Inside: the sump system (checks 1–3)
1. Bucket-test the pump. Pour a full bucket of water into the pit. The pump should start, empty the pit, and stop cleanly — no hesitation, no grinding, no running on after the water is gone. A pump that fails this test in March fails for real in April.
2. Check the float. Make sure the float switch moves freely and nothing in the pit — a cord, debris, the liner wall — can pin it. A jammed float is the most common “pump was fine, basement still flooded” story.
3. Confirm the check valve works. After a pump cycle, water should not rush back down the discharge pipe into the pit. If the pit refills without new inflow, the valve is done — a cheap part that doubles pump wear when it fails.
Outside: where the meltwater goes (checks 4–8)
4. Find the discharge outlet. Follow the sump line to where it exits. It must be clear of snow, ice and leaves, and the water must visibly flow away from the house. A discharge line buried in a snowbank pumps water into a pool beside your own wall.
5. Pull snow back from the foundation. Clear a band of one to two metres around the house, especially the south and west walls, which melt first and fastest. Every cubic metre of packed snow you move is a couple of hundred litres of water that will soak in somewhere else.
6. Empty the window wells. A well packed with snow and frozen leaves is a bucket that empties against your basement window. Dig them out and check the drain at the bottom isn't iced over.
7. Extend the downspouts. Two metres minimum from the wall, discharging onto ground that slopes away. Reattach the extensions that came off with the snow-shovelling — that is most of them.
8. Locate the catch basin. If your street drains to a catch basin near your driveway, clear the ice and debris cap off it. When it's blocked, the whole street's meltwater looks for the next low spot — sometimes that is your lot.
Watching: the melt weeks themselves (checks 9–10)
9. Walk the basement weekly. Flashlight along the wall-floor joint, into corners, behind stored boxes. You are looking for damp arcs, darkened concrete and new white staining — the early, cheap-to-fix signals.
10. Photograph anything damp. A dated photo does two jobs: it shows whether a patch is growing week to week, and it gives whoever diagnoses it (us or anyone else) the pattern instead of a memory.
When to stop watching and call: standing water anywhere, a damp patch that returns to the same spot after every thaw, a sump running around the clock, or a musty smell that doesn't leave with airing. Those four aren't maintenance items — they're symptoms. The assessment is free.
Keep reading: Sump pump maintenance schedule · What the white powder on walls means
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A free assessment covers all ten checks and the parts you cannot see — the drains, the grading and the foundation itself.