My apologies for length, but here's some facts I found today:

Copper(II) Sulfate Pentahydrate only dissolves at 30 grams/100ml (@40 °F) of water, so the US average flush of 1.6 (ULF) to 3.6 gals (6 to 13.6 L) could dissolve approx 1 to 2.4 lbs (480 to 1080 grams) of crystals, then out to the environment.

Online sources absolutely recommend a foaming treatment or a foaming-additive and the plumber distinctly specified adding it to the commode before bed, so the foam would have ample time to activate, expand, and cover the pipe's entire inner circumference. Any wash-out occurs underneath the roots, and foam still clings to the roots.

More importantly, there's Diquat Dibromide, Metam Sodium (both no longer recommended) and Dichlobenil foaming chemical alternatives, but disallowed in some states and municipalities, and microbial/enzyme choices.

As for drilling 4 to 6 ft deep 1.5 to 2 inch dia holes around the lateral, (IMHO) good luck with that. I've used a 60 inch x 3/4" dia. electrician's bit to start steel posts, but I give the guy who fabricated his own hole-digger a lot of credit.

Here's some links for those interested:

William Gronitz
- Milwaukee, Wisconsin, USA

February 28, 2018

Q. Need help.

I have 2 septic tanks, the one connect to the drain field is filled with roots inside the tank!

Can I pour copper sulfate directly into the tank by opening up the tank concrete cover, will this help to kill the roots and also stop more roots coming into this tank!

Bob Warren
- Gloucester,Virginia

March 3, 2018

A. A septic tank is a small scale sewage plant and depends on the action of anaerobic bacteria. Copper has strong anti-bacterial properties. I would think very carefully before adding copper sulphate to a septic tank. Your nose will soon tell you if the bacteria are dead.

geoff smith
Geoff Smith
Hampshire, England

March 8, 2018

A. Bob,
A quick google search on the matter reveals there are specialty products for killing roots in septic tanks. Also, whoever does your routine septic tank cleaning could probably advise you on the best course of action.

ray kremer
Ray Kremer
Stellar Solutions, Inc.
supporting advertiser
McHenry, Illinois
stellar solutions banner

Will Copper Sulfate Damage Clay Drain Pipe?

December 20, 2018

Q. I just had my clay pipe drain line mechanically cleaned. I have flushed copper sulphate crystals down the toilet for 16 years which kept the line open until now.

Besides going through a notable root +/- 70 feet out, the technician who cleaned the line said that copper sulphate crystals will progressively damage the integrity of the clay pipe with use. Is this true? Specifically how will it damage clay pipe?

I searched but couldn't find much information on the web about this (arousing my suspicion), but still would like some unbiased information based on expert experience.

Rex Stambaugh
Home Owner - Denver, Colorado

January 10, 2019

Q. I found this question and I hope it's ok if I jump in & ask for help.
I'm wondering if I can get some help on using copper sulfate to kill roots in clay home drain piping.
A well-known plumbing company just got my clogged drains flowing but their video shows that roots are still growing in a few places where the pipe sections meet.
All 40 ft of PVC before the clay pipe is intact.
Their tool only bored a 2-1/2" hole thru some roots in the 4" clay pipe due to my 2-story slab foundation house only having a 2-1/2" clean-out in the garage that a tool could fit in. The video showed water flowing under the camera that was only about 1/2" deep.
They wanted to do an expensive Hydro-jet to clean out all of the roots.
Will copper sulfate soak up into roots to kill them if it is just occasionally flowing past the roots that are laying down in that 1/2" of waste water or does the pipe need to be partially plugged so that the copper sulfate touches all of the roots for a while?
Here's a PrintScreen from the video. Can somebody can help me learn what I should do with copper sulfate, which is legal to use where I live.


The drain pipe runs about straight out from where the clean-out is. The guy seems to have zeroed his camera when it went from the PVC into the clay as the DVD suddenly goes from 39' out back to 0'.

Jeff Davis
retired & on disability - Orange, California, USA

January 11, 2019

A. High pressure water through a ridged pipe makes a good cutting head for drilling in dirt, sand, but not very rocky soil. It also won't cut through your sewer line.

I found a 50 lb bag on Amazon for $104.00. They took off $60 for letting them issue their c card which I never intend to use. So I got 50 lbs for $44.

John Lyons
- Palisade Colorado USA

January 15, 2019

High pressure water through a ridged pipe makes a good cutting head for drilling in dirt, sand, but not very rocky soil. It also won't cut through your sewer line.

I found a 50 lb bag on Amazon for $104.00. They took off $60 for letting them issue their c card which I never intend to use. So I got 50 lbs for $44.

Q. Thanks John Lyons. They aren't planning on using it their Hydro-jet to cut thru anything outside of the sewer line but just the roots that have found their way into to splits between sections of the clay pipe.
So, I'm sure their Hydro-jet would clear the entire inside of the pipe of roots perfectly. My only real question is: how much copper sulfate should I use the first time and then how much/how often after that to keep new roots from growing or actually, I'd really prefer to skip their expensive $600 Hydro-jet and just kill what's left of the roots in their now.
From what you know, do you think dropping about 2, 4 or 6 lbs of copper sulfate crystals into the cleanout in the garage one night before bedtime and then flushing the toilet once would let some copper sulfate kill what you see in my photos and it those would just break off and go down into the sewer and then I could add a little maybe monthly at bedtime and let it seep in between the clay pipe's section divisions to kill any new growth it found?

Jeff Davis [returning]
retired - Orange, California, USA

simultaneous January 19, 2019

I'm still hoping for help on my simple questions that are in my last reply. Can somebody give me some very basic help on getting started using copper sulfate to kill the rest of the roots in my sewer lines and then to set up a preventative maintenance schedule?

Jeff Davis [returning]
retired - Orange, California, USA

January 18, 2019

Jeff Davis

My home made water jet was actually in response to some questions about drilling from the surface into the trench that the sewer line was passed in originally. I would really hate for someone to drill into their piping while attempting this with an auger.

My treatment plan is to flush 1/4 - 1/8 lb weekly/monthly when the house will be empty for several hours.

John Lyons
Homeowner - Palisade Colorado USA

January 22, 2019

Q. Thanks. That's similar to what I've read elsewhere. But most of them seem to say to use more the first time. One said to dump 2, 4 or 6 lbs in that first time just before bed & just flush the toilet once. I think I could do that pretty easily and if it was that much, I'd think dumping it into the clean-out in the garage would be the easiest way.
I'd like your opinion.
What's been also bothering me is, if the drain line isn't plugged, won't the water and copper sulfate just flow down in the lower 1/3 or 1/4 of that pipe out to the street, so will that even make contact with enough of the roots that I see in that picture I posted are growing in from different angles and not from all at the bottom of the pipe where the water usually flows?
Or do those roots have many little antennas so the ones that look like they're coming down from above are also connected pretty closely to others that are entering down in the sewage and will soak up copper sulfate and be shortened by killing them back a few feet each time I add some?

Jeff Davis
retired - Orange, California, USA

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