I pick the Zoeller Aquanot Spin 508: 1,800 gallons an hour at 10 ft on a real battery, and it tests itself. To add a backup for less, get the Wayne ESP25N. To keep your own pump running in an outage, get the PumpSpy BU-2000.
Best for lifts of 10 to 15 feet$488.98 at AmazonPrice as of Oct 24, 2026, 5:30 AM EDT
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.
How much water each backup moves at your lift
Gallons per hour at 5, 10 and 15 ft, from each maker’s own table.
Sources: Zoeller FM3165 data sheet (gal/min × 60, at 12.1 V on a deep-cycle battery); Wayne ESP25-N and WSS30Vn manuals; Basement Watchdog combination system manual. The PumpSpy BU-2000 has no pump of its own; it moves what your AC pump moves.
Most at 15 ft: Zoeller 508
1,200 gallons an hour at 15 ft, twice what the Wayne ESP25N moves there.
Tie at 5 ft: Zoeller and ESP25N
Both list 2,340 gallons an hour at 5 ft of lift.
Lowest here: CITE-33’s backup
1,000 gallons an hour at 10 ft. It earns its place on pit size, not flow.
Read the test method
Zoeller says some makers rate DC pumps 40 to 80% higher than real battery output.
The number on the box is usually the flow at 0 ft. Nobody’s basement has 0 ft of lift. The water has to climb from the pit to where the pipe leaves the house, and every foot costs flow. That’s why this page lines the pumps up at 5, 10 and 15 ft.
Zoeller rates its 508 on a real 12 V deep-cycle battery at 12.1 V. Its data sheet warns that some makers test DC pumps to marine standards that read 40 to 80% higher. Wayne and Basement Watchdog don’t state their test voltage, so treat close numbers as close.
Check valve built in; AC check valve, tee and adapter included
3-year warranty
Cons
Needs an 18 in wide, 22 in deep pit
Battery sold separately
High-water sensor is an extra part
Sold by a third-party seller, Voomi Supply
12 V DC1,800 gal/hr @ 10 ft22 ft shut-off18 in pit min.Group 27–31 case3 years
Buy it if
Your pipe climbs 10 ft or more before it leaves the house, your pit is at least 18 in across, and you want the backup to tell you when something’s wrong before a storm.
The Aquanot Spin 508 is Zoeller’s 12 V battery backup system: a DC pump, a controller and a battery case. This 508-0005 listing was new, in stock and sold by Voomi Supply on Oct 22, 2026, and the photo matches Zoeller’s data sheet.
Flow is the reason it’s my top pick. Zoeller’s table gives 39 gallons a minute at 5 ft, 30 at 10 ft, 20 at 15 ft and 6 at 20 ft. That’s 2,340, 1,800 and 1,200 gallons an hour at the three lifts on the chart.
Those numbers are honest ones. Zoeller says it tests on a fully charged 12 V deep-cycle battery at 12.1 V, and warns that some makers use marine test methods that read 40 to 80% higher. Shut-off is 22 ft, and Zoeller says not to install it over 20 ft of total head.
The controller does the watching for you. Zoeller lists self-testing diagnostics, multi-stage charging, and alerts for a power outage, pump run, pump cycle, battery fault, switch fault and pump fault. There’s a Test button and an Alarm Silence button on the front.
The pump stands on its own legs beside the main pump, with 9 ft leads and a quick-disconnect discharge. A check valve is built into the DC pump, and the box adds a check valve for the AC pump, a tee and an adapter, so it can tie into your existing pipe.
Plan the battery and the pit before you buy. The case fits group 27, 29 and 31 batteries up to 13 by 7½ by 9½ in. Zoeller asks for a deep-cycle size 27 with at least 175 minutes of reserve capacity, and a pit at least 18 in wide and 22 in deep.
How long will it run? Zoeller says about 5½ hours of nonstop pumping on a 175-minute battery. Most backup running is on and off, so one charge covers much longer than that. A second battery case (P/N 10-5184) adds a battery.
I’ve used this system. My call: if your discharge climbs a full basement wall or more, this is the backup that still moves real water at the top of the climb, and it tells you when it needs you.
