Direct answer: A buried downspout is usually crushed when water backs up at one downspout, the gutter above it overflows in rain, and probing or flushing stops hard at the same spot every time. Start by confirming it is a collapse and not just a clog at the outlet or elbow.
Most likely: The most common real-world cause is a shallow buried extension that got flattened by foot traffic, a vehicle tire, settling soil, or roots squeezing a weak section.
A crushed underground downspout line acts different than a simple clog. A clog often gives you some flow, then slows. A crushed section usually hits a firm dead stop in the same place and keeps backing water toward the house. Reality check: most of these failures are in the first several feet or at a driveway crossing, not somewhere mysterious in the middle of the yard. Common wrong move: blasting harder with a pressure nozzle can split a weak buried line and make the repair bigger.
Don’t start with: Do not start by buying random fittings or digging the whole yard open. First find whether the problem is at the outlet, near the house, or in one short buried section.
Water spills from the top elbow or connection near the foundation as soon as the gutter starts draining.
Start here: Check the above-grade elbow, the first buried connection, and the first few feet of pipe before chasing the far outlet.
The gutter and downspout are full, but little or no water reaches the discharge point.
Start here: Clear the outlet opening first, then test whether a hose or probe stops hard at one repeatable distance.
You see a dip, rut, or soggy strip where the buried extension runs.
Start here: Suspect a collapsed or split section in that area, especially if it crosses a walkway or driveway edge.
The problem started after a truck, mower, skid steer, or heavy foot traffic crossed the route.
Start here: Look for a shallow section that may have been flattened rather than clogged with leaves.
This is the most common cause when the line worked before and now stops solid at one spot, especially near a driveway edge, walkway, or low area.
Quick check: Run a drain probe or hose from the downspout side and note the exact distance where it stops hard. Compare that distance to the route on the ground.
A blocked discharge end can mimic a crushed line because water backs up fast, but the fix is much simpler.
Quick check: Find the outlet and clear grass, mulch, leaves, or a packed dirt lip. Then retest before digging.
The first elbow and adapter take a lot of abuse from ladders, weed trimmers, and settling soil, and they fail more often than the middle of the run.
Quick check: Remove the lower downspout connection if accessible and inspect the elbow and first buried fitting for deformation or separation.
If the line still takes some water and then slowly backs up, you may have a leaf-and-shingle clog instead of a true collapse.
Quick check: Flush with a garden hose at moderate flow. If water trickles through or the blockage shifts, think clog first, not crushed pipe.
A buried outlet blocked by grass, mulch, or a dirt berm is common and looks a lot like a crushed underground run.
Next move: If water now flows freely and the backup at the house stops, the line was not crushed. Keep the outlet clear and monitor it in the next rain. If the outlet stays dry or only burps a little water while the downspout backs up, keep going.
What to conclude: You have ruled out the simplest outlet blockage and can focus on the buried run or the connection near the house.
A lot of 'underground crush' calls turn out to be a smashed elbow, a slipped connector, or a failure in the first foot below grade.
Next move: If you find a crushed elbow or separated connector right there, repair that local section and retest before digging farther. If the opening looks sound but the probe stops farther out at a repeatable distance, move on to locating the damaged section.
What to conclude: This separates a near-house fitting failure from a buried line failure, which saves a lot of unnecessary digging.
You want one clear target before you dig. A crushed section gives a firm stop in the same place. A clog is usually softer, wetter, and less consistent.
Next move: If both direction checks point to one short area, you likely have a crushed section you can expose and replace locally. If the stop point changes, water slowly seeps through, or the whole run seems packed with debris, treat it as a clog problem first rather than a crush.
Most buried downspout crush failures are local. Replacing a short section is usually enough if the rest of the run is intact and sloped correctly.
Next move: If water moves freely and the repaired section stays round under light backfill, finish backfilling and restore the surface. If the line still backs up after the damaged section is replaced, there is likely another collapse, a downstream clog, or a bad slope farther along the run.
A buried line can have more than one problem. You want to prove the repair under real flow before you close the job.
A good result: If the line carries full flow without backing up, the repair is done.
If not: If water still ponds, backs up, or disappears into the soil, the problem is bigger than one crushed section.
What to conclude: Either the local repair solved it, or you now have enough evidence to justify a deeper clog or grading investigation instead of more guesswork.
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A crushed section usually gives a firm dead stop at the same distance every time you probe it, and the outlet often stays dry. A clog is more likely to feel soft or inconsistent and may still let some water trickle through.
Most failures show up near the house, at the first bend, at shallow sections, or where the line crosses a traffic path. Settling trenches and driveway edges are common trouble spots.
If you expose one clearly crushed area and the rest of the line is sound and flowing, a local section repair is usually enough. If the pipe is brittle, misshapen in several places, or still backs up after one repair, the run may need broader replacement.
Not if the pipe is actually flattened. A snake may stop at the collapse, and aggressive pressure can split weak pipe or blow apart joints. Use probing and moderate flushing to diagnose first.
That usually moves out of simple DIY territory. You may need specialized boring, saw cutting, or rerouting, and it is worth getting a drainage contractor involved before you start breaking hardscape.
Not by itself. Wet soil can also mean a split joint, a clogged outlet, or overflow from the top connection. It is a strong clue when it lines up with a repeatable hard stop during probing.