Crawlspace Sump Pump: What You Should Know?

Written By Adam Paul - Waterproofing Expert

A crawlspace sump pump is a submersible pumping device installed in the lowest point of a building’s crawlspace. sump pumps are mainly of 5 types, among them, submersible sump pumps and battery-powered backup sump pumps are the most suitable for crawlspaces. The main purpose of using a sump pump is to remove standing water in the crawlspace due to seepage and leaks caused by heavy rain, high water tables, or pipe leaks, reducing the risk of flooding inside the crawlspace.

A crwlspace sump pump works mainly in 3 steps, including water collection, pump activation, and discharging water. The standard size of a crawlspace sump pit is typically 18 to 24 inches deep and 14 to 18 inches in diameter. The crawlspace sump pump should be located at the lowest point of the crawlspace where water naturally collects. 1/3 horsepower (HP) sump pump is the ideal size sump pump for the mid-size crawlspace. It can handle up to 2,000-2,500 gallons per hour (GPH) at a 10-foot lift, which is sufficient for average water infiltration in residential crawlspaces.

You should follow the proper steps when installing a sump pump in the crawlspace. As well as crawlspace sump pump should be maintained properly to remove the excess water away from the crawlspace. If the sump pump is not working properly, you should check the following 6 common ways. As waterproofing experts, Aqviz highly recommend you install a proper crwlspace sump pump and maintain it for a water and damp-free crawlspace.

What is a Crawlspace Sump Pump?

A crawlspace sump pump is a submersible pumping device installed in the lowest point of a building’s crawlspace. The primary role of the sump pump is to collect and discharge water that accumulates in this confined area due to poor drainage, plumbing leaks, or groundwater infiltration.

Crawlspace sump pump helps to remove the accumulated water inside the crawlspace and control the dampness. It prevents condensation, mold and mildew growth, musty and stale odor, wood rotting, wood warping, corrosion, and other water damages in the crawlspace.

What are the 5 types of Crawlspace Sump Pumps?

There are 5 main types of sump pumps used in crawlspaces, each designed for different performance needs and installation conditions.

Submersible Sump Pump: A submersible sump pump is a fully enclosed unit designed to sit inside the sump pit, and it is completely submerged in water.
Pedestal Sump Pump: A pedestal sump pump is a type of sump pump where the motor sits above the sump pit while the intake pipe extends down into the water.
Battery-Powered Backup Sump Pump: A battery-powered backup sump pump is a secondary sump pump that activates when the primary sump pump fails due to power outages or mechanical failure.
Water-Powered Backup Sump Pump: A water-powered backup sump pump is an emergency pump that operates using water pressure instead of electricity or batteries.
Combination Sump Pump System: A combination sump pump system integrates a primary sump pump (either submersible or pedestal) with a backup pump (battery-powered or water-powered) in a single unit.

Among them, submersible sump pumps and battery-powered backup sump pumps are the most suitable for crawlspaces. Submersible units are compact and sealed, making them ideal for tight spaces and wet environments. Battery-powered backups are essential in case of power outages, which often occur during heavy storms when the pump is needed most. In crawlspace waterproofing projects, we often recommend a combination of these two for continuous protection and reliable performance.

Why should you use a Crawlspace Sump Pump?

Using a crawlspace sump pump provides long-term protection against moisture-related issues that threaten both the structure and health of a home. You should install a sump pump in the crawlspace due to these reasons.

The sump pump removes standing water caused by heavy rain, high water tables, or pipe leaks, reducing the risk of flooding inside the crawlspace.
Sump pumps lower overall humidity levels, protecting insulation and HVAC systems in the crawlspace.
Crawlspace sump pumps help to prevent fungal spores from spreading into living spaces.
A sump pump helps avoid wood rot, warping of joists, rust on metal supports, and degradation of concrete footings in the crawlspace.
Sump pumps improve indoor air quality in the crawlspace.

How does a Crawlspace Sump Pump Work?

A crwlspace sump pump works according to these 3 main steps.

Water collection: Water enters the sump pit through drain tile systems or natural flow from the crawlspace floor. The pit is strategically placed at the lowest point to collect maximum water from the surrounding area.
Pump activation: When the water level in the pit rises to a set point, a float switch triggers the sump pump to turn on.
Water discharge: The pump pushes the collected water through a discharge pipe, directing it safely away from the foundation to a storm drain, dry well, or designated drainage area, preventing re-entry into the crawlspace.

