Why does a sump pump fail during the exact weather you need it?
A pump works hardest during the wet months, which is the season that wears it out. After that, the next heavy rain or melt is the load that breaks it. Nothing about water runs on any other schedule.
Replacing a pump before it fails takes deliberation, because a ten-year-old pump that has not failed yet might still have years left. But a ten-year-old pump is overdue, and the inexpensive response is to have a conversation with a plumber in August, before the autumn rains, rather than at 2 a.m. in October.
Test a pump quarterly by lifting the float and listening for it to start and stop. If it does not move, or hums without pumping, it is a sign that the next hard rain will overload it. If the motor does not start at all, the answer is obvious.
How do I prevent the next pump failure?
You cannot, quite, but you can make sure the cellar does not flood when it happens. A second defence, installed alongside a new pump, is what turns a pump failure into an inconvenience rather than a disaster.
The simple version is a floor drain next to the pit, open and clear. Water overflowing from the pit goes to the drain instead of onto the floor, and the room dries faster when the pump is replaced.
A more complete version adds a check valve on the discharge so the water cannot back up into the pit, a sump alarm that calls your phone when the pit gets full, and a backup pump either running on a battery or connected to a portable generator. Ask a plumber which of these is realistic for your house and your pocket, and do it while the cellar is open.
Does a standard homeowner policy cover pump failure?
Most homeowner policies explicitly exclude water from sump or ejector pump failure unless a specific endorsement has been added. It is the same pattern as flood and sewage backup, and the only way to know yours is to read the policy or ask your agent plainly.
It is worth checking before the rain, because the endorsement is routine to add and costs a modest premium. If the loss is not covered, the restoration crew's bill is yours alone, which is a reason to think about prevention as well as response.
Keep a drying log and photographs if you do have water from a pump failure. The evidence is what supports a claim, and the water damage insurance guide covers the general pattern.
What should I do while waiting for a crew?
Move what you can reach from the stairs and get it up off the floor. Photograph the cellar before you move things around. Then step back and call.
Do not go down into the cellar and do not run a household extension lead across wet ground. Do not try to lift the pump out of the pit or pull its plug from underwater. The water in a sump pit has been underground and is not a serious health hazard, which makes it different from a sewer backup, but it is still not something to wade through without equipment.
Check the power: is the breaker still on, is the outlet receiving power, has the GFCI outlet reset itself if one is in the circuit. If the pump was not plugged in at all this is the moment you find that out, which happens.