- A sump pump backup system is a second pump that takes over when the power fails or the main pump quits, so a storm outage doesn't flood the basement.
- A battery backup runs on a deep-cycle battery for hours rather than days, and the battery needs replacing every few years. It typically costs $800 to $1,800 installed.
- A water-powered backup runs on city water pressure with no battery, but needs a backflow preventer and uses a lot of water. It typically costs $800 to $1,500 installed.
- Halton's flood subsidy specifically excludes water-powered backups, so if you live in Burlington, Oakville or Milton and plan to claim it, choose a battery backup.
Why a backup sump pump matters
A sump pump does its hardest work in the worst weather: heavy rain, a fast spring thaw, a summer thunderstorm. Those are the same conditions that knock out the power. When the pump stops, the pit fills, and the water has nowhere to go but onto your floor.
Power isn't the only risk. Primary pumps fail too. Floats stick, switches wear out, and motors give up with age, often without warning. A backup sump pump sits in the same pit and takes over automatically when the main pump can't keep up.
Whether you need one comes down to what's at stake. If your basement is finished, stores things you can't replace, or has flooded before, a backup is cheap insurance. If the sump rarely runs and the basement is unfinished concrete, a good alarm and a reliable main pump may be enough. We'll give you an honest read either way.
How a battery backup sump pump works
A battery backup sump pump system adds a second pump to your pit, set slightly higher than the main one and powered by a deep-cycle battery. A charger keeps the battery topped up while the power is on. If the power fails, or the water rises past the main pump because it's failed or can't keep up, the backup switches on by itself. Most systems include an alarm so you know it's running.
- Works anywhere: it doesn't depend on city water, so it suits homes on a private well too.
- Limited runtime: a fully charged battery typically lasts from several hours to about a day, depending on the battery and how hard the pump has to work.
- Smaller capacity: a backup usually moves less water than the main pump. It's there to bridge the gap, not to replace the primary.
- Battery upkeep: the battery wears out and typically needs replacing every three to five years.
How a water-powered backup sump pump works
A water-powered backup sump pump uses your home's water pressure instead of electricity. City water runs through a nozzle that creates suction, and that suction lifts water out of the pit. With no battery to run down, it keeps working as long as the water pressure holds.
- Needs good water pressure: the manufacturer's manual we checked calls for at least 40 PSI, so it relies on municipal water. Homes on a private well usually lose water pressure when the power goes out, so it isn't a fit there.
- Needs a backflow preventer: the unit connects your drinking water to a pit full of groundwater, so it has to be installed with an approved backflow device. Ontario's plumbing rules require potable water connections to be protected from contamination, with backflow preventers selected and installed under the CSA B64.10 standard.
- Uses city water to run: depending on the model and your water pressure, it can use from about half a litre to two litres of city water for every litre it pumps out.
- Watch the float: if the float sticks, the unit can keep running and run up a large water bill.
Battery vs water-powered: side by side
| Battery backup | Water-powered backup | |
|---|---|---|
| Power source | Deep-cycle battery | City water pressure |
| Runtime | Several hours to about a day on one charge | As long as water pressure holds |
| Main upkeep | Battery replacement every three to five years | Backflow preventer and float checks |
| Water use | None | About half a litre to two litres per litre pumped |
| Works on a private well | Yes | Not usually |
| Halton flood subsidy | Not excluded | Not eligible |
| Typical installed cost | $800 to $1,800 | $800 to $1,500 |
Typical Hamilton-area ranges before tax.
Why Halton won't subsidize water-powered backups
Halton Region's Basement Flooding Prevention Subsidy covers 100% of disconnecting your weeping tile and installing a sump pump, up to $6,500, for homes in Burlington, Oakville and Milton. Its rules state that water-powered backup sump pumps aren't eligible, because they pose risks to the municipal drinking water supply if they aren't properly installed and maintained.
If you're claiming the subsidy, choose a battery backup, and confirm with the Region what your claim covers before the work starts. Our guide to basement flooding subsidies covers Halton's other rules and the programs in Hamilton, Brantford, Caledonia and Grimsby.
Which backup is right for your home?
For most of the homes we work on, we recommend a battery backup. It's simpler, it doesn't touch your drinking water, and it doesn't put a Halton subsidy at risk.
- Choose a battery backup if you're claiming Halton's subsidy, you're on a private well, or you want the simplest system to live with.
- Consider a water-powered backup if you're on municipal water with strong pressure, long power outages are your main worry, and you're comfortable with the backflow preventer and the water use.
- Either way, make sure the primary pump is in good shape. A backup is the second line of defence, not a fix for a tired main pump.
What a proper backup install includes
A backup pump is only useful if it starts when it should and its water actually leaves the house. Most of the backups we're called to look at weren't broken. They were installed in a way that meant they couldn't do their job.
- Room in the pit for both pumps, with the backup's float set above the main pump's so it only runs when it's needed.
- Its own check valve, and on many installs its own discharge line, so a clogged or frozen line can't take out both pumps at once.
- An alarm that sounds when the backup starts or the battery runs low, so you know the main pump needs attention.
- A charger and battery mounted up off the floor, where the water they're protecting against can't reach them.
- For a water-powered unit, an approved backflow preventer on the water connection, installed to the manufacturer's instructions and the plumbing rules.
If your pit is too small for a second pump, the pit itself may need replacing. We'll tell you before we quote, not after.
What a sump pump backup costs
| Job | Typical cost |
|---|---|
| Battery backup added to an existing sump | $800 to $1,800 |
| Water-powered backup with the backflow preventer a plumber fits | $800 to $1,500 |
| Replacing the main pump at the same time | $500 to $1,400 |
| New sump pit and pump, if there isn't one yet | $1,500 to $3,500 |
Typical Hamilton-area ranges before tax. A second discharge line or a pit too small for two pumps adds to the cost.
No sump yet? Start with our guide to installing a sump pump in an existing basement.
Keeping a backup ready
- Test both pumps a couple of times a year, ideally before the spring thaw and before summer storm season.
- Check the battery charger and alarm, and replace the battery on schedule rather than waiting for it to fail.
- For a water-powered unit, check the float, and ask your municipality whether the backflow preventer needs regular testing.
- Keep the pit clear so neither pump's float can jam.
Backup sump pump questions
How long will a battery backup sump pump run?
Can I add a backup to my existing sump pump?
Why does a water-powered backup need a backflow preventer?
Do I need a backup if I rarely lose power?
Will Halton pay for a backup pump?
Sump work we do
Related guides
Basement Worx works across Hamilton, Burlington, Oakville, Milton, Ancaster, Dundas, Stoney Creek, Waterdown, Cambridge, Brantford, Caledonia and Grimsby.