12 V DC1,680 gal/hr @ 10 ft1-1/2 in NPTGroup 27 case20–25 s run-on2 years
Buy it if
Your main pump is in good shape, your lift is 10 ft or less, and you want a separate backup pump with its own float.
Skip it if
The discharge climbs more than 10 ft. At 15 ft it moves half of what the Zoeller 508 does.
The ESP25N is Wayne’s 12 V backup pump with a control box and battery case. Wayne’s manual is plain about the job: it’s a battery backup that “does not replace a regular pump”. It was new, in stock and sold by Amazon.com on Oct 22, 2026.
Wayne’s table gives 2,900 gallons an hour at 0 ft, 2,340 at 5 ft, 1,680 at 10 ft and 600 at 15 ft. The Amazon title says 2,700 at 0 ft. I go by Wayne’s manual. Up to about 10 ft of lift, it keeps pace with the Zoeller.
The motor is a dielectric-oil-filled 12 V DC motor in a coated steel housing, with a stainless shaft and a thermoplastic impeller and volute. The discharge is 1-1/2 in NPT, and Wayne says to pipe it in 1-1/4 or 1-1/2 in rigid PVC.
You can pipe it two ways, per the manual. Method 1 gives it its own discharge line out of the house. Method 2 ties it into your existing pipe with a Y, and then a check valve goes on each pump. Wayne says a check valve must be used on both pumps either way.
The float goes at least 10 to 12 in above the pit floor, above the main pump’s on level. That way the backup only runs when the main pump falls behind or loses power. After the float drops, the pump runs another 20 to 25 seconds, so it doesn’t short cycle.
Wayne says the system runs best with AGM batteries, and the oversize case takes a 12 V AGM up to a group 27 frame. One battery only; Wayne says not to wire batteries in parallel. Wayne’s listing recommends its WSB1275, a 12 V 75 Ah sealed battery sold by Amazon.com: Check it on Amazon.
The control box charges the battery and stops it from overcharging. Its lights read green for full, yellow for partly charged and red for flat or bad. Wayne’s manual explains how to get a true reading: unplug the main pump and the charger, lift the float, then read the lights.
I’ve used this pump. My call: for a normal basement with a short lift and a sound main pump, it’s the simplest way to add a real second pump, and Wayne’s two piping methods fit most pits.
Combos that replace your main pump too
Best for replacing a tired primary pump
Wayne WSS30VN combo
Wayne WSS30VN, ½ HP primary + 12 V backup, preassembled
½ HP + 12 VDC 1,500 gal/hr @ 10 ft15 in basin min.Vertical floats1-1/2 in NPT3 years
Buy it if
Your main pump is old or noisy, you’d rather replace it now than add a backup beside it, and the basin is at least 15 in across.
Skip it if
Your main pump is fairly new. Add the Wayne ESP25N beside it and keep the good pump.
The WSS30VN is Wayne’s preassembled combo: a ½ HP primary pump and a 12 V backup pump on one piped stand. It was new, in stock and sold by Amazon.com on Oct 22, 2026.
It makes sense when the main pump is due anyway. Wayne’s manual gives the primary 5,100 gallons an hour at 0 ft, 4,500 at 5 ft, 3,840 at 10 ft and 3,060 at 15 ft. You replace the old pump and add the backup in one job.
The backup half is close to the ESP25N. Wayne lists the DC pump at 2,700 gallons an hour at 0 ft, 2,130 at 5 ft, 1,500 at 10 ft and 720 at 15 ft. It’s a 100 W permanent magnet brushed motor; the primary is a single-phase, oil-filled motor.
Both pumps stand 11½ in tall on a 9¾ in base. Wayne’s sheet lists a cast iron volute and glass-reinforced thermoplastic impellers. The discharge is 1-1/2 in NPT. The primary turns on at about 9 in and off at about 4 in; the backup comes on at 10 to 12 in.
Check the basin first. Wayne’s manual asks for a basin at least 15 in across and 22 in tall. The Amazon bullet says 16 in. I go by Wayne. Leave at least 1 in between the system and the basin wall, per the manual.
Both pumps use vertical float switches. Wayne says to replace the switch every two years and to inspect the system three to four times a year for debris on the switch or float. That’s a real cost of ownership, so put it on the calendar.
