How Do You Keep a Sump Pump Discharge Line From Freezing?
You keep a sump pump discharge line from freezing by making sure no water sits in it between pump cycles. That means sloping the outside pipe so it drains, keeping the exit open and clear of snow, and adding a relief fitting that gives water a way out if the buried section ices over. A frozen sump pump line matters in Western Pennsylvania because NOAA's 1991 to 2020 normals put the January mean temperature at Pittsburgh International Airport at 28.8 F, below freezing for the whole month on average, with 44.1 inches of snow a year.
Pump makers already treat ice as a known failure. Liberty Pumps' installation manual for its 230, 240, and 450 series submersible sump pumps tells owners to check the discharge line for foreign material, "including ice if the discharge line passes through or into cold areas," and it says not to reduce the discharge pipe below 1-1/4 inches. This post covers why lines freeze, the signs, how to prevent it, what to avoid, and what to do if yours is frozen right now.
Why Does a Sump Pump Discharge Line Freeze?
A sump pump discharge line is the pipe that carries water from the pump in your basement pit out through the wall and away from the house. The pump pushes water out in short bursts. Between bursts, whatever water is left in the outdoor section just sits there, and in a Pittsburgh January that standing water turns to ice.
Most freeze-ups trace back to a few setups:
Low spots or sags. A pipe that dips, even slightly, holds a puddle after every cycle. Each cycle adds a little more ice until the pipe closes.
Long exposed runs. Pipe lying on top of the ground, or hung along a foundation wall, has no protection from wind and cold air.
Buried too shallow. A line run just under the surface sits in soil that freezes. Water trapped in it has nowhere to go.
A blocked exit. Snow drifts, ice from a dripping roof, leaves, or a crushed end cap can stop water at the outlet. Once it backs up, it freezes from the outlet back toward the house.
What Are the Signs Your Discharge Line Is Frozen?
The first clue is usually sound. You hear the pump running, but the water level in the pit does not drop, or it drops very slowly. You may also notice it running without shutting off. If so, our guide to a sump pump that runs constantly walks through other causes to rule out.
Other signs:
A high water alarm sounds. Here is what a sump pump alarm usually means.
Water rises to the rim of the pit or spills onto the basement floor.
The outdoor end of the pipe is dry, capped with ice, or buried in snow during a thaw or rain.
Water leaks at a joint or fitting inside the basement, pushed out by pressure with no place to go.
North Dakota State University Extension warns that a pump pushing against a frozen or plugged discharge usually will not burn up, but it can overheat. Submersible pumps rely on the surrounding water for cooling.
How Do You Prevent a Frozen Sump Pump Line?
A line that empties itself after every cycle has nothing left in it to freeze.
Slope the line so it drains
Check the outdoor run from the wall to the outlet. It should fall steadily away from the house with no dips. PumpSpy's winter guidance tells homeowners to confirm the discharge line "slopes downward to prevent water from pooling and freezing." If you can see sags in a surface pipe, re-support it. If a buried section holds water, it may need to be dug up and re-laid.
Use the right pipe size, and a bigger exit
Do not neck the line down. Zoeller's instructions for its residential 1073 and 1075 pumps show a 1-1/2 inch discharge pipe, and Zoeller's battery backup instructions say not to use a discharge pipe smaller than the pump discharge. Outside, the line often steps up to a larger 3- or 4-inch drain pipe, and freeze relief fittings are sold in those sizes for that transition. A wider pipe gives water more room to move and takes longer to close with ice.
Add a freeze relief fitting
A freeze relief fitting, sometimes sold as a freeze guard or ice guard, sits outside where the pump line connects to the larger buried pipe. ELK describes its Freeze Relief as a transition between 1-1/2 inch sump pump PVC and 4 inch SDR 35 pipe that "allows excess water and pressure to escape from the discharge line system." PumpSpy says its Freeze Drain lets water escape through perforations when the line clogs, giving it "a secondary escape route." If the buried pipe freezes, water spills onto the ground near the fitting instead of backing into your basement.
These fittings do not stop freezing. They keep a frozen buried line from taking the pump down with it. Place the fitting so the water it releases flows away from the foundation.
