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The Rising Tide of Sump Pump Failures

May 30, 2019

Types of Sump Pumps

In order to understand how and why sump pumps fail, it is important that we first understand sump pumps themselves. There are a few different types of pumps, but the most common, and the ones we will be discussing, are submersible pumps and pedestal pumps.

Submersible pumps are smaller, more compact and designed to work underwater. This makes it possible to place them right inside the sump well. The other main difference is the switch. A submersible pump has a tethered float switch which can move in any direction (this will prove to be important later).

Pedestal pumps have a motor that stands above the sump well with the impeller located in the foot of the pedestal. They also have a vertical float switch which can only travel straight up and down with a guiding rod.

Common Causes of Sump Pump Failure

Sump pump failures can result in two potential outcomes: Fire and flood. Fire is a decidedly less common occurrence, however, when a sump pump does catch fire, it is a subrogatable loss. Fires usually involve pedestal pumps since the very nature of submersible pumps make it incredibly unlikely for one to ignite. A sump pump fire can be the result of many of the same things that can lead to a flood. The important difference is that a flood is considered a safe failure while a fire is an unsafe failure.

Debris Caught in the Impeller

The real issue here is not so much with the sump pump as it is the sump well. The problem being, sump wells aren’t clean. Dirt and debris of all kinds can wind up in the well – sometimes following a renovation project. If a piece of debris is just the right size, it can get sucked in through the inlet screen and jam the impeller. The float will still activate the switch and turn on the motor, but with the impeller unable to spin, water will continue to fill up the well and eventually flood the basement.

As part of a destructive examination investigation, I was running tests on a sump pump in our laboratory. After confirming that there were no electrical continuity issues, I connected it to power and listened to it run (you can tell a lot about a sump pump by the sounds it makes). In this case, the low hum told me that electricity was circulating through the motor but the impeller wasn’t rotating. I turned the sump pump upside down, unscrewed the bottom cover and tried to spin the impeller. It wasn’t seized but it was incredibly stiff. Looking closer, I could see a tiny wood chip caught between the impeller and the wall. I pulled it out with a pair of tweezers and the pump proceeded to perform as expected. This examination proved to be in favour of my client who was being pursued for negligence.

Improper Installation

One type of failure we see within this subset, generally involving submersible pumps, has to do with the float. The problem occurs when the free-ranging float drifts too close to the wall of the well and gets caught. This can happen in the upward or downward position. If it gets stuck in the upward position, it will run constantly. This creates a situation where the motor could overheat or electrical components could fail, diminishing the life of the pump in both cases. If it gets caught in the downward position, it simply won’t turn on regardless of the water level. Tethered float switches can also get caught on another pump in the well, which is something we are seeing more often. Having two pumps in a well is generally fine, and it might actually be advisable to have a backup pump. But, the well has to be suitably large and the installation needs to be done correctly – ideally by a professional – so the floats do not interfere with one another.

My most recent experience with this type of failure occured while I was assisting with a structural failure investigation – it just so happens that the basement also flooded. It was a beautiful new custom home, built on a very high water table, so it made sense that there were two sump pumps in the basement. Unfortunately, the well wasn’t large enough to accommodate both, and right away I could see that one of the tethers was caught against the wall. The second pump had also failed, but the cause of its failure was never determined as we were performing a structural failure investigation. However, it is likely that something had jammed the impeller since the well was full of debris from construction.

A different installation issue involving pedestal pumps is airflow, or lack thereof. Submersible pumps are surrounded by water which cools the motor. Since pedestal pumps have a motor situated above the water, they are cooled by the air flow around them. Without sufficient air flow, the motor can overheat. For example, in one basement, the sump pump was located inside a closet. At some point, several coats had fallen on top of the motor causing it to overheat and eventually start a fire. A subrogation claim was filed against the manufacturer who argued that the sump pump needs to breathe. I remind you, though, regardless of installation or, in this case coats surrounding the motor, an appliance is required to fail safely. Had a flood only occurred, subrogation might have not been successful. In this case, because a fire had occurred, settlement was reached.

Wear and Tear

As with all mechanical devices, sump pumps wear over time. Some failures can be ascribed to manufacturing defects, such as problems with the mechanical or electrical components, but if the pump is more than seven years old, age may be a factor. By the same token, any time there is a damage claim and the pump is not more than a few years old it is worth doing an investigation because it may have prematurely failed internally, whether due to a capacitor, centrifugal switch, high-temperature limit safety switch or float switch failure.

Here’s one example of an intermittent failure: Inside a float switch is a ball that moves back and forth to activate or deactivate the switch, and thus the motor. In one incident involving a particularly old sump pump, the ball had gone back and forth so many times throughout it’s service life that it was no longer round. It had worn itself down. So sometimes the ball would get caught in the upward position; sometimes in the downward position. It just so happens that one time, while caught in the downward position, the basement flooded. Of course, no component is immune to the effects of time, and age can cause anything to fail, from the float switch to the motor.

What to Do

While we prefer to attend the site ourselves, we understand that time is of the essence and that it may not always be possible. When attending a scene, get as much background information on the house and pump as possible. How old is the house? Have there been any renovations or changes? How is old the pump? Where was it purchased? Who installed the pump? Answers to these questions can prove crucial to our investigation and may indicate or help eliminate potential causes. When taking photographs, be sure to capture the sump pump while it’s still in the sump well. This can help us determine if improper installation was a factor. Finally, secure the sump pump.

When is Subrogation a Factor?

Any time a sump pump failure results in a fire, you have a subrogatable loss – but that is not the only instance. Water damage claims are on the rise, in terms of both the number of claims and the average cost of a claim. We find ourselves investigating more and more sump pump failures – often for the reasons outlined above, however, this is by no means an exhaustive list. Design deficiencies and manufacturing defects can result in failures. There are also instances of builders installing the wrong size pump, or installing the right pump incorrectly. Subrogation can also come down to the circumstances surrounding the failure. For instance, in a rented dwelling, a sump pump may fail because the landlord has failed to maintain it properly. Conversely, a tenant disposing of items in the sump pit can cause the pump to fail. In either case, one party’s actions have resulted in damage to the other’s property.

As common as they are, sump pump failures are by no means straightforward. However, years of experience and exposure to these types of failures allow us to quickly narrow down the potential causes and arrive at the correct conclusion.

[1] “Flood Watch: 5 Things to Know about Your Sump Pump.” CBC, 6 Apr. 2016, 6:30 AM ET,