Wayne recommends its WSB1275 75 Ah maintenance-free battery, sold separately; the battery case is in the box, and LED lights show charge status. The warranty is three years, a year longer than the ESP25N.
I’ve used this combo. My call: when the main pump is near the end of its life, this is the cleanest way to get a new primary and a backup in a 15 in basin without building the piping yourself.
Controller with lights and alarms for power, battery and pump
Preassembled and preplumbed
Sold by Glentronics, the maker
Cons
Backup only 1,000 gal/hr at 10 ft
Listing and manual disagree on backup flow
Check battery fluid every 4 to 6 months on a wet cell
2-year warranty
⅓ HP + 12 VDC 1,000 gal/hr @ 10 ft10 in pit min.17¾ in tall0.4 A charger2 years
Buy it if
Your pit is a small 10 to 14 in liner where nothing else fits two pumps, and the lift is short.
Skip it if
Your basement takes on a lot of water in a storm. The backup moves the least here; the Zoeller 508 moves almost twice as much at 10 ft.
The CITE-33 is a Basement Watchdog combo from Glentronics: a ⅓ HP primary pump, a 12 V backup pump and a monitoring controller on one preplumbed stand. It was new and sold by Glentronics, the maker, with 19 in stock on Oct 22, 2026.
Its reason to exist is size. Basement Watchdog’s manual says the combo fits a pit as small as 10 in wide and 14 in high, “the size of a 5 gallon bucket”. It measures 17¾ in from the bottom of the pump to the top of the Y that meets your pipe.
The primary is the strong half. The manual lists 3,100 gallons an hour at 10 ft, and the listing adds 3,720 at 0 ft, with a copper-wound PSC motor. That’s in line with other ⅓ HP pumps on the chart.
The backup is the weak half. Basement Watchdog’s manual lists it at 1,000 gallons an hour at 10 ft. The Amazon bullet says 1,500 at 10 ft. I go by the manual, which puts it last on the flow chart.
The controller is the best part. The manual lists warning lights and an alarm for power loss, low battery fluid, a backup pump problem and a battery fault, with a red button to silence it. It uses a 0.4 A charger, and the listing names the BW-27AGM battery as compatible.
Watch the battery type. The fluid sensor reads a Basement Watchdog wet-cell battery; with a sealed AGM, the manual says to clip the sensor to the positive post. On a wet cell, check fluid every 4 to 6 months. The AGM skips that: Check it on Amazon.
Basement Watchdog’s manual says its standby battery runs the backup for about 50 hours at a 10% duty cycle, meaning six minutes of pumping each hour. It also says the battery will not run the primary pump. The warranty is two years in sump use.
I’ve used this combo. My call: in a pit too small for anything else on this page, it’s the way to get two pumps and a real alarm, as long as your basement doesn’t flood fast.
Backup power for the pump you already have
The BU-2000 has no pump of its own, so it isn’t scored against the four backup pumps above.
PumpSpy BU-2000 backup power system. Product photo: Amazon.
The BU-2000 isn’t a pump. It’s PumpSpy’s backup power unit: an inverter and charger that runs your existing AC sump pump from a 12 V battery when the power goes out. The PumpSpy BU-2000 on Amazon was new, in stock and sold by PumpSpy on Oct 22, 2026.
That’s the other way to answer “battery backup”. A DC backup pump is a second, smaller pump. This keeps your main pump running, so you get its full flow. A ½ HP primary that moves 3,840 gallons an hour at 10 ft keeps moving that, for as long as the battery lasts.
PumpSpy’s manual lists 2,000 W rated output, 4,000 W surge and a pure sine wave at 120 VAC, with soft start. When the power’s on, house power passes straight through to the two outlets, and the unit charges the battery.
Where it does well
Runs your full-size AC pump at full flow
Pure sine wave, 2,000 W, 4,000 W surge
Two outlets: can run two pumps up to 16.6 A total
Charges the battery while the power’s on
3-year warranty; sold by PumpSpy
What to watch
No second pump: no help if the main pump fails
Run time depends on your pump’s draw
Battery sold separately
Fans need cleaning every 3 months
When the power fails, it switches to the battery. Both outlets together can carry up to 16.6 A continuous, so it can run two pumps whose draw adds up to less than that. Over 16.6 A, it shuts down, sounds an alarm and shows a red fault light.
