Photograph of ammonia NOT being poured into a toilet Using Root Killers or Chemicals Over Septic System Components

  • USING ROOT KILLERS in SEPTIC FIELDS - CONTENTS: Advice on the use of root killers or roto-rooters for septic systems. How should I get rid of roots invading my sewer piping or septic system piping and drainfield?
  • POST a QUESTION or READ FAQs about the use of root killer treatments to control trees, shrubs, or other plants whose roots invade the septic system piping or leachfield (soakaway bed)

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Root killers for septic tanks, piping, drainfields? Advice on dealing with root invasion of sewer piping, drain piping, septic tanks, and septic drainfields.

This is part of our guide for homeowners who are planting trees, shrubs, gardens, ground cover, or other plants near a septic system and who need to know that can be planted near or over septic system components like the septic tank, distribution box, and drain field or soil absorption system.

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Using Root Killers or Chemicals In Septic Drainfields, Mounds, Raised Beds, Septic Tanks and other Septic Components

Planting the wrong things or in the wrong places can lead to the need for expensive septic system repairs. Planting trees, shrubs, and even some ground covers over septic system components are causes of septic system failure in the drain field, leach field, seepage bed, or similar components.

Planting fruit trees, or vegetables (or anything else edible) over the septic drainfield might produce food that is unsafe to eat: see SEWAGE CONTAMINANTS in FRUIT / VEGETABLES for details.

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Using Root Killers to "Un-Clog" Septic Pipes or to "Prevent Septic System Clogging"

We advise against using chemicals or caustics to "kill" tree or other plant roots which may be present in or near septic system components. People fearing that roots will clog or have already clogged their septic system piping, particularly drainfield piping, are tempted to buy these products. This is another example of a "magic bullet" that does not work, is dangerous, contaminates the environment, and is illegal in some jurisdictions.

Root killers as environmental pollutants: First, using a chemical to kill or to "prevent" invasion of roots in septic piping means you are pouring toxic chemicals and contaminants into the ground water - into the environment, and possibly right into your own or someone else's well and drinking water. This is a bad idea and is prohibited in many communities.

Root killers as a magic bullet to repair a septic system: Second, if septic drainfield or other pipes are already clogged or partly clogged with tree or other plant roots, even if you killed the roots in the pipe you're leaving the clogging material.

If piping in a septic system has become root-clogged, it is often the case that not only are the pipes clogged, they may be dislocated or even broken by the growing tree roots. You may find you've contaminated the environment, left the clog in place, and wasted your money since you'll still end up digging up the clogged line to replace it. [The photograph above is a simulation of pouring a chemical into the septic system through a toilet. Don't do this.]

Planting trees, shrubs, and even some ground covers over septic system components are causes of septic system failure in the drain field, leach field, seepage bed, or similar components. Planting fruit trees, or vegetables (or anything else edible) over the septic drainfield might produce food that is unsafe to eat:


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Frequently Asked Questions (FAQs) about septic system and drain piping root killers and invasion or blockage by tree, shrub, or other plant roots

Question: What liquid root killer can I use to kill the brush over my septic drainfield?

I have two septic tanks, the first seperates solids from liquid then sends the liquid to the second tank which has a septic pump that pumps the liquid UP to a drain field.

I want to kill brush over the drain field . The drain field is 1100 ft ABOVE my well . Is there a LIQUID root killer that I can use in this septic system as the copper pellets will never get up to the drain field and will sit in my seperator tank .

Can the copper pellets be ground into a powder - the powder mixed into a slurry that will be pumped to my drain field ? -

Reply: we do not recommend brush or root killers over the drainfield - remove the plants instead


We don't recommend chemicals and treatments in septic systems - search InspectAPedia for
"Septic System Additives & Treatments" for details.

Basically most such treatments are limited in effectiveness, risk damaging the environment, and are illegal in many areas.

If your drainfield piping is being invaded by roots we have found that even if you temporarily kill off roots in the piping they return in a year or two and repeat a costly clog. The solution is to either remove plants or excavate and install root passage barriers around the drainfield.

Take a look at PLANTS & TREES OVER SEPTIC SYSTEMS for details about planting over or near septic system components, and see USING ROOT KILLERS in SEPTIC FIELDS for our advice on the use of root killers in septic system tanks and drainfields.

Also see SEPTIC TREATMENTS & CHEMICALS for our explanation of the risks of using chemicals and other treatments in septic systems.

Question: Septic or sewer line treatment for redwood tree roots

What safe treatment is there for redwood tree roots...can I treat the end of root(s) I've exposed with something safe for aerobic bacteria in leach field? Can I 'paint' the end of the large root with something effective to kill only that root? Thanks. - Nanette


Nanette, my OPINION is that if you have large trees close to a septic drainfield their roots will continue to invade the field. If you kill off an individual tree root by cutting it back, the tree will send out new roots in its place. If you kill off enough roots to keep the tree out of the drainfield you'll likely kill the whole tree - a hazard of a different sort.

Those tree roots are pretty smart - good at seeking out water and the nutrients in septic effluent.

