Sump Pumps - Bob Vila. "A secondary pump installed right next to the first is a good idea, especially if your basement has been converted to living space. If your primary pump fails or is overwhelmed, the back-up pump automatically takes over. For extra insurance, when the power goes out, as in a storm, a battery-powered back-up pump can cont pumping for up to 2 days... Combo packs exist w/2 or 3 pumps. Or install a water alarm and keep a spare pump."
One of the most frequently asked questions in the reef aquarium hobby is "What is a sump?" Much of this confusion stems from the synonymous use of the words sump, wet/dry filter and refugium. Technically all three are sumps by definition, which simply means a reservoir or container of water. Check out this diagram to find out the differences and similarities of sumps, refugiums and wet/dry filters.