Run time is the trade-off. The battery now feeds a full AC pump through the inverter, so your pump’s draw sets how long it lasts. Check your pump’s nameplate amps and the battery’s amp hours before a storm, not during one.
The low-voltage alarm sounds when the battery falls below 10 V. PumpSpy recommends its own maintenance-free AGM deep-cycle battery, sold separately by PumpSpy: Check it on Amazon. The manual says deep-cycle batteries generally last 3 to 5 years in this job.
Upkeep is light. PumpSpy says to vacuum the cooling fans at least every three months and to test the battery every six months. Mount it where it stays between 14 and 120 °F, in a well-ventilated spot, and don’t use an extension cord.
I’ve used this unit. My call: if your pump is healthy and power cuts are the threat, this gives you your own pump’s full flow in an outage. If the pump itself might fail, pair it with a DC backup pump.
The four backup pumps side by side
Flow is the 12 V backup pump’s, from each maker’s table.
Pit sizes are diameter × depth from each manual; the ESP25N stands beside your main pump and needs room for its float 10 to 12 in up. Every pick needs a 12 V deep-cycle battery bought separately.
Second pump or backup power: which kind you need
“Battery backup” means two different things, and they protect against different failures.
What goes wrong
Second 12 V pump (Zoeller, Wayne, Watchdog)
Backup power (PumpSpy)
Power goes out
Covers it
Covers it, at full AC flow
Main pump motor fails
Covers it
No help
Main pump’s float sticks
Covers it: separate float
No help
Storm brings more water than the main pump can move
Both pumps run
Only the main pump
Long outage
Longer run time per charge
Shorter run time per charge
Flow during an outage
Smaller DC pump’s flow
Your full AC pump’s flow
A backup guards against two failures: the power goes out in a storm, or the main pump quits. A second pump covers both, because it has its own float and its own power. Backup power covers only the first.
If you can afford both, they work together. Plug the main pump into backup power, and put a DC pump beside it. For the water-powered kind that runs on city water pressure, see battery vs water-powered backups.
How to measure the lift your backup works against
One tape measurement tells you which row of the flow chart to read.
Lift is measured straight up from the water level, not along the pipe. Sources: Wayne ESP25-N manual (float height); Zoeller FM3165 (20 ft total head limit).
1
Find the backup’s on level
Wayne sets its backup float at least 10 to 12 in above the pit floor and above the main pump’s on level. That’s the water level where the backup starts work.
2
Measure straight up
From that level up to the highest point of the discharge pipe, usually where it turns to go out through the rim joist or wall.
3
Round up
If it’s 8 ft, read the 10 ft row. A long run, extra elbows and two check valves all cost flow on top of the climb.
4
Check the limit
Zoeller says not to install its 508 above 20 ft of total head. If you’re near 15 ft, compare each maker’s 15 ft number before you buy.
The climb is usually the pit depth below the slab plus the height of the pipe up the foundation wall to where it exits. A walkout basement or a crawl space pit may need far less. Measure yours; it’s the one number that decides between these pumps.
Pipe size matters too. Wayne says to use 1-1/4 or 1-1/2 in rigid PVC, and that smaller pipe cuts flow. Our check valve size guide covers the two sizes.
How long a battery backup runs a sump pump
The makers give run time two ways: nonstop, and on and off.
Maker’s statement
Battery
What it means
Zoeller 508: about 5½ hours of nonstop pumping
Deep-cycle, 175 min reserve
A worst case: the pump never stops
Basement Watchdog: about 50 hours at a 10% duty cycle
Its standby battery
Six minutes of pumping each hour
Basement Watchdog: about 100 hours at 10%
Its Big standby battery
A larger battery doubles it
PumpSpy: alarm when the battery falls below 10 V
12 V deep-cycle
Depends on your AC pump’s draw
Duty cycle is the share of each hour the pump runs. A pump that runs one minute in ten is at a 10% duty cycle. In a hard storm with a high water table, that share climbs, and run time falls with it. That’s why Zoeller quotes the nonstop number.
