Home › Sump pump battery backup

Sump Pump Battery Backup and Water-Powered Backup: Pros, Cons and Costs

Updated November 1, 2026 · General information, not plumbing or electrical advice

Some links on this page are affiliate links. If you buy through them we may earn a commission at no extra cost to you. How we make money.

The short answer: A battery backup is the most popular type, according to Ann Arbor, Michigan. It runs on a deep-cycle battery for roughly 7 to 24 hours (Ann Arbor) and costs less to install. A water-powered backup runs on city water pressure, doesn't need electricity, but uses about 2 gallons of fresh water for every 1 gallon pumped and needs a backflow valve. It isn't an option on well water (Consumer Reports).

Safety first. Sump pumps run on household power in a wet place. Unplug the pump before you handle it, stay out of standing water that is near outlets, a panel or appliances, and hire a licensed electrician or plumber for wiring and plumbing work. Check local codes and permit rules. This safety note is ours, not from a source.

Battery backup

Ann Arbor describes an emergency pump powered by a deep-cycle marine gel cell battery, installed in the pit slightly higher than the main pump. It is plugged into a household outlet so a charger keeps the battery full, and it starts automatically in a power outage. An alarm sounds if the power is out, the pump is running or the battery is low. Battery backup pumps are usually less powerful than the primary, about 10 gallons per minute compared to 30 or 60 for primary pumps.

Pros (Ann Arbor): low maintenance beyond replacing the battery, low up-front cost, easy to install, works if the primary pump fails, and uses the existing discharge piping in most cases.
Cons (Ann Arbor): limited battery life (generally 7 to 24 hours of pumping), batteries must be replaced about every three years, and failures can still occur in the pump or check valve.
Battery tips (NDSU Extension): use a deep-cycle lead-acid battery; the AH rating determines the hours of protection; buy near the maker's maximum, typically around 120 AH; check every six months for charge and corrosion; a standard vehicle battery can be used in an emergency.
Consumer Reports says most models move 800 to 2,000 gallons per hour, and that battery backups are relatively easy for DIYers with basic plumbing knowledge. It recommends a backup pump with a gallon-per-hour rate that matches or exceeds your primary pump's, accounting for vertical lift.

Water-powered backup

Ann Arbor says a water-powered backup uses your pressurized fresh water supply and the Venturi effect to draw water out of the pit. It needs new water pipes from the nearest supply line and a backflow-prevention device (an RPZ valve) so sump water cannot contaminate the public supply.

Pros (Ann Arbor): runs as long as there is water pressure in the house, doesn't rely on electricity, and has simple mechanics.
Cons (Ann Arbor): uses about 2 gallons of fresh water per gallon of sump water; costs more than a battery backup to install; the RPZ valve must be tested by a licensed certified plumber and inspected by the city every 3 years (Ann Arbor's rule); the sump cover may not be radon sealed; and a stuck float could mean a large water bill.
Consumer Reports: these units aren't an option for homeowners using well water, and most require professional installation.

Other options (Ann Arbor)

Option	Good for	Watch out for
High-water alarm	Warning that the pit is rising. Simple alarms can cost as little as $10; sophisticated ones a few hundred dollars.	Many rely on batteries; if the battery fails the alarm doesn't work.
Second pump kept next to the pit	A handy person can usually swap it in a few minutes.	You must be home to make the switch.
Manual-start generator	Can also power other parts of the home. Prices range from a few hundred to several thousand dollars.	You must be home to start it. It doesn't protect against pump failure. Extension-cord connections can be dangerous if not done correctly.
Automatic standby generator	Starts automatically and can power select circuits.	Professional installation, cost, and maintenance twice a year. Needs a permit in many places.
Second primary pump in the pit	Same power as the first; highly reliable if power is available.	Crowded pit, and best practice is its own circuit and a dedicated discharge.

Source: City of Ann Arbor, Michigan, Sump Pump Backup Options.

Which should I choose?

Use the backup checker to see how much risk you have.
Private well? Rule out water-powered (Consumer Reports).
Think about outage length. A battery gives hours; a generator or city-water-powered pump can run longer.
Check permits. Ann Arbor says battery, water-powered and standby generator installs generally need a permit from the local building department.
Get quotes from licensed pros and keep the main pump tested too.

Does your sump pump need a backup?

Answer six quick questions based on the risk factors Ann Arbor, Michigan lists. Get a plain answer and the backup types that fit.

Open the backup checker

Browse battery backup pumps

Common questions

What is the best sump pump backup?

There is no single best one. Ann Arbor calls the battery-powered backup the most popular among homeowners, and lists alarms, second pumps, water-powered backups and generators as other options. Use our backup checker to weigh your risk factors. Consumer Reports says water-powered backups aren't an option for homeowners using well water.

How long does a battery backup sump pump run?

Ann Arbor says generally 7 to 24 hours of pump operation. Consumer Reports says a fully charged battery typically provides 7 to 8 hours of active pumping. NDSU Extension says the battery's amp-hour (AH) rating determines the hours of protection.

What kind of battery do I need?

NDSU Extension recommends a deep-cycle lead-acid battery and says to buy one with an AH rating near the maximum the pump maker recommends, typically around 120 AH. It also says to check the battery every six months for adequate charge and corrosion.

Do water-powered backups use a lot of water?

Ann Arbor says they use about 2 gallons of pressurized fresh water to pump out 1 gallon of sump water, and the use shows up on your water bill. If the float sticks in the on position, the result could be a large water bill.

Related guides

Sources

Free printable: Sump Pump Fall Check

A ten-minute test before the wet season. Download the one-page PDF now, or get it by email along with a short series of five helpful emails.

Download the PDF