Downspout blockage: repair options from rod to re-route
Clear a blocked downspout for $150 to $400, replace a crushed 12-foot run for $108 to $240, and clear a buried drain for $200 to $600. What each option fixes.
A blocked downspout is cleared by rodding and flushing at $150 to $400. A crushed section is replaced for $108 to $240 on a 12-foot run, and a buried drain is cleared or re-routed for $200 to $600. Most blockages are at the outlet.
- Rod and flush
- $150 - $400
- Replace 12 ft run
- $108 - $240
- Clear buried drain
- $200 - $600
- Outlet strainer
- $10 - $40
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A blocked downspout is cleared for $150 to $400 by rodding and flushing, and the blockage is almost always in one of three places: the outlet strainer, the bottom elbow, or a buried drain. Replacing a crushed 12-foot section costs $108 to $240, and clearing a silted buried line costs $200 to $600. Knowing which one you have decides whether the job is an hour or a day.
What a downspout blockage actually is
A downspout is a vertical pipe that carries roof water from the gutter to the ground. It is the narrowest part of the drainage system, so it is where debris collects: shingle grit, leaf fragments, nest material, and ice.
The pipe itself rarely fails. What fails is the flow path at one of three constrictions, and each has a different repair.
The four blockages and their repairs
| Blockage | How to tell | Repair | Cost |
|---|---|---|---|
| Outlet strainer packed | Water backs up at the gutter outlet | Clear the basket | $150 - $400 |
| Bottom elbow packed | Water exits the pipe at the joint | Remove elbow, rod, refit | $150 - $400 |
| Pipe crushed or split | Dented section, water on the wall | Replace the length | $108 - $240 |
| Buried drain silted | Pipe clear above, water pools at grade | Jet or re-route | $200 - $600 |
| Ice plug | Blocked only in freezing weather | Clear and improve fall | $150 - $400 |
The first two account for most calls. The third is visible from the ground as a dent or a separation at a joint. The fourth is the one that gets misdiagnosed, because the downspout looks clear and the water still does not leave.
Clearing from the ground
The safe method works from the bottom. Roof work on a wet day is the wrong place to solve a blockage, and a hose fed from the top often just compacts the debris further down.
- Remove the bottom elbow or the splash block so the pipe end is open.
- Feed a garden hose with a nozzle up the pipe, or a drain snake if the blockage is solid.
- Work the hose up in short pushes, letting water run back out between them.
- Flush until the water runs clear at the bottom and the gutter drains within a minute.
- Refit the elbow and check the joint for leaks.
- Fit a strainer at the gutter outlet so the next load of grit stops at the top.
Step six is the one that prevents a repeat. A downspout without a strainer is a grit trap with a fixed service interval.
Why the elbow blocks first
An elbow is the only place in the system where the flow changes direction, and a change of direction is where solids drop out of suspension. Grit and leaf fragments travel down the vertical pipe at speed, hit the bend, and settle in the pocket on the outside of the turn.
That pocket fills from the bottom up. The pipe stays partly open for months, so the first symptom is not a complete blockage but a slow drain, and a slow drain is what lets water stand in the gutter long enough to overflow at the outlet.
The fix is mechanical: remove the elbow, clear the pocket, and refit. The prevention is the strainer at the top, because grit that never enters the pipe cannot settle in the bend.
When the pipe has to be replaced
Aluminium downspout dents and splits at the elbows, and a split joint leaks down the wall rather than away from it. Replace the affected length rather than the whole set.
At $9 to $20 per linear foot installed, a 12-foot run is 12 × $9 = $108 at the low end and 12 × $20 = $240 at the high end. A full set of four runs on a two-storey house is $400 to $1,000. The arithmetic is in downspout installation cost.
Replacement is the right call when the pipe is crushed behind the siding, when the joint has pulled apart and cannot be re-seated, or when the metal has corroded through at the bottom where water sits.
Buried drains and the invisible blockage
A buried drain carries the downspout discharge away from the foundation to a pop-up emitter or a dry well. It silts up over years, and the symptom is water pooling at grade while the downspout above runs clear.
Clearing it needs a jetter, not a hose. Expect $200 to $600, and ask whether the contractor will camera the line. If the pipe has collapsed or the run is too flat to drain, re-routing to a surface discharge with an extension is often cheaper than repeated clearing.
What the blockage has already done
Water that cannot leave the downspout backs up into the gutter and overflows at the outlet end. That puts water behind the fascia and at the foundation, which is where the real cost appears.
Check the fascia at the outlet for staining and soft wood, and check the ground for erosion within 3 feet of the wall. If the wood is soft, fascia repair at $6 to $12 per linear foot is part of the job, and the downspout is the cheap line.
The short version
Clear the outlet and the elbow, replace a crushed length, and jet a buried drain. Budget $150 to $400 for the clearing and $108 to $240 for a replacement section, and fit a $10 to $40 strainer so the job does not repeat. The prices by scenario are in downspout blockage: what a fix costs, the warning signs are in downspout blockage: warning signs, and the overflow that follows is covered in water overflowing: repair options.
Frequently asked questions
How much does it cost to unblock a downspout?
Between $150 and $400 for a contractor to rod and flush it. If the pipe is crushed or the section has to come off, a 12-foot replacement at $9 to $20 per foot is $108 to $240 on top.
Can I clear a downspout myself?
Yes on a single storey. Remove the elbow at the bottom, feed a hose or a drain snake up from the ground, and flush until the water runs clear. Work from below, not from the roof.
Why does my downspout keep blocking?
Usually because the outlet has no strainer and the gutter above it collects shingle grit. The grit washes into the elbow, which is the narrowest point, and packs there. A $10 to $40 strainer solves most repeat cases.
How do I know if the blockage is underground?
If water backs up at the bottom of the downspout while the pipe above is clear, the buried drain is blocked. That is a different job, priced at $200 to $600 to jet or re-route.
Does a blocked downspout damage the gutter?
It causes the gutter to overflow, which puts water behind the fascia and at the foundation. The gutter itself is usually fine, but the fascia and the soil are not.
Should I replace the whole downspout or just the blocked section?
Replace the failed section. A crushed or split 12-foot length is $108 to $240; replacing the whole set of four runs is $400 to $1,000, which is only worth it if the pipe is at the end of its life.
Sources
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