Best battery backup sump pump, and how long each one runs
Buy the Basement Watchdog Special CONNECT (BWSP) if you already have a working sump pump. It is $279 at Amazon, plus $209 for the battery it needs. It pumps 1,850 gallons an hour at a 10-foot lift. One charge moves about 7,100 to 8,900 gallons: 3.8 to 4.8 hours of nonstop pumping, or days when water only trickles in.
No backup keeps a basement dry in every storm. A pump falls behind when water comes in faster than it can pump, and every battery runs down. See the numbers
The Amazon links on this page are affiliate links: if you buy through one we may earn a commission, at no extra cost to you. It does not change which units are picked. How that works.
Our pick for each job
- You have a working sump pump
Basement Watchdog Special CONNECT (BWSP)
plus the BW-27AGM battery ($209)$279 at Amazon - Your main pump is old too: replace both at once
Basement Watchdog Big Combo CONNECT (CITS-50)
plus the BW-27AGM battery ($209)$469 at Amazon - No room for a second pump in the pit
PumpSpy 2000 W battery backup (BU-2000)
plus the PS1275 battery ($200)$300 at Amazon - City water, and no battery to look after
Liberty SumpJet SJ10 (water-powered)$231 at Amazon
Each pick follows a stated rule: the backup pump that moves the most water at a 10-foot lift, with a runtime the maker publishes. We did not test these. Commission never picks.
How long a battery backup sump pump runs
A backup pump only runs while water comes in. So the useful number is how many gallons one charge can move. Divide that by how fast water enters your pit, and you get the hours. Each range runs from 80% of the maker’s figure (an older battery: plan for this) up to the maker’s figure (a new battery).
| System | Gal/hour at 10 ft | Gallons per charge | Nonstop pumping | Pump cycles per charge |
|---|---|---|---|---|
| Basement Watchdog BWSP Backup pump (keeps your pump) | 1,8501 | 7,100–8,9002 | 3.8–4.8 h | 800–1,000 |
| Wayne ESP25N Backup pump (keeps your pump) | 1,6808 | 8,000–10,0009 | 4.8–6 h | 900–1,100 |
| Zoeller Aquanot 508 Backup pump (keeps your pump) | 1,80012 | 7,900–9,90012 | 4.4–5.5 h | 900–1,100 |
| Basement Watchdog CITS-50 New main pump + backup | 1,8503 | 8,900–11,1004 | 4.8–6 h | 1,000–1,300 |
| Basement Watchdog CITE-33 New main pump + backup | 1,0005 | 3,800–4,8006 | 3.8–4.8 h | 400–500 |
| Wayne WSS30VN New main pump + backup | not published | 8,000–10,00010 | not published | 900–1,100 |
Gallons per charge = the maker’s nonstop hours × its gallons per hour at a 10-foot lift, or the maker’s own gallons figure. Pump cycles assume an 18-inch pit emptied 8 inches each time (about 8.8 gallons). Wayne's listing says 'up to 10,000 gallons of water per hour on a single battery charge'; the pump's own maximum is 2,900 gallons an hour, so we read it as 10,000 gallons per charge, the figure Wayne gives for the WSS30VN on the same battery. Wayne does not publish the WSS30VN backup’s flow at 10 feet, so we cannot say when it falls behind. Zoeller warns that some makers rate 12-volt pumps on a test that reads 40% to 80% high12, which is one more reason to plan on the low end.
How long one charge lasts at your inflow
The faster water comes in, the more the pump runs and the sooner the battery is flat. Hours below are for one charge, from an older battery to a new one. “Falls behind” means the water comes in faster than the pump moves it at a 10-foot lift.
| Water coming in at | 1 gal/min | 5 gal/min | 15 gal/min | 30 gal/min |
|---|---|---|---|---|
| Basement Watchdog BWSP | 4.9–6.2 days | 24–30 h | 7.9–9.9 h | 3.9–4.9 h |
| Wayne ESP25N | 5.6–6.9 days | 27–33 h | 8.9–11 h | falls behind |
| Zoeller Aquanot 508 | 5.5–6.9 days | 26–33 h | 8.8–11 h | 4.4–5.5 h |
| Basement Watchdog CITS-50 | 6.2–7.7 days | 30–37 h | 9.9–12 h | 4.9–6.2 h |
| Basement Watchdog CITE-33 | 2.7–3.3 days | 13–16 h | 4.3–5.3 h | falls behind |
| Wayne WSS30VN | 5.6–6.9 days | 27–33 h | 8.9–11 h | 4.4–5.6 h |
How fast is water coming into your pit?