What is the size of the Crawlspace Sump Pit?

The standard size of a crawlspace sump pit is typically 18 to 24 inches deep and 14 to 18 inches in diameter. This size is adequate to collect a sufficient volume of water while fitting into the limited clearance and confined space of a crawlspace or underfloor cavity.

The sump pit should be large enough to allow the sump pump to operate efficiently without short-cycling, but compact enough to suit the narrow access typical of crawlspaces. Using a durable, perforated plastic basin with a sealed lid helps manage sediment and vapor while maintaining clean water intake. Proper sizing ensures better pump performance and extends the life of the system.

Where to Locate a Crawlspace Sump Pump?

The crawlspace sump pump should be located at the lowest point of the crawlspace where water naturally collects. This ensures maximum water drainage by using gravity to direct moisture toward the pump basin. If the crawlspace has uneven grading, use a level or slope the area slightly toward the selected location to improve water flow.

You should avoid placing the sump pump near HVAC equipment, plumbing connections, or load-bearing supports to ensure easy access for maintenance. For best performance, install the sump pump near an exterior wall to minimize the discharge pipe length and reduce backflow risks. The discharge outlet should lead water at least 10 feet away from the foundation to prevent re-entry into the crawlspace.

What Size Sump Pump is needed for a Crawlspace?

For most crawlspaces, a 1/3 horsepower (HP) sump pump is the ideal size. It provides enough power to handle up to 2,000-2,500 gallons per hour (GPH) at a 10-foot lift, which is sufficient for average water infiltration in residential crawlspaces.

If the crawlspace is larger than 1,500 square feet, or the area has a high water table, frequent flooding, or long discharge runs, upgrading to a 1/2 HP pump may be necessary. Always consider the vertical lift height, horizontal discharge length, and the volume of water entering the pit. Oversizing can cause short-cycling, while undersizing leads to water backup. Choose a pump rated for continuous duty with a reliable float switch for consistent performance.

To determine the sump pump size you can use this sump pump calculator.

How to Install a Sump Pump in Crawlspace?

You should follow these 6 steps when installing a sump pump in crawlspace

Choose the lowest point: Identify the lowest section of the crawlspace where water naturally collects. This is the ideal location for the sump pit.
Excavate the sump pit: Dig a hole approximately 18-24 inches deep and 14-18 inches wide in the crawlspce area. Use a durable plastic or perforated sump basin to hold the pump and allow water entry.
Install drain tile (optional but recommended): For better water collection, lay a perforated drainage pipe around the crawlspace perimeter, sloped toward the pit.
Place the sump pump: Set the pump inside the sump pit, ensuring the float switch moves freely. Submersible models are preferred for limited clearance.
Connect the discharge line: Attach a PVC pipe to the pump outlet and extend it to a safe drainage location at least 10 feet away from the crawlspace.
Seal and test the system: Backfill around the basin with gravel, cover with a lid, and test the pump by filling the pit with water to trigger activation.

How to Maintain a Crawlspace Sump Pump?

Here are 6 essential ways to maintain a crawlspace sump pump properly.

Inspect the sump pump every 3-4 months
Clean the sump pit from dirt, gravel, and debris
Test the float switch for smooth operation
Check the discharge line for clogs or freezing
Examine the power source and backup battery
Service the pump annually by a professional technician

Why does a Crawlspace Sump Pump not Work Properly?

Here are 6 common reasons why a crawlspace sump pump may stop working properly

Clogged or blocked sump pit or intake screen
Malfunctioning or stuck sump pump float switch
Broken check valve in the discharge line of the sump pump
Power failure or disconnected power supply of the sump pump
Damaged or worn-out motor sump pump components
Frozen or obstructed discharge pipe of the sump pump

Can I use a Basement Sump Pump in Crawlspace?

Yes, you can use a basement sump pump in a crawlspace, but it must be suitable for the confined conditions of the underfloor area. Not all basement sump pumps are designed for low-clearance spaces. For crawlspaces, submersible models are more appropriate than pedestal types, which require vertical clearance and are typically too tall for tight voids.

When selecting a basement sump pump for crawlspace use, ensure it has a compact design, sealed motor, and durable housing to withstand moisture and sediment.