A clog you clear once is a nuisance. A clog that keeps coming back is a message. When the same drain backs up every few weeks no matter how many times you plunge it or pour something down it, the blockage you keep removing is a symptom, not the actual problem.
Here are the seven most common reasons drains clog repeatedly in Portland-area homes, and what it takes to fix each one for good.
1. Grease and fat buildup
This is the leading cause of kitchen drain clogs, and the trickiest because it is invisible. Cooking grease goes down the drain as a hot liquid, then cools and hardens onto the pipe walls a few feet down. Over months, the opening narrows like a clogged artery until water can barely pass. Pouring boiling water down only melts it temporarily. It re-solidifies further along the line.
2. Hair and soap scum
In bathroom sinks, tubs, and showers, hair binds with soap scum to form a dense, fibrous mat that catches everything else flowing past. It is the most common bathroom culprit by far. A simple mesh drain screen stops the vast majority of it before it ever enters the pipe.
3. Things that should never go down the drain
So-called “flushable” wipes are anything but. They do not break down the way toilet paper does and are a leading cause of serious clogs. The same goes for cotton swabs, dental floss, feminine products, and coffee grounds. If it isn’t water, waste, or toilet paper, it belongs in the trash.
If one fixture clogs repeatedly, the problem is usually local to that drain. If multiple fixtures back up at once, or you hear gurgling in one when you run another, the issue is deeper in the main line, and that is a different conversation entirely.
4. Tree roots in the sewer line
Here is where repeated clogs get serious. In older neighborhoods, tree roots invade sewer lines through tiny gaps at the pipe joints, then grow into a mesh that snags waste and triggers backups. You clear it, flow returns, and a few months later the roots have grown back. If your whole-house drainage slows on a recurring cycle, roots are a prime suspect. The only way to confirm it is to look: a video sewer inspection shows exactly what is happening underground.
5. A sagging pipe (a "belly")
Over time, ground settling can cause a section of pipe to sag, creating a low spot where water and waste collect instead of flowing through. Material accumulates in that dip and clogs form there again and again. No amount of plunging fixes a belly. It is a physical low point in the line that needs to be located and corrected.
6. An older pipe surface that grabs everything
Decades-old cast iron and clay pipes develop rough, corroded interior walls. That roughness catches debris that would slide right through smooth modern pipe. The clogs aren’t your fault. The pipe surface itself has become a snag point. For lines like these, hydro jetting scours the walls back to near-smooth, something a basic snake can’t do.
7. The clog was never fully cleared
A drain snake often punches a hole through a blockage rather than removing it. Water flows again, so the job seems done, but most of the obstruction is still clinging to the pipe walls, ready to rebuild within weeks. This is why a proper clearing matters more than a quick poke.
How to actually break the cycle
Repeated clogs almost always trace back to one of two things: a habit that keeps feeding the drain the wrong stuff, or a structural issue in the line itself. The fix depends on which:
- If it is habits: a grease can by the stove, mesh screens on every drain, and a "trash, not drain" rule for everything but water, waste, and toilet paper will eliminate most recurring clogs.
- If it is structural: you need to see inside the line to know what you are dealing with. A camera inspection finds roots, bellies, and corrosion; then the right clearing method, from a thorough drain cleaning to hydro jetting, resolves it properly.
The best decision comes from matching the system to your home’s actual hot-water demand, fuel type, and layout, not from a spec sheet. That is where an in-person assessment pays off.
Thinking about your options before your current unit gives out? Our team installs and services both system types every day. Learn more about our water heater services or give us a call. We will help you choose the right one the first time.
The Lovett Plumbing Team
Licensed Portland plumbers serving the metro since 1997. CCB #125507.