Watch the pit during a hard rain. When the main pump shuts off, time how long the water takes to rise one inch. An 18-inch pit holds about 1.1 gallons per inch; a 24-inch pit about 2.0. Divide by the minutes. Example: an 18-inch pit that rises an inch in 30 seconds is taking on about 2.2 gallons a minute.
Under 1 gallon a minute, any unit here lasts days. At 15 gallons a minute, one charge lasts hours, and a second battery or a water-powered backup starts to make sense. Basement Watchdog says two of its batteries, linked, double the runtime on the BWSP and CITS-507.
Battery backup pump, power station or water-powered?
Four ways to keep a sump pump going in an outage. Hours are for one charge, nonstop.
| Type | What it runs | Turns on by itself | Nonstop pumping on one charge | Good to know |
|---|---|---|---|---|
| Battery backup pump e.g. Basement Watchdog BWSP | A second, 12-volt pump in the same pit | Yes, on its own float | 3.8–4.8 h | Moves less water per hour than your main pump. Only pumps. |
| Battery box for your own pump e.g. PumpSpy 2000 W | Your main pump, from a battery | Yes, it switches to battery when the power fails14 | 0.4–1.1 h on a 75 Ah battery | Your main pump draws far more power than a 12-volt pump, so the battery runs down fast. |
| Portable power station e.g. EcoFlow DELTA 2 Max | Your main pump, plus the fridge, Wi-Fi or a CPAP | Only if the pump stays plugged into it. How | 1.2–2.5 h | Runs more than the pump, and you can recharge it from solar. |
| Water-powered backup e.g. Liberty SumpJet SJ10 | City water pressure pushes the sump water out | Yes, on its own float16 | No battery: runs while city water pressure holds | 558–912 gal/hour at a 12-foot lift, on 40 to 60 psi. Uses your city water to do it. Not for homes on a well. |
A battery box that runs your own pump, like the PumpSpy 2000 W battery backup (BU-2000), sits beside the pit and powers your main pump when the grid drops. We size a sump pump at 700–1,500 watts while it runs, so a 75 Ah battery lasts about 0.4–1.1 hours of nonstop pumping. It is the answer when there is no room for a second pump.
If your main pump is old too, buy the Basement Watchdog Big Combo CONNECT (CITS-50). It is $469 at Amazon, plus $209 for the battery it needs. It comes with a 1/2 HP main pump and the same 1,850 gallon-an-hour backup, already plumbed together. Basement Watchdog rates it at about 8,900 to 11,100 gallons per charge.
Water-powered backups need city water at 20 psi or more and keep going as long as the pressure holds. They use your water to do it. Liberty lists a backflow check valve in its SumpJet16. Your local code may require more, so ask a plumber.
When a power station makes more sense
A power station runs your main pump for fewer hours on one charge (the EcoFlow DELTA 2 Max: about 1.2–2.5 hours nonstop). It earns its price when the outage is about more than the basement: it can run the fridge, Wi-Fi and a CPAP, and it recharges from solar panels. Buy one if you need those too, or if your pit has no room for a second pump. See the best power stations for a sump pump.
