When trees attack!

We typically think of trees as the ‘good guys’; they shade our homes and yards, they take up carbon dioxide and pollutants from the air, they give us oxygen.  What’s not to like?  Well, like a lot of good guys, trees can also have a dark side.  One of the more sinister habits some trees have is getting into sewer lines.  Some studies estimate that trees are responsible for up to half of sewer line repair costs.  The prospect of trees getting into residential sewer lines is troublesome, of course, because it’s an invisible problem; we usually don’t know there’s an issue until there’s an issue.  Once tree roots get into sewers, they are often expensive and messy to deal with.  And I don’t mean just messy in the sense of having to call in a backhoe to dig up your yard.  Deciding who is responsible for the cost of cleaning up after a tree figures out its hit the mother lode can be a mess as well.  What if your neighbor’s sycamore finds its way into your pipes?  Or what if the culprit is the silver maple that you didn’t want but the city planted in the tree lawn anyway?  In some cases there are city ordinances that cover these situations.  For example, some cities will cover damage from city-owned trees provided they determine the city-owned tree caused the damage and the damage wasn’t due to a pre-exiting problem with the pipes.  Therein lies the rub.  As long as sewer pipes are intact and functional, tree roots have a hard time penetrating.  The problems usually arise when pipes crack or joints fail.  Once roots find an opening, it’s Katie bar the door.  This is why tree-sewer problems are most common in older systems with clay or concrete pipes that can crack over time.  Of course, the type of tree and location play a role as well.  Other factors being equal, fast-growing bottomland species are the most frequent offenders.  Danish researchers found that willow, birch, and poplar trees were responsible the largest number of root intrusions into sewer lines.  In many parts of the US, sycamore, sweetgum, and tulip-poplar can be added to the list.

Tree roots and sewer lines: a bad combination
So what’s a homeowner to do to get some sleep and not worry about tree roots planning a silent assault on the drain-lines?  Keeping fast-growing trees away from lines is a start.  But tree roots can grow a long ways and are pretty relentless; if there is a crack or a weak spot in the pipes, they will find it.  Keeping the system maintained and preventing entry is the key.  If the system has cracks, “Root-stopper” or “root-killer” products are available.  These are copper-based materials similar to ‘spin-out’ used on tree containers to prevent circling roots.  These will kill feeder roots that have entered into pipes, but roots are persistent and they’ll be back.  Plumbers have special tools that they can snake through the system that can cut through roots and clear blocked lines – at least for awhile.  If you have old sewer lines and have fast-growing trees around, you may want to consider hiring a plumber do a video inspection of your lines periodically (think of it as a colonscopy for your house).  If there’s a problem the plumber will be able to pin-point where it’s at and (hopefully) fix it before it becomes a major expense.

14 thoughts on “When trees attack!”

  1. Bert (and/or other Garden Profs):

    Care to share your thoughts on why tree roots actually end up clogging sewers?

    Is it the nutrients, the moisture, or . . . . something else that drives them to thrive?

  2. Oh, but we make our living by replacing sewage disposal systems that trees have clogged beyond hope. It’s not uncommon for people to refuse to remove a maple that they have been told will destroy their expensive system a few years down the road. I guess the beauty of a tree beats the probability of expense down the road. People amaze me.

  3. What an appropriate post. My plumber has recommended that we remove a tree in our front yard because it was planted right on top of the sewer line. And said tree has already caused major damage to the sidewalk. Send a scope down the drain to see if there’s damage? I’m afraid to look!

  4. Are tree roots part of the problem with the gas line problems that seem to be showing up more often in the news?

  5. Some of these trees don’t just tear the pipes they tear up sidewalks, roads, and are so weak wooded they drop limbs on power lines and on cars and street sweepers knock off limbs. We have a small urban parkway and I had to go to Fire Marshall to get the Silver Maple that was on it removed. I replaced it with a smaller, much more manageable fruit tree. I think in urban areas a full size tree is not always the answer for the parkway; sometimes a decorative shrub or small understory tree is the way to go.

  6. Great post SJ. I think this is something cities need to think about. Sidewalks, utilities, sewers there are a lot of things that large trees can get into in city lots.
    Terry, I think it’s just a combination water and nutrients. Technically speaking roots don’t ‘seek out’ water and nutrients but they are very good a proliferating once they reach a place where the gettin’ is good.

  7. I recently hired a plumber to come into my home, because a water leak was causing damage in my basement ceiling. He said my freezer on the main floor was thawing and refreezing and causing the refrig drip pan to over flow. I got a new refrig. The water leak continued. It took a total of four plumbers before the cause was found to be tree roots in my ouside sewer line. My home insurance will not cover tree root damage and they will not accept that there may have been two sources of water damage: the refrig and the roots. Is is possible that the increased water pressure from the blocked sewer line could have caused my refrig to begin to thaw/refreeze. I have full coverage for damage due to refig malfunction and none for tree root damage. Needless to say, my home insurance company benefits if all the extensive damage is blamed on the roots. I have no idea what the truth is. Any input will be greatly appreciated. Thanks. Lynn

  8. I am currently having my drive dug up to replace the old lines with PVC due to roots “Wicking” the water out of line and depositing it 50 feet in my yard! Just amazing. Here is my questions – I also have 4 inch roots running in my crawl space floor. Should I chain-saw them or leave them there? They are under the foundation wall it appears.

  9. First of all Ron, we want pictures! This sounds like something that needs to be on the blog.

    I’m hesitant to offer advice sight unseen – especially when the structure of a home is involved. My best advice is to have a professional to look at the situation first-hand. My initial reaction is to get the roots out of there before they do any(more) damage but there may be unintended consequences that might become apparent during and on-site inspection.

  10. the company i work for offers epoxy sewer lining. if the existing pipe can be clean, a new pipe can be sleeved in with no connections for roots to get in through, and no digging required

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