Underground Downspout Drains: Pros, Cons and Winter Freezing

What is an underground downspout drain?

An underground downspout drain connects the bottom of a downspout to a pipe buried in the yard. The pipe runs downhill to an outlet, where the water returns to the surface or soaks into the ground.

Common outlets include an open end on a slope (called daylighting), a pop-up emitter that opens when water flows and closes when it stops, and a buried dry well that lets water seep into the soil. Above-ground extensions and splash blocks do the same job with no digging.

Pros of burying your downspouts

The biggest advantage is distance. A buried pipe can carry water much farther from the foundation than a short extension, which protects basements and crawl spaces.

Buried drains also keep lawns and walkways clear. There are no extensions to trip over, mow around or knock loose, and you choose where the water goes.

Cons and common problems

Underground drains are out of sight, so problems often go unnoticed until water backs up. These are the issues that show up most often.

• Freezing in low spots, elbows and shallow sections during cold weather
• Clogs from leaves, shingle granules and debris washed down from the gutters
• Corrugated pipe that traps debris in its ridges and slows the flow
• Crushed or separated pipe under driveways, foot traffic or settling soil
• Buried or blocked outlets under snow, mulch or grass

When any of these stop the flow, water backs up the downspout and overflows the gutter, often right beside the foundation the drain was meant to protect. Our guide to how gutters damage foundations explains why that matters.

Why buried downspouts freeze in Wisconsin

Buried downspouts freeze when water sits in the pipe long enough to turn to ice. That happens where the pipe dips, flattens out or turns, because water collects at those points instead of running through.

Winter snowmelt makes it worse. On a sunny afternoon the roof sheds meltwater into the pipe, and when the temperature drops at night, whatever is still in the line freezes and the ice spreads.

A frozen line has nowhere to send the next melt. Water then backs up into the downspout and gutter, which can freeze there too and add to ice along the roof edge.

How to keep a buried downspout from freezing

Good design matters more than any winter fix. The goal is a pipe that drains completely empty after each rain or thaw.

1. Slope it the whole way. Installers commonly use at least 1/8 to 1/4 inch of fall per foot, with no dips or flat sections.
2. Use smooth-wall pipe. Smooth PVC or similar pipe drains faster and clogs less than corrugated pipe.
3. Keep elbows to a minimum. Every turn slows the water and gives ice a place to start.
4. Daylight the outlet where the grade allows. An open outlet on a slope drains freely, while a pop-up emitter can freeze shut or get buried in snow.
5. Add a diverter. A downspout diverter lets you send water to an above-ground extension during freezing months and back to the buried line in spring.
6. Keep debris out. Clean the gutters in fall, and consider gutter guards so leaves never reach the pipe.

A heat cable run through a known problem spot can keep a channel open, though it adds an electrical cost. Our guide to heated gutters and heat cables explains where cables help.

After each winter thaw, walk the outlets and clear any snow or ice so the next melt has somewhere to go.

Water backing up or spilling at your downspouts? Call (608) 909-9109 for a free on-site inspection.

Installation details that make the difference

A buried drain lasts when it is installed for maintenance as well as flow. Ask for a clean-out where the downspout meets the pipe, so a hose or drain snake can reach a clog without digging.

Send the water far enough from the house that it drains away from the foundation, not back toward it or onto a neighbor's property. Many cities restrict connecting downspouts to sanitary sewers, so check your local rules before tying into anything underground.

Call 811 before any digging. In Wisconsin that reaches Diggers Hotline, which arranges for buried utility lines to be marked at no charge.

Underground drains vs extensions vs rain barrels

Above-ground extensions cost little and are easy to check, but they clutter the yard and get knocked loose. They are also the simplest winter fallback for a buried line.

Rain barrels collect roof water for later use but fill quickly in a heavy storm and need an overflow route, and they must be drained before freezing weather. Our guide to rain barrels and gutters covers setup.

For help deciding where your downspouts should drain in the first place, read our guide to downspout drainage and our guide to gutter drainage solutions.

Signs your underground drain is failing

Watch the downspouts during a heavy rain. Water spraying from downspout joints, overflowing the gutter, or bubbling up at the base of the downspout usually means the buried line is blocked.

A dry outlet during a storm points to a clog or a break upstream. Soggy ground, sinking soil or a small sinkhole along the pipe route often means the pipe has separated or cracked underground.

Getting downspout drainage fixed

Downspout problems are usually part of a bigger drainage picture, so an inspection should cover the gutters, the downspouts, the outlets and the grading together. Buckshot Exteriors is family-owned and has worked on exteriors since 1979, with offices in Madison, WI and Centerville, IA.

Our downspouts page covers downspout work, and our gutters page covers the rest of the system. Call (608) 909-9109 to schedule a free on-site inspection.