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  • Writer's pictureJohn@LiteHouse

How Sump Pumps Work

Sump pumps are self-acting electric pumps that protect houses from moisture penetration. They are usually installed under basement floors or floors to remove rising groundwater and surface runoff before it has a chance to seep into the home. Accumulated water can cause interior damage and encourage the growth of mold, mildew and fungus. Pumps should be maintained and equipped with all necessary parts to ensure their reliability.

How a sump pump works

A pit, known as a sump or sump ditch, can be dug in the lowest part of the basement floor to catch and contain any runoff. A sump pump is located at the bottom of this trench (or next to it) and pushes the excess water through a series of interconnected pipes to a suitable discharge point. The pump can sense the water level via a float that rises and falls as the water level in the trench fluctuates. The sump pump activates and deactivates based on float height, providing a simple, automated way to monitor and deal with fluctuating water levels.

Types of sump pumps

Stand-alone sump pumps are located above the water level next to the sump and are not designed to get wet. Since they are not contained in a sump, they are easily accessible, but they are also very noisy. They cost around $60 to $200, which is significantly less than other varieties.

Submersible sump pumps rest underwater at the bottom of the sump and are much quieter than stand pumps. Their oil-cooled motors and tight seals protect against water and dust and give them a long life. They can cost up to $600.

Water-powered sump pumps are commonly used as a backup and are activated when the main pump experiences an electrical or mechanical failure.


The pump must be kept clean and free of dirt. The inlet screen prevents dirt and other solid material from entering the pump, but can clog the pump. Cleaning should be done frequently for pumps that run continuously.

Inspectors should make sure the float is not tangled or stuck in one position. A sump pump with a stuck float is useless because it won't know when to turn on and off.

The pump can be tested by pouring water into the sump to make sure it activates and pushes water out. The homeowner should seek professional help if the pump does not activate.

Maintenance should take place annually and when the house is sold.

No one should ever reach into the pit when testing the pump. A household object such as a golf club (with a rubber grip) or anything else non-conductive that happens to be lying around can be reached and manipulated on the float.

Inspectors should check for the presence of the following:

GFCI. There is considerable debate among inspectors as to whether or not a sump pump should be connected to a GFCI. It is possible that a GFCI can prevent electrocution, but it is extremely unlikely that the sump pump would feed the water first. A GFCI is much more likely to trip under safe conditions and disable the sump pump when needed. A sump pump is among the most critical of all household appliances, and disabling it, especially when the tenants are not home, could cause catastrophic damage to the building. Codes recommend that equipment in basements and crawl spaces be connected to a GFCI to reduce the risk of electric shock, but this advice is often ignored due to concerns about nuisance tripping.

Alarm. Sump pumps can burn out, lose power, clog or misalign, or fail in many other ways. It is valuable to have a warning device installed that will signal the accumulation of water. These alarms can alert homeowners or neighbors of flooding so that it can be addressed before water damage occurs. Alarms are especially important in residences that are not occupied for long periods of time. Inspectors should keep in mind that while an alarm can be helpful, it is not a requirement.

Check valve. This device is the same diameter as the discharge pipe it fits into and is usually a different color. A check valve should be installed to prevent pumped water from the discharge line from re-entering the sump when the equipment is turned off. Without this valve, the pump will have to work twice as hard to remove the same column of water, causing unnecessary stress on the pump components. A check valve can also prevent the rare but worrisome possibility that a discharge line connected to a stream or pond will siphon back into the sump.

Backup power source. Power outages most often occur during heavy rains and floods, which are the situations when a sump pump is most needed. For this reason, combined with the inconvenient GFCI shutdown, sump pumps should have a backup power source that can be relied upon. A pump powered by a battery or domestic water pressure can also be installed as a backup. Installation of a back-up source or a back-up pump is not a requirement, but can be offered to the client as a recommendation.

That a pit that is big enough for the pump. The sump need not be made of any particular material as long as it is strong and provides permanent support for the pump. However, it must be large enough to allow the pumping room to function properly. Some homeowners use a 5-gallon bucket as a sump, but this is insufficient. For most homes, the sump should be no less than 24 inches deep and 18 inches wide. One of the most common reasons sump pumps fail is that the float gets stuck between the pump and sump because the sump is too tight.

Cover. The sump should be covered to prevent water from evaporating into the house.

Discharging Water

LiteHouse Inspect inspectors are not required to check for the correct discharge location. They may notice a improper discharge if they see one, but looking for a discharge outside is not recommended. The following is good general information to give to the homeowner:

  • Water must be discharged at least 20 feet from the building.

  • The water should not drain back into the house! Circulating water puts unnecessary strain on the pump and can weaken the foundations of the structure.

  • Water should not drain onto a neighbor's property without his consent.

  • Many jurisdictions do not allow water to be pumped into public sewer systems.

  • Pumped water should never drain into the residence's septic system. Especially during heavy rain, the septic drainage field will become saturated and will struggle to handle the normal flow of water from the house. Additional water from the sump pump can damage the septic system.

In short, sump pumps are used to remove excess water from households that would otherwise cause property damage. There are several types, but all monitor the water level and ensure that it does not rise higher than a predetermined level. Proper maintenance and inspection

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