Battery Backup for Sump Pump Systems


Table of Contents

Sump pump systems are often a last line of defence against basement flooding, and for that reason their reliability is key. A sump pump will need to predictably detect rising water levels in the sump well, and start in response. A primary sump pump systems, attached to AC mains power will generally be all that is needed, but “generally” is not a strong assurance with flooding conditions are often connected with electrical failures. The same downpour that could lead to a basement flood could also reasonably be accompanied by an electrical outage.


Covering your A**

It’s all about redundancy. Sump pumps are at their best as protection against flooding when they will not fail to start or not run out of power. A basic primary sump pump  has an AC-powered pump, a float system, and a piping system to take sump well water away. That’s great if nothing goes wrong, but things going wrong are exactly the situation that needs to be protected against.

For this reason, a secondary sump pump systems may also be AC-powered, but will also have a battery backup. Some other secondary pumps will be powered by battery alone.


Battery power requires a battery, a regulator, and a supply of charging power, usually supplied by AC but at times powered by solar charging. The intent of a battery backup is to have an always-ready source of power for the secondary pump. It should be able to operate unattended, both when charging the battery and when operating.


If the secondary pump is also powered by AC, then it can assist the primary pump if needs get heavy or if the primary pump fails but AC power remains available.

Should power fail, the secondary pump should be able to provide enough pumping to bridge a surge in sump pump needs, preventing flooding until AC power is restored or the need for pumping is alleviated.

A robust system will not just be able to operate when the primary pump is not working, but should ideally also monitor its own state of operation, reporting on the condition of the backup battery and float mechanism.


More sophisticated systems can also provide remote alerts to warn of problems when the homeowner is not in the house, letting them know of the secondary sump pump’s operation and state of readiness.

Hardware Options

Battery recharging

If the sump pump backup battery is solar powered, the solar system should be sized so as to be able to recharge the batteries relatively quickly. Expertise is required to determine the appropriate solar panel array, charging regulator, and battery storage suited to the expected duration of power outage and electrical draw of the secondary sump pump.


The battery used in a sump pump backup system should be capable of supplying power to the pump for a sustained period. The recommended batteries for this use are deep cycle marine “maintenance free” batteries. If the battery is not a maintenance free (sealed) battery, it will need occasional addition of water to maintain fluid levels. Some backup systems do provide a fluid level monitoring system. Whether maintenance free or not, the power needs of a sump pump make a deep cycle battery (as opposed to a car battery) mandatory.

Duration of operation

The duration of operation anticipated for a sump pump battery system depends on the circumstances under which the pump will operate. In many areas power interruptions are of short duration, and a sump pump will not need to operate for long before power is restored. In rural areas however, longer-lasting battery arrays might be appropriate.

Pump capacity

Off the shelf backup pump systems range in capacity from about 1000 gallons per hour (3785 litres per hour) to 5000 gallons per hour (19000 litres per hour), measured at a 10 foot (3 metre) rise.

Unattended operation

Sump pumps, and more especially backup sump pumps, are designed for unattended operation, turning on and off when needed. Beyond basic functioning, unattended operation can also include monitoring the battery, float operation, and power supply. Remote operation using wireless technologies is also becoming more common, with some systems able to be monitored on a cell phone.


Contact Master Drain when installing a sump pump or backup sump pump system. We are able to assess the ideal choice of capacity, power duration, and manufacturer to suit your needs.

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