How to Check for a Blocked Downspout Safely

A downspout that stops running while the channel above it is full has something inside it, and most of what you can do about that is done standing on the ground. Watch the outlet through one rain, look over the bottom of the pipe and its extension, clear what your hand can reach, and flush the run from the discharge end. Two checks sit outside that work. The outlet and the strainer at the top of the run are at the roof edge, and anything below the discharge point is a drain rather than a downspout. Water over the front edge of the gutter generally, and whether the cause is a blockage, a lost fall or a run too small for the roof, is sorted on its own page. The system as a whole, and the choice between cleaning and repair, is set out in the gutter maintenance guide.

Do nothing until you have watched it rain

The one observation that settles whether a downspout is blocked costs nothing and needs no tool. During a real rain, stand inside the property line and note two things at each run: whether water is leaving the bottom of the downspout, and whether the channel above the outlet is full at the same time.

A run that is full above while its downspout delivers nothing, or delivers only a trickle, is not passing water. Three further conditions belong to the same check, and each one appears in the maintenance lists read for this page: spillover near a foundation, a joint or fitting that is leaking, and eroded soil below a discharge point. That is the whole of the check, and it needs nothing but the rain.

Where a downspout collects material

A downspout is a mostly straight pipe with bends at each end, and the material inside it comes from one place. Snohomish County’s surface water programme makes the point directly: the outlet is where the strainer sits, collecting exactly the material the gutter delivers to it.

The sources that write this work down name four collection points:

• The outlet at the top, where the gutter discharges into the pipe, and the strainer inside it.
• The bend just below the outlet. The manufacturer’s sizing appendix used for gutter capacity notes that “a sharp bend at the inlet may clog.”
• The bottom elbow and whatever is attached to it — the extension, the connector, the splash block.
• The buried drain below the discharge point, which is a separate system with its own symptoms.

Only the first of those sits at the roof edge, and only the last is below ground. Everything between them can be reached, checked and often cleared from a standing position.

The ground-level checks

1. Say which runs are failing. Take the note from the rain observation, so you know which pipe to work on.
2. Put on gloves and eye protection. Clark County’s downspout guidance opens its work steps with heavy duty work gloves and eye protection, and what a blocked pipe releases is the reason.
3. Look over the bottom of the run. The extension, the connector and the splash block are the parts you can see and handle without a ladder. Check that the pieces are joined and in good repair, because the county maintenance standards list cracked, collapsed, broken and misaligned pipe among the defects to correct, and that the mouth is clear.
4. Clear what your hand can reach. Loose material at the discharge point comes out by hand far more often than it needs a tool.
5. Flush the run from the discharge end. Clark County’s maintenance manual states that “the most common tool for cleaning these systems is a hose to flush downspouts,” and the state’s low-impact-development guidance gives the same instruction for a plugged pipe: clear the screen and the pipe. A high-pressure nozzle on a hose, worked in where the downspout meets the ground, will loosen what the hand could not reach.
6. Check the joints while you are there. Clark County’s flier closes with the maintenance rule that connections must be secure and not leaking, because a joint that has opened moves water onto the wall instead of into the drain.

The outlet and the strainer, and where the safe work ends

Snohomish County describes the part that causes much of this trouble. A wire mesh or plastic strainer sits inside the downspout inlet, the county states, and fills with debris; a strainer cup can be retrofitted so that it pulls out for cleaning and inspection. The same maintenance list adds the outlets that are easy to forget — the ones under decks and staircases. Clark County’s manual adds the design point beside it: keep the gutter free of debris and sediment, or fit a downspout insert that keeps material out of the pipe while still letting water pass through.

The inlet itself is at the gutter, and the gutter is at the roof edge. This publication’s position, stated in its gutter guidance, is that the roof edge is where household work stops. When the only check left is the outlet at the top of the run, that is the stopping point.

Where a check does mean a ladder, the federal guidance exists because the hazard is real, and its limits are the reason to stop rather than a method to copy: keep ladders and tools at least 10 feet from any power line, and keep three points of contact rather than carrying anything while climbing. The manufacturer’s own ladder instructions govern the ladder. This page sets out no ladder work.

Freezing changes the answer

A pipe that will not drain holds water, and in freezing conditions that water becomes ice. Ice is not a blockage you clear. The manufacturer’s sizing appendix gives its advice for areas subject to icing in design terms: open, partially open or corrugated downspout styles are suggested there, and a downspout on the north face of a building is not recommended. The publication’s own reading of the advice is the practical consequence — a run that froze held water before the freeze — so the way to leave nothing in the pipe is to clear it while it can still drain. Clearing a run often enough that it does not carry standing water into winter is the frequency question, and it has its own guide.

When the trouble is under the ground

Take the extension or the bottom elbow off, then flush the open end. If the downspout runs freely and the water still backs up, the blockage is not in the downspout at all.

Portland’s stormwater guidance names what to inspect at that stage: the standpipe for clogs, and for looseness or cracks below the surface. A buried drain, its route and its repair are a different subject from the pipe on the wall, and the checks for one belong with drainage rather than with gutters. The useful observation a reader can still make safely is where the water surfaces during rain, because a buried inlet that has been lost under soil and planting can show itself by where the water seeps out.

What comes out, and where it goes

Whatever the run releases — leaves, needles, roof grit, the packed material in the bend — is yard waste with a destination. The Department of Ecology states that dumping yard waste into state waters or storm drains is illegal, and that it can bring fines from the state or from the local jurisdiction. Its own alternatives are a compost bin, the curbside yard waste container from your hauler, and a yard debris drop-off site. Curbside service varies by hauler and by jurisdiction.

Next step

Watch the next rain inside the property line and write down which runs fail. Then work from the bottom upward: check the parts you can reach, clear them by hand, flush the run from the discharge end, and look for a joint that has opened while you are there. If the pipe runs clear and the trouble remains, you have a drainage question and not a downspout one. If the only check left is the outlet at the roof edge, that is the point to hand it to someone who works there. Whether a cleaning is a household job or a professional one at all is decided by access, not willingness.