Every system compared
Each row is one product Amazon sells, matched by the maker’s model number. Flows are the maker’s own. Where an Amazon listing prints a higher flow than the maker’s page, we use the maker’s.
| System | Gallons per hour (maker) | Battery | Alerts | Warranty | Amazon |
|---|---|---|---|---|---|
| Basement Watchdog Special CONNECT (BWSP) Backup pump (keeps your pump) | 2,600 at 0 ft; 1,850 at 10 ft1 | Not included. Uses the BW-27AGM battery (two double the runtime) | Alarm and lights on the controller; Wi-Fi alerts with the BW-WiFi2 module (sold separately) | 2 years; up to 4 with the maker's AGM battery and online registration | $279 at Amazon |
 Wayne ESP25NBackup pump (keeps your pump) | 2,900 at 0 ft; 1,680 at 10 ft8 | Not included. Uses the WSB1275 battery | LED display and audible alarm on the battery case | 2 years | $300 at Amazon |
 Zoeller Aquanot Spin 508 (508-0005)Backup pump (keeps your pump) | 1,800 at 10 ft12 | Not included. Zoeller's minimum: a group 27 deep-cycle battery with 175 minutes reserve capacity | Alerts for power outage, high water and switch obstruction; monitors itself | not checked | $449 at Amazon |
| Basement Watchdog Big Combo CONNECT (CITS-50) New main pump + backup | 2,600 at 0 ft; 1,850 at 10 ft3 1/2 HP main pump, 3,540 gal/hour at 10 ft | Not included. Uses the BW-27AGM battery (two double the runtime) | Alarm and lights; Wi-Fi alerts with the BW-WiFi2 module (sold separately) | 2 years; up to 4 with the maker's AGM battery and online registration | $469 at Amazon |
 Basement Watchdog Combo (CITE-33)New main pump + backup | 2,000 at 0 ft; 1,000 at 10 ft5 1/3 HP main pump, 3,100 gal/hour at 10 ft | Not included. Uses the BW-27AGM battery | Alarm and lights on the controller | 2 years; up to 4 with the maker's AGM battery and online registration | $379 at Amazon |
| Wayne WSS30VN New main pump + backup | 10-foot flow not published 1/2 HP main pump | Not included. Uses the WSB1275 battery | not stated | 3 years | Not linked: Title does not contain the model 'WSS30VN' as a whole word. |
| PumpSpy 2000 W battery backup (BU-2000) Battery box that runs your own pump | Your own pump’s flow (up to 2,000 W, 16.6 A)14 | Not included. Uses the PS1275 battery | not stated | not checked | $300 at Amazon |
| Liberty SumpJet SJ10 (water-powered) Water-powered, no battery | 558–912 at 12 ft, on 40–60 psi city water16 | None needed | No alarm on the SJ10; Liberty's SJ10A adds one | not checked | $231 at Amazon |
Prices checked October 14, 2026; we keep no price history.
Which battery to buy
Buy the battery the maker tested with. It is the one its runtime figure is based on. Basement Watchdog rates its systems on its BW-27AGM; Wayne on its 75 Ah WSB1275; Zoeller asks for at least a group 27 deep-cycle battery with 175 minutes of reserve capacity12. Basement Watchdog says to replace its battery once it is more than five years old2.
| Battery | Amp-hours | Made for | Amazon |
|---|---|---|---|
 Basement Watchdog BW-27AGM battery | Not published by the maker7 | Basement Watchdog BWSP, Basement Watchdog CITS-50, Basement Watchdog CITE-33 | $209 at Amazon |
 Wayne WSB1275 battery (12 V, 75 Ah) | 75 Ah11 | Wayne ESP25N, Wayne WSS30VN | $277 at Amazon |
 PumpSpy PS1275 battery (12 V, 75 Ah AGM) | 75 Ah15 | PumpSpy 2000 W | $200 at Amazon |
Not on this page, and why
- Liberty Pumps 441: Liberty's flow at 10 feet and runtime were not in any Liberty document we could read, and the only Amazon seller was a reseller with 3 left.
- Superior Pump 92910: One unit left from a reseller, and Superior publishes a maximum flow only, not a 10-foot figure.
- Basement Watchdog Big Dog CONNECT (BWD12-120C): Showed as currently unavailable on Amazon on October 13, 2026.
- No-name 'sump pump battery backup' inverters (Sunivora, VEVOR, UPS-TK and others): No maker manual or runtime figure we could check, and no long owner history.
