A trough that looks clean can still be hiding a blocked pipe. This step-by-step flush proves that water runs from roof edge to discharge point, shows you how to read the result and covers the winter and buried-drain cautions.
In This Article
Why the flush is the real test
Scooping removes what you can see. The flush shows what you cannot: a low spot that holds water, a joint that leaks under load, an outlet half-blocked by a leaf, a downspout crushed since last year. Rain will run this test for you eventually, so it is better to run it yourself on a dry day.
Do it every time you clean, even when the troughs looked easy. It adds about ten minutes and turns a job you hope worked into one you know worked. It also gives you a baseline: note roughly how long each downspout takes to show a full stream, and next year a slower one stands out at once.
Before you turn on the hose
- Finish scooping first. Flushing a trough that is still full of muck just pushes it into the downspout.
- Lift out any outlet strainer or basket, and clear the leaves around the base.
- Check the discharge point. The extension should be attached, sloping away and free of leaves, with nothing stored in its path.
- Divert a rain barrel, if you have one, so it does not overfill.
- Set the hose to a steady, moderate flow. Save the nozzle blast for stubborn spots. Do not use a pressure washer, since it can split seams and throw debris at the wall.
- Look at the weather. Do not flush if freezing is due within hours (see the winter notes below).
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The flush, in order
- Start at the end of the run farthest from the downspout. Water should travel with the slope toward the outlet.
- Wet the trough first, then increase the flow, so loosened grit and fine debris travel along with the water.
- Watch the bottom of the run. Anywhere the water slows, pools or backs up is a low spot or a blockage.
- Move to the downspout. Point the hose into the outlet and watch the discharge at ground level.
- Run a full-flow test for a minute or two, to imitate a hard rain. Look for drips at seams, end caps and elbows.
- Check where the water lands. It should leave the extension and move away from the house, without pooling by the wall.
- Repeat on every run and every downspout, then turn off the water and look for puddles in the trough. None should remain.
Reading the result
| What you see | What it means | What to do |
|---|---|---|
| A strong, steady stream at the bottom, close to the hose flow | The pipe is clear | Nothing. Move on to the next run |
| A weak stream or gurgling | A partial blockage in the pipe | Flush again from the bottom, or use a plumber's snake at the elbow |
| Water backs up into the trough | A full blockage | Clear the outlet and the elbow, then repeat the test |
| Drips at a seam or end cap | Failed sealant | Note the spot and reseal on a dry day |
| Water lingers in one part of the trough | A sag or low spot | Mark it. It needs re-hanging, not more flushing |
| Water pools at the wall | The discharge is too close or slopes the wrong way | Lengthen or redirect it |
The downspout extensions guide covers how far to carry the water and what to attach.
Winter and buried-pipe cautions
Freeze-thaw cycles are common from November to April, so timing matters late in the season. If water is still standing in a pipe after you flush, the pipe is blocked, and that water can freeze and split the seam. Flush in the middle of a mild day, and leave it for a thaw if a hard freeze follows. Never chip ice out of a pipe.
If your downspouts drop into a buried pipe, flush at a moderate flow and confirm that water actually leaves the system. Check your municipality's current rules before you change or disconnect a buried connection. Underground downspout drainage explains how these lines work and why they freeze.
If you would rather hire it out
Ask any crew whether downspouts are flushed and how they prove the water runs, and get the answer in writing. D&D Home Services offers gutter cleaning from $125 for a typical Kitchener-Waterloo home, with free quotes confirmed in writing before work begins. A written scope that names the downspouts is the easiest way to compare quotes.
Key Takeaways
- A flush proves the water runs from the trough to the discharge point, which a visual check cannot do.
- Finish scooping first, use a moderate hose flow, and work from the end of the run farthest from the downspout.
- A strong stream means the pipe is clear. Weak flow, backing up, drips, lingering water or pooling at the wall each point to a separate fix.
- Do not flush when a hard freeze is due, and take care with buried connections.
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