Downspout Strainers Catch What the Gutter Guard Misses

A gutter guard does its job in the trough. It keeps leaves, seed heads and shingle grit from settling in the channel, and it lets rain pass through to the outlet. The water then has to leave the gutter through a downspout opening at the low end of the run. That opening is often where the debris goes next, and a guard on the trough does nothing to stop it. If you are deciding whether to add guards to your St. Louis gutters, this is the part of the system that the guard leaves alone.

Where the debris goes after the guard

Water carries whatever gets past the guard into the downspout outlet. Maple seeds, small twigs and wet grit can collect in the opening, especially where the gutter has a slight low spot near the outlet. Once that happens, the water backs up in the trough and runs over the front edge, which is the opposite of what the guard was supposed to prevent. On a long run, one blocked outlet can send a steady stream of water down the fascia or onto the wall below.

Downspout outlets fail in a few predictable ways. The most common is a plug of wet leaf material packed into the opening. The second is a crimped or kinked elbow lower in the downspout, which holds back debris that never reached the outlet. The third is a downspout that is simply too small for the roof area it drains, so it fills during a heavy storm even when it is clean. A strainer addresses the first problem, and a correct downspout size addresses the third. The second needs someone to look at the elbow.

The types of downspout strainers

Most strainers fall into three groups. Each one fits a different opening, and each one has its own cleaning routine.

• Wire baskets sit inside the outlet and catch larger debris while letting water through the openings. They are inexpensive and easy to see, but fine grit can pass through them and collect lower in the downspout.
• Mesh cups or domes fit over or into the outlet and use a finer screen. They keep out more of the seed and grit, but a fine screen can also clog faster after a wet week, so it needs checking more often.
• Flip-up or hinged strainers open so you can clear the opening by hand without pulling the whole unit. They take more effort to install correctly, and they should be checked to make sure the hinge does not stick in cold weather.

None of these is a permanent answer on its own. A strainer is a filter, and filters need a service interval. On a yard with heavy maple or oak cover, the outlet may need a look at least once in the fall and again after spring seed drop. On a yard with few trees, a once-a-year check may be enough.

How the strainer should attach

A downspout strainer should stay in place through a freeze and a windy storm. If it rattles loose, it can drop into the downspout and create the blockage it was meant to prevent. Ask how the unit is held. Some sit in the outlet on a friction fit. Others are screwed or riveted to the gutter bottom or to the downspout collar. A friction fit is quick to install but can work loose as the aluminum expands and contracts through the year. A fastened unit holds better but leaves a small hole that needs sealing.

Check the fit at the outlet itself. The strainer should cover the full opening without pushing debris past the edge. If there is a gap along one side, leaves will find it. A strainer that is slightly undersized is worse than none, because it gives you a false sense that the outlet is protected.

Strainers and St. Louis freezes

Our winters swing through the freeze and thaw cycle several times in a season. Wet leaves that sit in an outlet can freeze into a solid plug, and a strainer does not prevent that. What it does is keep the bulk of the debris out of the opening, so there is less material to freeze in the first place. The ice still forms, but the outlet has a better chance of clearing when the next thaw arrives.

If you have had ice damming at the eave, check the outlet before anything else. An iced outlet can back water up into the trough, and the trough can then push water under the shingle edge. A strainer will not fix an ice dam, but a clear outlet keeps the gutter from adding water to the problem.

What to ask before you buy

Whoever quotes your gutter guards should answer these questions in writing. A quote that says "guards included" without naming the outlet treatment is leaving the most important detail out.

1. Which downspout outlets on my house get a strainer, and does the quote say so by location?
2. What type of strainer is it, and is it a friction fit or fastened?
3. How is the strainer sealed or secured at the gutter bottom?
4. Is the downspout elbow checked for crimps or kinks, and is that line in the scope?
5. How do I clear the outlet myself, and what tool does it take?
6. Does the downspout size match the roof area it drains, or was that not looked at?

The last question matters on larger houses. A single two-by-three downspout can be adequate for one run and badly undersized for another, and a strainer does not change the flow capacity. If your home has a long roof slope draining to one outlet, the strainer and the downspout size should be discussed together.

Cleaning the outlet without climbing the whole run

Most homeowners can clear a downspout outlet from the ground once the strainer is in place. Use a gloved hand or a plastic trowel to remove the packed material from the top of the strainer. Do not push a rigid rod down the downspout, because that can dent the seam or pull a fastener loose. Run water from a hose into the gutter after clearing to confirm the outlet is flowing. If water still pools in the trough, the problem is further up, often at the trough itself or at an elbow.

Ladder work is still the part that carries risk. If the outlet is high on a two-story wall, or if the gutter is wet and the ground is soft, call for help rather than leaning a ladder against the fascia. A strainer that is easy to reach from the ground is worth more than one that needs a climb every time it clogs.

If you are calling about gutters now

Keys Roofing can be reached at (314) 220-2333. When you call, ask about the outlet treatment before you ask about the guard brand, because the outlet decides how often the system needs attention. Describe the number of downspouts, the tree cover, and any spot where water has come over the front of the gutter. Those details will tell the person quoting the job whether a strainer alone is enough or whether the downspout sizing and elbows need a look first.