Backup after heavy snowfall melts

Basement drain surging as heavy snow melts on roof

Quick Answer:

If your basement drain is surging while you clear melting snow from the roof, runoff is likely overwhelming part of the drainage system. Start by making sure roof drains, gutters, and scuppers are clear and that downspouts are directing water away from the foundation. Test the sump pump with a controlled roof-level hose test to confirm it can handle the flow, and check for ice dams that may be redirecting water. This situation is a common cause of Backup after snowmelt.

Why This Happens

Heavy snow on the roof holds a lot of water. When it melts quickly, several things can happen at once:

  • Gutters, scuppers, or roof drains clogged with ice and debris can’t accept the volume, so water overflows toward the house.
  • Downspouts without extensions dump meltwater at the foundation instead of away from it.
  • Ice dams force meltwater under shingles or into drainage paths it doesn’t normally use, sending extra water toward low points like basements.
  • If the sump pump or drainage system is already marginal, the sudden surge can exceed capacity and cause the basement drain to surge or back up.

Step-by-Step What to Do

1. Clear roof drains, gutters, and scuppers

  • Remove visible ice and debris from gutters and scuppers so meltwater can flow freely. Do not stand on an icy roof to do this.
  • From a stable ladder or from the ground with a pole tool, clear downspout inlets at the gutter and any scuppers on parapet walls.
  • If ice blocks a gutter, do not hack at it. Consider hiring a pro to remove ice safely.

2. Confirm downspout extensions and direct water away

  • Make sure each downspout has an extension that carries water several feet from the foundation. If missing, temporarily attach a flexible extension or route flow to a safe place on your yard.
  • Avoid sending water into neighbors’ yards, sidewalks, or roads when re-routing runoff.

3. Test sump pump capacity with a controlled roof-level hose test

  • Set up a controlled test that simulates roof runoff: run a garden hose into the gutter or onto the roof edge where runoff would enter the gutter. Only do this if you can work safely—no climbing on icy roofs and use a stable ladder with a helper.
  • Start with a moderate flow and watch the sump pump cycle and the sump pit water level. Note how long the pump runs and whether it keeps up without running continuously.
  • If the pump runs nonstop, trips the breaker, or doesn’t keep the pit level down, the system may not be able to handle heavy melt and needs attention.
  • After the test, restore normal gutter/downspout connections and remove temporary extensions.

4. Inspect for ice dams and redirected meltwater

  • Look along roof edges and inside gutters for ice dams that hold water back and force it under shingles or toward scuppers.
  • If you suspect ice dams are sending extra water to vulnerable areas, consider professional roof/ice-dam removal or installing preventative measures like heated roof cables (installed by a pro).

5. Monitor basement drains and cleanouts

  • Check basement floor drains, cleanouts, and the sump pit regularly during the melt. Keep the sump pit cover in place to reduce debris entering the pump.
  • If you see sewage or persistent backflow, stop using water in the house to reduce flow into the drainage system and call for help if needed.

If you want more background on similar problems after a thaw, see Drain floods after thaw.

What Not to Do

  • Do not shovel snow off the roof toward the foundation. Piling roof snow at the house concentrates meltwater against the foundation.
  • Do not create trenches or channels that deliberately route meltwater to the house.
  • Do not use temporary fixes that move water onto neighboring properties, sidewalks, or streets.
  • Do not delay calling a professional if large snowmelt events regularly trigger backups or your pump cannot keep up—this is not a problem to ignore.

When to Call a Professional

  • Repeated backups during melt events or any time you see sewage backing up into the house.
  • The sump pump fails the controlled test, runs continuously, trips breakers, or you notice unusual noises or overheating.
  • Large ice dams that require roof or gutter work you cannot do safely.
  • Evidence of foundation seepage or structural concerns from excess water near the house.

Safety Notes

  • Avoid working on roofs or ladders when surfaces are icy. Falls are the top risk in these situations.
  • Turn off power to the sump pump only if you know how and can safely work on electrical components; otherwise, leave testing and repairs to a licensed technician.
  • Never redirect wastewater into storm drains, streets, or other properties. Follow local rules and common-sense drainage practices.
  • If you smell gas, see significant electrical arcing, or suspect structural damage, evacuate and call emergency services or qualified professionals right away.

Common Homeowner Questions

  • Why is my basement drain only surging during roof snow melt? Rapid roof melt can overwhelm gutters, downspouts, or the sump pump, sending an unusual volume of surface water to low points like basement drains.
  • Can I test the pump using a garden hose? Yes—use a controlled roof-level hose test to simulate roof runoff, but only if you can do it safely from a stable ladder or the ground; otherwise wait for a pro.
  • Will moving snow piles away from the foundation help? Yes. Keep snow piles and meltwater at least several feet from the foundation and ensure downspout extensions carry water farther out.

More in this topic

For more related fixes and similar symptoms, see Basement Drain Backs Up Only After Rain.

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