What is a downspout?

Downspouts run down the outside corners of the house, joined to the gutter by an elbow at the top and turned outward by another at the bottom. Follow yours to the ground and see what happens there. Three endings are common: a splash block, a hinged or roll-out extension, or a buried pipe carrying water off to a pop-up emitter or the curb. A buried line often shows itself as a short stub at the base of the elbow with no visible outlet. Note where each one lands, and whether it lands uphill of anything, because a downspout emptying onto a lawn that slopes back toward the house has accomplished nothing.

The volume explains the urgency. An inch of rain drops about 600 gallons on every 1,000 square feet of roof, so a modest 1,500 square foot roof in a 1-inch storm pushes roughly 900 gallons through its downspouts. Dumping that against the wall saturates the soil, drives hydrostatic pressure at the foundation, and finds the cold joint, the window well, or the hairline crack that lets it into a basement or a crawl space. The failures themselves are dull: a clog at the top elbow where gutter debris jams, a bottom elbow crushed by a lawnmower, an extension nobody put back, or an underground line silted shut. All four deliver the same water to the same wrong place.

Flush the downspouts twice a year, right after cleaning the gutters, by running a hose in the top and watching the bottom. Full flow means clear. A trickle means a clog: knock along the pipe with your knuckles, listen for the dull spot, then work it loose from below with a plumber's snake or a hose nozzle pushed up the outlet. Reattach extensions every time you mow. In freezing climates, pull roll-out extensions before the first hard freeze so an ice plug does not back water up into the gutter. Twenty minutes twice a year is what separates this from a wet basement.