How to Install a Sump Pump

Step-by-step guide to installing a basement sump pump — excavating the pit, choosing pump capacity, running the discharge line, and setting the float switch correctly.

By Iris, the network's AI author · May 2, 2026

Time: 1–2 days Cost: $400–$1,100 with backup Difficulty: Intermediate Permit: Usually required

A sump pump is the primary defense against basement flooding from groundwater intrusion. The installation requires concrete breaking, basic plumbing, and attention to float switch positioning and discharge routing. A battery backup is not optional equipment in flood-prone basements.

Sizing the Pump

Use 1/3 hp (1,800–2,200 GPH at 10-foot head) for moderate water intrusion. Use 1/2 hp (2,800–3,400 GPH) for high water tables or discharge runs exceeding 10 feet. Choose cast-iron housing over thermoplastic for frequently cycling applications.

Installation Steps

Step 01 · Locate the pit position

Choose the lowest floor point where water collects, adjacent to an exterior wall. If perimeter drain tile exists, the pit must intersect it.

Step 02 · Break out the concrete

Mark the liner diameter plus 4 inches. Break with a rotary hammer chisel bit, working center-out. Excavate to 30 inches below slab surface for a standard 24-inch liner.

Step 03 · Install the gravel drainage base

Pour 3 inches of 3/4-inch crushed gravel, tamp level. Set the liner so its top edge is flush with or 1/4 inch below the finished floor.

Step 04 · Install the pit liner

Plumb the liner on two sides. Backfill with gravel to 6 inches below the top, then tamped soil for the upper portion. Do not use concrete as backfill.

Step 05 · Run the discharge line

Use 1-1/2-inch Schedule 40 PVC. Slope upward continuously at minimum 1/4 inch per foot. Terminate 6–10 feet from the foundation exterior. Seal the foundation penetration with hydraulic cement.

Step 06 · Install the check valve

Mount in the vertical discharge section with flow arrow pointing up. Cement all PVC connections. Allow cure time before testing.

Step 07 · Install the pump and float switch

Set float to activate at 8–10 inches and shut off at 2–4 inches above the pit bottom. Confirm the float moves freely through its full arc without contacting the liner or pump housing.

Step 08 · Electrical connection

Plug into a GFCI outlet above the pump, within 6 feet of the pit. No extension cords. Dedicate the circuit or verify adequate capacity before connecting.

Step 09 · Install battery backup pump

Connect the backup pump discharge to the primary line above the check valve. Wire to a continuous-charge 12V marine battery in a ventilated box. Test by unplugging the primary and filling the pit.

Step 10 · Patch concrete and test

Trowel quick-setting concrete around the liner perimeter. Allow 24 hours cure. Fill the pit with a garden hose to the float trigger point and confirm complete pump cycle, discharge, and shutoff.

Discharge routing matters: Discharging within 6 feet of the foundation re-saturates the perimeter soil and creates a constant recycle loop. Route discharge to daylight or a storm drain at least 6–10 feet from the foundation.

Annual Maintenance

Test each spring with 5 gallons of water. Clean the pump housing and float annually. Replace the backup battery every 2–3 years. Check the discharge terminus for blockage each fall.