Recall check
No recall names any model on this page. That is the result of one search on one date, not a safety clearance. We searched all 10,047 recalls in the CPSC database on October 13, 2026. The closest results were other products:
- Zoeller septic pumps with a 20-foot cord (2007, recall 07104): a different Zoeller product, not the Aquanot 508.
- Wayne WaterBUG GLOW multi-use pumps (Scott Fetzer, 2021, recall 21124): a utility pump, not the ESP25N or WSS30VN.
- Utilitech, Do It and Star Water sump pumps (2020, recall 20069): other brands.
Questions people ask
How long will a battery backup sump pump run?
It depends on how fast water comes in. The Basement Watchdog Special CONNECT (BWSP) moves about 7,100 to 8,900 gallons on one charge. Running nonstop, that is 3.8 to 4.8 hours. With water coming in at 5 gallons a minute, it lasts about 24 to 30 hours, because the pump rests between cycles. The low end is for an older battery.
Do battery backup sump pumps come with a battery?
Not the ones on this page. Every one is sold without its battery, so add one to the cart. Each maker names the battery it tested with; the table above lists it.
Can I add a battery backup to my existing sump pump?
Yes. A backup-only pump sits in the same pit as your main pump and turns on if the water rises past it. Your pit needs room for both, and the discharge pipe has to be set up for two pumps. A plumber can tell you if yours works; we do not give install steps.
Is a power station better than a battery backup sump pump?
Not for the pump alone. A backup pump turns on by itself and pumps for more hours on one charge. A power station like the EcoFlow DELTA 2 Max makes sense when you also need the fridge, Wi-Fi or a CPAP during the outage. It runs a typical sump pump nonstop for about 1.2 to 2.5 hours.
How long do sump pump backup batteries last?
Basement Watchdog says to replace its battery once it is more than five years old. A battery holds less charge as it ages, which is why our runtime tables show a low end at 80% of the maker's figure.
Does a water-powered backup sump pump need electricity?
No. The Liberty SumpJet SJ10 (water-powered) runs on city water pressure. Liberty rates it from 20 psi up; at 40 psi it moves 558 gallons an hour at a 12-foot lift. It will not work if your water comes from a well, because the well pump stops when the power does. Local code may require a backflow preventer, so ask a plumber.
Sources
- Basement Watchdog: Special CONNECT (BWSP) product page, read October 13, 2026
- Basement Watchdog: BWSP product manual (04-17-23), read October 13, 2026
- Basement Watchdog: Big Combo CONNECT (CITS-50) product page, read October 13, 2026
- Basement Watchdog: CITS-50 U.S. manual (06-17-25), read October 13, 2026
- Basement Watchdog: Combo (CITE-33) product page, read October 13, 2026
- Basement Watchdog: CITE-33 U.S. manual (05-15-25), read October 13, 2026
- Basement Watchdog: maintenance-free AGM battery (BW-27AGM) page, read October 13, 2026
- Wayne: ESP25-N operating instructions and parts manual (600001-001 B, 08/18), read October 13, 2026
- Wayne ESP25N listing on Amazon (sold by Amazon.com), read October 13, 2026
- Wayne WSS30VN listing on Amazon, read October 13, 2026
- Wayne WSB1275 battery listing on Amazon (sold by Amazon.com), read October 13, 2026
- Zoeller: Model 508 12-volt backup technical data sheet (FM3124, 0918), read October 13, 2026
- Zoeller: Aquanot Spin 508 (508-0005) product page, read October 13, 2026
- PumpSpy 2000 W battery backup listing on Amazon (sold by PumpSpy Technology), read October 13, 2026
- PumpSpy PS1275 battery listing on Amazon (sold by PumpSpy Technology), read October 13, 2026
- Liberty Pumps: SJ10-Series SumpJet specifications (SJ10_P3 R05/2025), read October 13, 2026
- Battery University: BU-802, what causes capacity loss, read October 13, 2026
- CPSC recalls database (SaferProducts.gov REST service), all 10,047 recalls, read October 13, 2026
Related: best power station for a sump pump · how much power a sump pump uses · safety rules.
Basement Watchdog Special CONNECT (BWSP)Battery backup sump pump
$279 at Amazon