# Gutters Overflowing in Heavy Rain: Clogged or Not? > A gutter that spills in a downpour is plugged at the downspout, holding water in a low spot, or too small for its roof. How to tell which from the ground. Page: https://fannonpropertyservices.com/guides/gutters-overflowing-in-heavy-rain/ Last changed: 2026-10-30 --- # Why gutters overflow in heavy rain. A plug where the gutter meets the downspout, a run that no longer slopes, or a gutter the roof has outgrown. - Insured - Locally owned - Free estimates ![A cleaned gutter along a metal roof](https://fannonpropertyservices.com/assets/own/gutters-tall.webp) ## Three ways a gutter spills. 1. ![Drawing of a gutter cut open, leaves jammed where it meets the downspout and water spilling over the far end](https://fannonpropertyservices.com/assets/drawn/go-outlet-clog.svg) **One end spills: a plugged outlet.** Leaves jam the outlet and the elbow, so the run fills. In rain the foot of the downspout stays quiet. 2. ![Drawing of a gutter with a low stretch in the middle of its run, water standing in the dip and dripping over its lip](https://fannonpropertyservices.com/assets/drawn/go-sag.svg) **The middle spills: no slope.** Gutters should fall at least 1/16 inch per foot toward the downspout. A stretch that does not will hold water. 3. ![Drawing of a wide roof in heavy rain pouring into a narrow gutter, with water sheeting over its front](https://fannonpropertyservices.com/assets/drawn/go-small-gutter.svg) **Every edge spills: too small.** A clean gutter that still sheets over may be short of downspouts: one every 20 to 50 feet. ### Why is my gutter overflowing when it rains hard? Start at the outlet: when leaves plug the opening into the downspout, the run cannot drain and spills. Next is slope: gutters should fall at least 1/16 inch per foot. If the gutter is clean and sloped, it may be undersized: one downspout every 20 to 50 feet, says the Department of Energy's building guide. We clean gutters around Annapolis. Sources: NC State Extension, West Virginia University Extension, Building America Solution Center, U.S. Geological Survey and NOAA. Checked on 11 October 2026. ## What a storm asks of a gutter 623 gallons run off every 1,000 square feet of roof in 1 inch of rain. *Drawing of a 1,000 square foot roof seen from above in 1 inch of rain, with an arrow to a bucket holding 623 gallons* - **4.44 in** of rain falls at BWI in a normal September, the wettest fall month there. [Gutter cleaning](https://fannonpropertyservices.com/gutters/) [What clogged gutters cause](https://fannonpropertyservices.com/guides/what-happens-if-gutters-are-clogged/) [Where downspouts should drain](https://fannonpropertyservices.com/guides/where-should-downspouts-drain/) ## Questions about overflowing gutters ### Why does my gutter overflow when it is not clogged? It may be too small for the roof above it. For areas with high winds and heavy rain, the Atlantic seaboard among them, the Department of Energy's Building America guide says to increase gutter and downspout capacity to take heavy rain and large roof areas. A gutter that holds water between rains has a slope problem instead. ### Why is water dripping behind the gutter? Rain is running off the roof edge behind the gutter instead of into it. NC State Extension says drip edge flashing should be installed at the roof edge: it sends the water into the gutter and keeps it off the fascia board. Fitting one is roofing work, not cleaning. ### How many downspouts does a house need? Enough to give 1 square inch of downspout opening for every 100 square feet of roof, by the Department of Energy's Building America guide, which also sets how far apart they sit along the gutter. A 1,500 square foot roof, by that rule, wants 15 square inches of opening shared between its downspouts. ### Should a gutter hold standing water after the rain stops? No. A gutter that slopes toward its downspout empties itself. Water still standing a day later means the run has lost its slope or the outlet is plugged. ### How do I tell if the downspout itself is blocked? Watch the bottom of it in rain, or while the gutter is flushed with a hose. West Virginia University Extension's gutter guide says to start at the low end by the outlet and keep an eye on the drain spout: water that does not flow freely out of it means a blockage inside the pipe or its elbows. Sources and further reading - [Building America gutter sizing](https://basc.pnnl.gov/resource-guides/gutters-and-downspouts) - [USGS rainfall volumes](https://www.usgs.gov/water-science-school/science/rain-and-precipitation) ## Get a free estimate. Say where the gutter spills and we will quote a cleaning. Estimates are free in Anne Arundel County and on Kent Island. [Call (443) 223-8643](tel:+14432238643) [How estimates work](https://fannonpropertyservices.com/estimates/) [Towns we cover](https://fannonpropertyservices.com/service-area/) ![Illustration of a Fannon Property Services Ford F-150 pickup in navy and blue](https://fannonpropertyservices.com/assets/gen/truck-cutout.webp)