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Failure of sump pumps

By Martin Morissette, P. Eng., NAFI-CFEI, CVFI

Many homes may have one or more sumps built in the floor of their basement. The main function of these sumps is to collect water from the surrounding foundation drain, the floor drains and garage dirt traps. The sump typically has a limited capacity (up to 200 liters) and can therefore be filled quickly during heavy rain or snowmelt. The electric pump is the device of choice for emptying the sump.

Figure 1
Pompe puisard figure 2 (002)2 Figure 2

The two most widely used types of pumps are the « submersible » pump and the « column » pump. Each one of these models has its advantages and disadvantages, which can strongly influence the choice of the homeowner. The submersible models (Figures 1 and 2, two similar models) are generally more expensive, being more robust and compact. This type of pump has the advantage of being completely hidden in the sump, being less cumbersome, but its motor is more vulnerable to water intrusion due to its submerged condition.

In contrast, the column model motor is located outside the sump and is not in contact with the sump water (Figure 3). However, this type of pump, which is generally more expensive to purchase, has a design that is more vulnerable to mechanical failure.

Figure 3

The following are the most common failures for these two types of pumps:

  • Presence of debris in the sump and its accumulation at the pump inlet, under suction, blocking or limiting proper water flow to be pumped, which can lead to sump overflow. Pebbles can also get into the impeller and cause damage;
  • Failure of the electric motor or its bearings;
  • Failure of the float switch or its fastening components;
  • Failure of the rotating shaft, typically made of plastic material (especially for the column type pump);
  • Failure of the impeller, although less frequent;
  • Misuse. Careless handling can damage several components such as the float switch, the electrical cord or even the impeller housing. An example of a submersible pump in poor condition is shown in figure 4.
Pompe puisard figure 4 (002) Figure 4
Figure 5

An overflow of the sump can also be caused by the malfunction of one of the devices associated with the installation of the pump, such as:

  • Clogged outlet pipe;
  • Broken, clogged or missing check valve;
  • Movement of the float switch impaired by an obstacle in the sump;
  • Damaged or sticky mechanical joint at the pump shaft (dried-out sump);
  • Improper adjustment of the float switch cord;
  • Electrical supply failure;
  • Blockage from (ferrous) red ochre.

To conclude, some low-cost precautions can be taken in order to avoid sump overflow, namely installing a second back-up pump in the sump, which is connected to a different electrical circuit breaker than that of the main pump (Figure 5, pump configuration), or a booster pump powered by a battery. There is also a type of « emergency » pump operating on city water. These pumps are of rather low capacity and are not permitted everywhere.

Do not hesitate to contact us for any questions or concerns regarding a claim involving a pump installation!

Martin Morissette, P. Eng., NAFI-CFEI, CVFI
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