Buried Downspout Extensions in Farmington Hills

A pop-up emitter is a cap at the end of the line, set flush with the lawn. When water fills the pipe, the lid lifts and the water spills out across the grass, and then it drops shut. It needs to sit lower than the downspout and on ground that keeps falling away from the house. Our view on emitters in a Michigan winter: the last few feet of pipe can hold water that freezes, and a frozen emitter backs water up to the downspout. A small gravel pocket under the emitter, or a weep hole at the low point, lets the line drain between storms. Keep the emitter out of the path of a walk or driveway apron, where its outflow can freeze into a sheet of ice.

Where there's no slope to daylight and no storm sewer to reach, a downspout line can end in a buried dry well. The size comes from the roof. One inch of rain on 1,000 square feet of roof is roughly 620 gallons, by USGS's figures, and the National Weather Service's 1991-2020 normals for the area come to about 34 inches of precipitation a year. A 250-gallon well under one downspout fills quickly in a summer storm if the clay around it drains slowly. Ask for a percolation test, and expect an overflow emitter above the well. HomeGuide suggests setting a dry well about 5 to 6 feet deep so it doesn't freeze, and cleaning it out once a year. Dry wells as a yard-wide fix are on the yard drainage page.

Running a downspout line to the street or a storm structure gets the water off the lot entirely. The city's storm-drain ordinance allows stormwater into the storm system, and its sewer ordinance makes it unlawful to send roof water into the sanitary sewer. What we haven't found is a city rule on cutting a line through the curb. Work inside a city road right-of-way needs a right-of-way permit from the DPS Engineering Division (248-871-2560; $75 for a residential permit), so call them before anyone saws the curb or taps a storm inlet. Don't borrow the city's sump rules for this either. The 4-foot and 20-foot distances in the sump discharge ordinance are written for footing drain water, and roof water is a separate question for Engineering.

Cheap as they are, above-ground extensions still have to reach far enough. EPA's Indoor airPLUS specification carries downspouts to sloping ground at least 5 feet from the foundation, or to an underground catchment at least 10 feet away. Farmington Hills' own 5-foot roof drain rule exempts one- and two-family homes, but it does apply where a house once had roof water piped into the sanitary sewer: those owners must install splash blocks and conductors carrying the water at least 5 feet out. A hinged extension that flips up for mowing beats one that gets left in the garage.