In Metro Vancouver the heaviest rain often arrives with the wind that takes the power out. That is the exact moment a mains-only sump pump stops working.
A sump pump installation is only as good as the parts around it: a check valve that actually holds, a discharge line that runs somewhere sensible and will not freeze, a float with clear travel, and a pit that is not undersized for the inflow.
And then there is power. A mains-only pump in a region where heavy rain and power cuts arrive together is a system with an obvious single point of failure. A battery backup removes it.
Most calls turn up something else worth looking at. Here is what else we handle.
New pump, battery backup, or both. Quoted in writing, fitted before the rain.