Wayne ESP25 review: an add-on 12 V backup beside your existing sump pump

This is a research-based review, based on manufacturer specs and published data. We do not test products. Figures come from Wayne Water Systems' ESP25 product page, checked November 1, 2026, plus the safety sources cited below.

The ESP25 is a 12 V DC sump pump that goes into an existing pit next to the primary pump. Its reed float sits a little higher than the primary's switch, so it starts only when the primary has stopped or fallen behind. Wayne pairs it with a smart charger, a thermoplastic battery box and an LED that shows the battery's charge.

Wayne's runtime claim is unusually concrete. Instead of a duty-cycle percentage, it says the ESP25 offers up to 26 continuous hours of protection at 5 gallons per minute of incoming water on its 75 Ah battery. That makes it easier to judge against your own pit than most backup ratings.

Who should buy it

• Owners with a sound primary pump who want outage and breaker-trip protection without replacing it.
• Pits with moderate inflow. 1,680 GPH at 10 ft is 28 gallons a minute, several times Wayne's 5 GPM runtime scenario.
• Homes with a 1-1/4 inch discharge as well as 1-1/2 inch: Wayne lists both for its in-line install.

Who should skip it

• Anyone who wants fault alerts. Wayne lists only an alarm when the pump runs and an LED for battery charge. The Zoeller Aquanot Spin 508 and Big Dog CONNECT report pump and battery faults.
• Homes that need phone alerts. Wayne does not list Wi-Fi for the ESP25.
• Owners also replacing the primary pump. Wayne's WSS30V combo pairs this same backup with a 1/2 HP primary, pre-plumbed.

Strengths

• Clear runtime claim. Up to 26 continuous hours at 5 GPM of inflow on a 75 Ah battery, stated with its assumptions.
• Solid flow curve. 1,680 GPH at 10 ft, with Wayne publishing figures at 0, 5, 10 and 15 ft.
• Flexible plumbing. Fits 1-1/2 or 1-1/4 inch discharge pipe.
• Adjustable reed float, which Wayne describes as user-adjustable for automatic operation.
• Corrosion-resistant thermoplastic battery box and reinforced thermoplastic pump construction.

Drawbacks

• Limited alerts. The alarm sounds when the 12 V pump runs. Wayne does not list alerts for a failed pump, a stuck switch or a bad battery.
• No automatic pump exercise listed by Wayne, so manual checks are on you.
• Battery sold separately. Wayne's recommended WSB1275 is a 75 Ah unit.
• Model confusion. Retailers also list an ESP25N with different ratings from the ESP25 figures on Wayne's page. Match the exact model on any listing.

How it compares

The ESP25 against the other add-on backups we review. Each maker quotes runtime under its own assumptions, so treat that row with care.

Using it in a long outage

Reading the 26-hour claim

Wayne's scenario is 5 gallons a minute of incoming water. Over 26 hours that is about 7,800 gallons the ESP25 handles on one 75 Ah battery (our arithmetic from Wayne's figures). If a storm sends 10 gallons a minute into the pit, expect roughly half the hours. If it sends more than about 28 gallons a minute, the pump's 10-foot rating, the pit will rise even with the pump running nonstop.

To find your inflow, time how fast the pit refills after the primary pump shuts off in a hard rain. Measure the pit's diameter and the rise in inches, and work out gallons per minute; an 18-inch pit holds about 1.1 gallons per inch of depth.

When the outage runs past a day

A long outage outlasts any single battery. Two options keep the pit under control: run the smart charger from a portable power station or an outdoor generator to refill the battery, or run the primary pump directly from a generator with enough starting watts. Our best generator for a power outage guide includes sump pump sizing, and the power station for a refrigerator guide shows how station capacity is calculated.

Install and upkeep

1. 01Set the ESP25 so its float trips above the primary's on point, and give the floats room so they do not snag each other.
2. 02Tie the discharge into the existing line with a check valve, per Wayne's manual. Hire a plumber if cutting PVC is unfamiliar.
3. 03Plug the charger into a GFCI-protected outlet. The 2020 National Electrical Code requires GFCI protection on basement receptacles (Electrical Safety Foundation).
4. 04Charge the battery in a ventilated spot. Lead-acid batteries release hydrogen while charging; keep sparks and flames away.
5. 05A few times a year, unplug the primary and fill the pit until the ESP25 starts and the alarm sounds. Watch the LED for charge status.