More battery is the simple fix. Zoeller sells a second battery case (P/N 10-5184) for a second battery. Wayne, by contrast, says its ESP25N takes one battery only.
For backup power like the PumpSpy, work it out from your own pump. The nameplate shows its amps. Multiply by 120 to get watts while it runs. A bigger pump drains the battery faster, so a ½ HP pump gets less time per charge than a ⅓ HP pump on the same battery.
Which battery to buy for a sump pump backup
No pick here includes the battery. Each maker names the kind it wants.
Pick
Maker asks for
Matching battery
Zoeller 508
Deep-cycle, size 27 or larger, 175 min reserve or more
Zoeller Aquanot AGM 10-1450 (180 min)
Wayne ESP25N
12 V AGM, up to group 27, one battery only
Wayne WSB1275, 75 Ah sealed
Wayne WSS30VN
75 Ah maintenance-free
Wayne WSB1275
Basement Watchdog CITE-33
Basement Watchdog battery; no car batteries
BW-27AGM maintenance-free
PumpSpy BU-2000
12 V deep-cycle
PumpSpy 75 Ah AGM
Use a deep-cycle battery, never a car battery. Basement Watchdog’s manual rules out car batteries; they’re made to start engines, not to run a pump for hours. Wayne says its system works best with AGM batteries, which cost a bit more and can last longer.
AGM or sealed batteries skip the water top-ups. With a wet-cell battery, Basement Watchdog says to check the fluid every 4 to 6 months, and to top up with distilled water. Wear eye protection; battery acid is corrosive, per Wayne.
Reserve capacity, in minutes, is the number to compare between deep-cycle batteries. It’s how long a full battery can carry a set load. Zoeller’s own Aquanot batteries run 140 to 180 minutes; it asks for 175 minutes at least.
Plan to replace it. PumpSpy’s manual says deep-cycle batteries generally last 3 to 5 years in sump backup work, and says to test the battery every six months.
Will it fit your sump pit
Two pumps and two floats need room. Check the makers’ minimum pit sizes.
Pick
Minimum pit
Height to the pipe
Basement Watchdog CITE-33
10 in wide, 14 in high
17¾ in to the top of the Y
Wayne WSS30VN
15 in across, 22 in tall
Pumps 11½ in tall
Zoeller 508
18 in across, 22 in deep
Free-standing on legs
Wayne ESP25N
Room beside the main pump
Float 10–12 in above the floor
PumpSpy BU-2000
Nothing in the pit
Mounts near an outlet
Measure the inside of the pit liner at the top, and the depth from the rim to the floor. If it’s too small for a second pump, a combo built for small pits, or backup power with no pump at all, is the answer.
Floats need room to swing. A float that rubs the liner or the other pump’s pipe can stick. Our float switch types guide shows how much room each kind needs.
What the alarms and tests tell you
A backup you never check is a backup you can’t trust.
Lights and alarm for power, fluid, backup pump, battery
Lift each float with a pencil
Wayne ESP25N
Charge lights: green, yellow, red, red blinking
Unplug main pump and charger, lift the float
Wayne WSS30VN
Charge status lights
Fill the basin with water
PumpSpy BU-2000
Fault light and alarm; alarm below 10 V
Unplug it from the wall, run the pump
Wayne’s manual has a useful catch. With the power on, its charge lights show the charging state, not the true battery voltage, so a bad battery can still read fine. To check it, unplug the main pump and the charger, lift the float, and read the lights after the pump stops.
For an alarm that also watches the main pump, see our sump pump alarm picks. A high-water alarm catches a stuck float on either pump.
What installing a battery backup involves
The makers’ manuals agree on the parts that matter.
1
Check valve on each pump
Wayne says a check valve must be used on both the primary and the backup discharge. Without one, water from one pump runs back down through the other.
2
Pick the piping method
A separate line out of the house, or a tie-in to the existing pipe with a Y. Wayne’s manual covers both.
3
Set the float above the main pump’s
The backup’s float sits above the main pump’s on level, so the backup runs only when the main pump can’t keep up.