Reader follow-up:

Thanks for your opinion. My redwood trees are 50 ft. away, but one of those roots has somehow navigated upward, I have it 'confined' in a 3" abs pipe, so I could 'treat it individually, if I knew what to do/what product to buy. The leach field is protected both upward and downward by cement-block retaining walls. It has lasted for 30 yr. until this year's 'root clog'. I have dug up the leach field, cleaned the rocks, replaced the drain pipe system which is a gravity system, but now with 'vertical inspection ports', as well as a 'cleanout'/drop for root treatment separate from cement septic tank. I just need to know how to treat this one invasive root. SIGH. What can I pour into the pipe containing the root to kill just this one invasive root, safe for the San Lorenzo River 60 ft. away?


Nanette: impressive that those trees sent out a 50 foot root. Look there are "root killer" products sold to dump into septic systems to try to kill off tree roots. They have the down side of leaving dead roots in the system, no permanent solution to the problem, and in at least some cases, contaminating the environment. With the river less than 100 feet from your septic system I'd prefer not to use chemicals.

If you've got just one bad boy tree root that wandered 50 feet from the tree and into your septic, I'd try to follow the root back 20 feet or more from the septic system and cut it off there.

Reader follow-up:

I agree that I don't want to use chemicals, either, i.e., copper sulfate, etc.

However, trying to 'follow that redwood root back' is not trivial in my situation, as the root has grown 'upward' about 8-10 ft. above the ground level of the tree, and removing that depth of material is not as, ha,ha, as smart as the tree is.

I was hoping for something like say, rock salt solution, confined to that there no 'solution-solution', forgive me, for both the tree health (one root will not kill a redwood tree (coppice category), I am pretty sure it is not the 'tap root') and life-cycle leach field maintenance cost?

Thanks for your time in this discussion. Surely their is an environmentally harmonious way to solve this.

I am currently looking for information on 'root deterrents', which seem to be a better avenue of research than 'root killers.' So far, it seems that salt may be the 'solution'. Let me know if you have any further suggestions re environmentally conscious root deterrents than only the 'physical digging down 10 ft.' unusable suggestion in my case.


In short, dumping salt or chemicals into the soil is not a recommended practice, and as I warned earlier, it's illegal in some jurisdictions. The risk is that you contaminate a well, groundwater, or other surface and subsurface waters, not to mention that root killers and root deterrent chemicals are a short-lived band-aid for a problem of roots invading septic systems.

The solutions that work are to clear out pipes, cut back roots, or where practical, remove trees or plants that are invading septics - not so practical in your case where you have large distant trees.

Even more costly are "solutions" that move the septic fields or attempt to insert buried barriers.

Last, research by septic experts such as Minnis and Gayman confirm that putting any significant levels extra salt directly into the drainfield or sending it there via a septic tank or building piping is a quick way to destroy the drainfield. I'd be concerned about putting enough salt in or around a drainfield to kill or retard root growth since it is risking if not plain asking for very expensive drainfield damage as well.

Reader follow-up:

I do not disagree nor not care for the advice given, but am looking for a long-term solution to my problem.

As my drainfield lasted 30 yr., instead of the usual 10 yr, until 'large root impacted', and, as I have cut that root back 7 ft. and 'confined it' in a 3" diameter abs pipe, one cannot say that I have solved the problem by ignoring your advice....I AM sensitive to my forest and my river, which is how we got involved in our discussion in the first place.

What we seem to agree on is that only physical 'confinement'/'redirection' of the root is the best ecological solution. Hmmm...

what I HAVE done, is improve my leach field by removing/cleaning the rocks, replacing the leach line pipe including new 'vertical inspection ports', and cleanout, such that, perhaps, 'mechanical' removal of any invasive roots can be handled by annual inspection and 'mechanical removal'by 'snake' cutting before impaction.

I appreciate the input from you that mechanical options are preferred to chemical options.


Some mechanical approaches to avoiding use of chemicals to attack invading tree roots are in the next Q&A.

Question: tree roots are invading our septic tank; we cut down the tree but roots continue to be a problem

I had an elm tree near the tank and when the tank was pumped we saw the roots had penetrated the tank. We cut down the tree but it keeps coming back, which I assume means the roots are still alive and may continue to grow into the tank. Any suggestions on keeping the roots from finishing off the tank? I didn't plant the tree; it was there when I bought the place. Thanks, Cole

Reply: some mechanical approaches to keeping problem tree roots out of drain pipes & septic systems

Cole, persistent tree roots around septic components are indeed an annoying problem. Quite a few readers ask about using root killers. Our OPINION is that there is a risk of contaminating the environiment, such products (and all septic treatments) are actually illegal in many jurisdictions, and worse, years ago when we tried the most popular products we found that the root killer was not a long lasting repair - two years after de-clogging by removing roots from an invaded pipe and using root killer we had to clear the pipe again.

Other than manually digging out all of the invading root systems (and the stump) near your septic tank, you can reduce root invasion by making the septic system less attractive to and harder to invade by tree and other plant roots:

  • be sure that there are no groundwater leaks into the septic tank
  • be sure that there are no effluent leaks out of the septic tank (caused by a system that is backing up, failing, or damaged tank, piping, or D box).
  • replace problem piping that has been root-invaded using new PVC pipes with glued or gasketed watertight joints. A sewer or septic line that leaks effluent into the surrounding soils both attracts roots from nearby plants and it offers an opening through which roots enter the piping system.

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