Drains & Sewers

Sump Pumps

The pump in the pit is the last thing standing between groundwater and a finished basement, and it is almost always the switch that goes first.

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How the system actually works

A sump system has three parts and all three have to do their job. Weeping tile, the perforated pipe running around the footing or under the slab, collects groundwater before it can push through the floor joint. That tile drains by gravity into the sump pit. The pump lifts whatever collects in the pit up and out of the building through the discharge line.

The pit is not just a hole. It needs enough depth that the pump shuts off with water still covering the volute, and enough width that the float can swing without catching the discharge pipe or the wall. Undersized pits make pumps short-cycle, and short-cycling is what wears them out. Starting is the hardest thing a motor does, and a pump that starts forty times an hour ages accordingly.

Sumps are common in Toronto basements for straightforward reasons: clay soil that holds water, a table that comes up hard during spring melt, and housing built before below-grade waterproofing meant much. What a sump does not do is make a basement dry by itself. It manages groundwater arriving through the weeping tile. Water coming through a wall crack, over the top of the foundation, or backwards out of a floor drain is a different problem, and a bigger pump will not touch it.

Pumps, switches, and the parts that fail

Pedestal pumps carry the motor on a shaft above the pit, so the motor stays dry and is easy to get at. They are louder and they need vertical clearance. Submersibles sit in the water, run quieter, generally move more, and are what most installations get today. Neither one is wrong. Pit depth, pit diameter and the opening above it usually make the decision.

Switches are what actually fail, not motors. A tethered float hangs on a cord and needs room to swing; in a narrow pit it catches on the pipe or the wall and either never starts or never stops. A vertical float rides a rod, takes less room, and fouls with silt and iron bacteria until it sticks. Electronic and diaphragm switches have no moving float and fail their own way, usually by nuisance-cycling once a film builds on the sensor. When a pump comes out early, the motor is usually fine and the switch is the reason.

A check valve on the discharge stops the standing column of water in the pipe from falling back into the pit each time the pump shuts off. Without one, the pump refills its own basin and starts again, which is short-cycling by another route. Check valves also chatter and eventually weep, and fitted on a union they are worth replacing whenever the pump is.

Where the water goes matters as much as the pump

Discharge has to reach grade, well clear of the foundation, and be sloped so the line drains itself. Two metres from the wall is a sensible minimum and further is better. It also has to release somewhere the water will actually leave: dumping onto a flat bed beside the house sends it back down into the weeping tile it came from, and the pump spends the season moving the same water in a circle.

It must not tie into the sanitary sewer. Groundwater in the sanitary system is what overloads the mains during a heavy summer storm and pushes sewage back into basements, which is the thinking behind Toronto's downspout disconnection and drainage requirements. Older houses sometimes have a sump or weeping tile connection into the sanitary from decades back. If we find one, we will show you and explain what correcting it involves.

Winter is the other routing problem, and it catches people. A discharge that runs uphill, ends in a low spot, or sits along a shaded north wall will freeze. The pump then runs against a closed pipe with the check valve holding pressure behind it, and either the motor cooks or a fitting splits. We slope the line so it drains back, keep the exterior run short, and where the layout forces the issue, fit a removable winter extension or a freeze-relief opening so the pump has somewhere to push.

Backup power, and testing before you need it

Storms take the power out. That is the exact moment a sump matters most, which is the whole argument for a backup. A DC battery backup is a second pump on its own float with a charger and a deep-cycle battery behind it. It buys hours, not days, and how many hours depends on how fast the pit refills. A water-powered backup uses municipal supply pressure instead of a battery, needs no charging, but consumes potable water while it runs and requires backflow protection at the connection.

Neither one removes the need to look at it. A battery is a consumable and will not outlive the pump it protects, and a backup system with a dead battery is a decoration. Test the whole thing in late winter, before the melt rather than during it.

Pour two buckets of water into the pit and watch the full cycle
Confirm the float lifts freely and the pump shuts off cleanly, without hunting
Listen for the check valve seating without hammering the pipe
Go outside and confirm water is actually leaving the discharge
Check the discharge outlet is clear of ice, soil, mulch and snow
Clean silt and gravel out of the bottom of the pit
Confirm the pump is plugged into a live receptacle, not a switched or shared one
Test the backup pump on its own float and check the battery condition

Questions

Sump Pumps, answered.

How often should a sump pump be replaced?

Rather than counting years, judge it on behaviour. A pump that starts on the first rise of the float, empties the pit, and shuts off cleanly is doing its job. A pump that hesitates, hunts, cycles rapidly, or needs the float nudged is telling you something. Test it every year before spring melt, and replace it on symptoms rather than waiting for the failure to pick its own timing.

Can my sump pump discharge into the floor drain or the sanitary sewer?

No. Groundwater going into the sanitary system is a large part of why mains surcharge during heavy storms and push sewage back into basements. Sump discharge belongs outside at grade, sloped away from the foundation. If your existing sump is connected into the sanitary, which we do still find in older houses, it should be corrected.

Why does my sump pump keep running when it has not rained?

Usually one of three things. A failed check valve lets the water in the discharge pipe fall back into the pit so the pump refills its own basin. A stuck or fouled float never tells the pump to stop. Or there is genuine groundwater arriving, from a high water table, a neighbouring downspout, or a broken water line. The first two are quick to check.

Do I need a battery backup sump pump?

It depends how much you would lose. Summer storms in the GTA take out power and drop a lot of water in a short time, and that is a bad combination if the basement is finished or holds anything you care about. A backup gives you hours of runtime, not indefinite protection, and the battery has to be maintained for it to mean anything.

My sump discharge froze last winter. What can be done?

Freeze-ups usually trace back to routing: an uphill run, a long exterior length, a low spot that holds water, or an outlet buried in snow. We look at slope so the line drains back after each cycle, shorten the outside run where possible, and can fit a removable winter extension or a relief opening so the pump has an escape route if the end does ice up.

How do I test my own sump pump?

Pour a couple of buckets of water into the pit and watch. The float should lift, the pump should start without hesitation, the pit should empty, and it should shut off without cycling back on. Then walk outside and confirm water is coming out of the discharge, clear of the wall. That last step is the one people skip, and it is where the problems hide.

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