4
Plug into a GFCI outlet
Wayne’s manual says a ground fault circuit interrupter is required. All wiring is a job for a qualified electrician, per Wayne and Zoeller.
5
Charge the battery, then test
Let the charger fill the battery, then fill the pit with water and watch both pumps run.
Plan for the pit to be out of action for a while. Wayne warns that installation may take several hours, so have a way to remove water while the pumps are off. Do it on a dry day.
Keep the battery off the floor and in its case, and keep sparks away from it. Wayne’s manual warns that charging batteries can release hydrogen gas. For costs, see cost to install a sump pump.
Keeping a battery backup ready
The makers’ own schedules, in one place.
How often
Task
Source
Every 3 months
Vacuum the inverter’s cooling fans
PumpSpy BU-2000 manual
3–4 times a year
Inspect for debris on the switch and float
Wayne WSS30VN manual
Every 4–6 months
Check wet-cell battery fluid
Basement Watchdog manual
Every 6 months
Test the battery
PumpSpy manual
1–2 times a year
Lift both floats, clean the pit and strainers
Basement Watchdog manual
Every 2 years
Replace the float switch
Wayne WSS30VN manual
Every 3–5 years
Replace the battery
PumpSpy manual
The best test copies a real outage. PumpSpy’s install steps have you unplug the unit from the wall and then run the pump. With a DC backup, unplug the main pump while there’s water in the pit and watch the backup take over.
If your main pump has stopped altogether, start with our sump pump not working guide before you replace anything.
Recall check on backup chargers and pumps
2000 recall: some backup chargers
CPSC recall 00-100 covered about 29,000 battery chargers in Flotec and Sears backup sump pump systems from Sta-Rite. They could overheat and catch fire. If you have an old one, check it at cpsc.gov.
Our picks aren’t on any list
No pump, charger or battery on this page was on CPSC’s recall list when I checked on Oct 21 and 22, 2026.
How to pick the right battery backup
Your situation
Option
Why
Discharge climbs 10 ft or more
Zoeller Aquanot Spin 508
Most flow at 10 and 15 ft
Short lift, good main pump
Wayne ESP25N
A second pump with its own float
Main pump is old, 15 in basin
Wayne WSS30VN
New primary and backup in one
Pit only 10 to 14 in wide
Basement Watchdog CITE-33
Fits a 10 in pit
Outages are the risk, pump is healthy
PumpSpy BU-2000
Your own pump at full flow
You want the most protection
PumpSpy + a DC pump
Covers outages and pump failure
Work in this order: what fails, then lift, then pit. Decide whether you’re guarding against outages, pump failure or both. Then measure your lift and read the flow chart. Last, make sure the pick fits your pit.
If your basement has ever taken on water during a storm, yes. Storms bring both heavy rain and power cuts, and a main pump can’t run without power. A backup with its own float also covers a failed main pump.
Can I put a battery backup on my existing sump pump?
Yes, two ways. Add a 12 V backup pump beside it, like the Wayne ESP25N or Zoeller 508, or plug your pump into backup power like the PumpSpy BU-2000. The first also covers a failed pump.
How long will a battery backup run a sump pump?
Zoeller says about 5½ hours nonstop on a 175-minute battery. Basement Watchdog says about 50 hours at a 10% duty cycle on its standby battery. Real run time depends on how often the pump cycles.
How can I keep my sump pump running during a power outage?
Use backup power that runs your AC pump from a battery, like the PumpSpy BU-2000, or add a 12 V DC backup pump. A generator works too, if someone’s home to run it.
What kind of battery does a sump pump backup need?
A 12 V deep-cycle battery, never a car battery. Wayne says AGM works best in its ESP25N. Zoeller asks for a size 27 or larger with at least 175 minutes of reserve capacity.
How long does a sump pump backup battery last?
PumpSpy’s manual says deep-cycle batteries generally last 3 to 5 years in sump backup work. Test it every six months, per PumpSpy.
Does a battery backup sump pump need its own discharge line?
No. Wayne’s manual shows two ways: a separate line, or a tie-in to your existing pipe with a Y. Either way, each pump needs its own check valve.
How high should the backup float be?
Above the main pump’s on level. Wayne puts its backup float at least 10 to 12 in above the pit floor, so the backup runs only when the main pump falls behind.
