You can buy a sump pump that will operate even when the electrical power goes out due to a thunderstorm, major flood, or brownout, for example.

Most of these are intended to be auxiliary pumps. Used in tandem with the primary pump, they kick in if the main pump fails.

One type runs on a rechargeable 12-volt battery. If you get this type, it pays to buy one that has an automatic battery recharger that will keep the battery alive even when it hasn’t been used for months. This charger should be designed so that overcharging the battery is never a problem.

Another type of sump pump backup system is hooked up to the house’s water system and operates by water pressure. If the electrical power goes out, the water-pressure backup takes over.

Whether or not you need a backup really depends on your situation—the likelihood of a power or pump failure and the damage such a failure could cause. Because the backup system doesn’t add much to the price of a sump pump, it is usually worth paying the premium.

In some cases, an inexpensive high-water alarm will suffice. With one of these, the alarm senses rising water and sounds. On the other hand, if you’re going to lie in bed on rainy nights worrying if everything you’ve stored in the basement is under water, a backup may give you more than flood protection—it may give you peace of mind.