Keep the outlet clear and far from the house
After every snowfall, check the end of the pipe. A shovel's worth of snow is all it takes to cap it. NDSU Extension says sump water should preferably be discharged at least 20 feet from the house. For comparison, the Department of Energy's Building America Solution Center says downspouts should discharge at least 5 feet from the foundation, or underground at least 10 feet away.
Insulating exposed pipe helps where a run cannot be buried or sloped, but it only slows heat loss. It will not save a line that holds water.
What Should You Not Do With a Frozen Discharge Line?
Some quick fixes cause bigger problems than the ice.
Skip open flames. The American Red Cross says never to thaw a frozen pipe with a blowtorch, kerosene or propane heater, charcoal stove, or any other open flame device.
Do not tie the pump into a sanitary drain, laundry tub or floor drain to get through the winter. 3 Rivers Wet Weather, a Pittsburgh-area group focused on sewer overflows, says roof drains and sump pumps attached to the sanitary sewer are illegal connections, and that "stormwater should never be connected into a sanitary system designed to carry only wastewater." Check with your municipality before changing where the pump drains.
Do not unplug the pump and walk away. If groundwater keeps rising, the pit will overflow. And do not leave a cut or disconnected pipe spraying water against the foundation, since that water can find its way right back to the pit.
What Should You Do If Your Sump Pump Line Is Frozen Right Now?
Find the blockage. Look at the outlet first. Clear snow and ice from the end, and check whether water starts flowing.
Give the water a temporary path. If the frozen section is outside, disconnect the line at a joint just outside the house, or at a union inside if you have one, and attach a hose or short temporary pipe that carries water well away from the foundation. Keep it on a steady downhill run.
Thaw the frozen section with safe heat. The Red Cross lists an electric heating pad, an electric hair dryer, a portable space heater kept away from anything flammable, or towels soaked in hot water.
Watch the pump. Pour a bucket of water into the pit and make sure the pump starts, empties the pit, and shuts off. NDSU Extension suggests watching it turn on and off at least twice.
Fix the cause once it thaws. A line that froze once will freeze again unless the slope, size, or outlet changes.
If the frozen section is buried and you cannot reach it, or water is already coming over the pit, call for help. Our post on protecting your basement from winter water damage covers other cold weather checks.
Is a Frozen Line a Sign of a Bigger Drainage Problem?
Sometimes. A pump that runs often all winter sends more water through the line, which gives ice more chances to build and wears the pump. If yours is older and working hard, read our notes on how often a sump pump should be replaced.
A fall checkup catches a sagging line or clogged outlet before the first freeze, and our sump pump maintenance tips for Western Pennsylvania include a simple checklist. If water reaches the pit faster than the system can handle, the fix may be a larger change to how water is collected, which is part of basement waterproofing.
FAQ
Will a frozen sump pump line thaw on its own?
It may during a warm spell, but you should not count on it. While the line is frozen, the pump has nowhere to send water, so the pit can overflow before the weather turns.
Should I bury my sump pump discharge line?
Burying protects the pipe from cold air, but a buried line must still drain completely and end somewhere water can escape. Pair any buried run with a freeze relief fitting so a frozen section cannot back water into the basement.
Does a check valve cause the discharge line to freeze?
The check valve holds water in the vertical pipe inside the basement, which is usually in a heated space. The outdoor section should drain toward the outlet, so water sitting outside points to a slope or outlet problem.
Is sump pump freeze protection worth it for a Pittsburgh area home?
For most homes with an outdoor discharge, yes. NOAA's January normal of 28.8 F at Pittsburgh International Airport means freezing weather is routine, and one blocked line can put water on the basement floor.
Can I run the discharge into my laundry sink for the winter?
Not without checking local rules. 3 Rivers Wet Weather describes sump pumps attached to the sanitary sewer as illegal connections, and a laundry sink drains to the sanitary sewer.
Talk to A Better Choice, Inc. About Winter Sump Problems
A Better Choice, Inc. has served homeowners in the Greater Pittsburgh area since 1996 and fixes wet basements across Westmoreland, Allegheny, Butler, and neighboring counties. If your sump pump line keeps freezing or your pit keeps filling, the family- and veteran-owned team can take a look during a free inspection and explain your options, including basement waterproofing in Pittsburgh.
Visit A Better Choice, Inc. or call 1-800-343-2357 today. Contact us for more information.
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