Can a battery backup run two sump pumps?
Backup power can. The PumpSpy BU-2000 has two outlets and carries up to 16.6 A combined. A DC backup pump is a single pump.
Is a combo system better than a separate backup pump?
Only if the main pump needs replacing. A combo like the Wayne WSS30VN replaces it and adds a backup in one unit. If your main pump is sound, add a separate backup.
What does duty cycle mean for a sump pump backup?
It’s the share of each hour the pump runs. At a 10% duty cycle, the pump runs six minutes an hour. Higher duty cycles drain the battery faster.
Do I need a GFCI outlet for a battery backup sump pump?
Wayne’s manual says yes, a GFCI is required for its ESP25N. Plug the charger into a GFCI-protected outlet, and have an electrician handle any wiring.
How I picked them
Why trust me
Written by Isaac Daniels, a licensed journeyman plumber in Georgia (license #JP507711), who has used every backup on this page. Flow, pit sizes and warranties come from Zoeller’s, Wayne’s, Basement Watchdog’s and PumpSpy’s own manuals; seller and stock from Amazon’s Creators API.
How I picked
Flow at real lift first: 5, 10 and 15 ft from the maker’s table.
One pick per common basement problem, plus backup power for a healthy pump.
A spec score for the four backup pumps, from four checks shown below. Your lift still decides first.
Links only to listings that were new and in stock at our check.
The spec score, check by check
Each check scores 0 to 10 and counts one quarter. It’s our score from Zoeller’s, Wayne’s and Basement Watchdog’s published figures, not a customer rating or a field test. Only the 12 V backup pump is scored; the combos’ AC primaries and PumpSpy’s BU-2000, which has no pump, aren’t.
Measure your lift and your pit first: a high score doesn’t help if the unit won’t fit or your discharge climbs past its table.
Check (weight)
How it’s scored
Flow at 10 ft (¼)
Backup pump flow at 10 ft of lift, from the maker’s table: 10 for 1,700 gal/hr or more; 9 for 1,400 to 1,699; 7 for 1,000 to 1,399; 5 below 1,000
Flow at 15 ft (¼)
Backup pump flow at 15 ft of lift: 10 for 1,000 gal/hr or more; 8 for 600 to 999; 6 below 600 or not published
Alerts (¼)
10 for self-tests plus fault alerts; 9 for an audible alarm with lights for power, battery and pump; 8 for charge-status lights only
Warranty (¼)
Maker’s warranty: 10 for 3 years; 8 for 2 years
Total
Average of the checks, to one decimal
Pick
Flow at 10 ft
Flow at 15 ft
Alerts
Warranty
Score
Zoeller Aquanot Spin 508
10
10
10
10
10
Wayne ESP25N
9
8
8
8
8.3
Wayne WSS30VN
9
8
8
10
8.8
Basement Watchdog CITE-33
7
6
9
8
7.5
Sources
Zoeller: Aquanot Spin 508 technical data sheet FM3165 (06/22).
Wayne Water Systems: ESP25-N Operating Instructions and Parts Manual 600001-001 B (08/18); WSS30Vn Operating Instructions and Parts Manual 670001-001 D (08/18).
Glentronics (Basement Watchdog): combination sump pump system instruction manual and safety warnings.
PumpSpy: BU-1500/BU-2000 Instruction and Operating Manual 95353-03.
U.S. CPSC: recall listing searched Oct 21, 2026; recall 00-100, Sta-Rite battery chargers for Flotec and Sears backup sump pump systems (Apr 23, 2000).
Amazon listings for all five products and three batteries (seller, condition, stock, model): Creators API, Oct 21, 2026, 6:08 PM.
Amazon Creators API offers, Oct 22, 2026, 6:49 AM EDT: B018A2U1NA (Voomi Supply), B07GJXRZ1V and B07H4S6X9N (Amazon.com), B093MLBW9G (Glentronics, 19 left), B0CSKMTMMD (PumpSpy Technology); all new and in stock. CPSC recall title searches for Zoeller, Wayne, Basement Watchdog, Glentronics, PumpSpy and sump pump, Oct 22, 2026: none for these models.
