My septic tank is filling up far too fast. I think the system is being compromised by roots. But could this be caused by something else?—Pete Clancy, via email
Well, you’re not wrong to blame roots. “Tree roots are one of the leading causes of issues with a septic system,” says Bill Goodale, a project manager with Tatham Engineering and a sewage system inspector for the Township of Tiny, Ont. Spoiler alert: if the tank and leaching bed are surrounded by trees, then, yes, the system could be compromised by roots. Stronger evidence would be “if you take off the septic tank lid and, on the outlet side, see roots coming into the tank,” says Goodale. They don’t have to belong to trees; lots of shrubs with deep roots can also monkey with a septic system.
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If roots are the problem, you’ve got to remove them. This’ll involve digging to expose the pipes—you can’t get roots out of the ground without knowing where they start and finish. First, check if you need a permit, says Goodale. (Also, PSA: if you’re in Ontario and digging anywhere, you’re really supposed to check in with Ontario One Call.)
But there are lots of other reasons that a tank could start to fill up too fast. For example, a crushed pipe leading to the drainfield, or a blockage somewhere. Maybe someone’s been flushing items that they aren’t supposed to.
Excess water getting into the tank—even from a single dripping tap—can also cause the tank to fill up rapidly. “A drip or a trickle in one fixture doesn’t seem like a lot, but twenty-four hours a day, seven days a week, it adds up,” says Goodale. “It’s surprising how much it adds up.”
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Have you started visiting the cottage more often, or hosting more guests? A big change—more people suddenly using the cottage more frequently—can be “a bit of a shock to the system,” says Goodale. There could have been small, underlying problems with the system for years, “but with minimal use, they didn’t really show up.”
Maybe you’ve ruled out all the obvious reasons for this septic issue. If that’s the case, the next time you call the sewage hauler, be there for the pump-out, says Goodale. “Ask the person what they think is going on. If the tank is filling up too fast, you need to get to the root of the problem,” he says. “Pun intended.”
Got a question for Cottage Q&A? Send it to answers@cottagelife.com.
This article was originally published in the June/July 2025 issue of Cottage Life.
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