How to Build a Concrete Sump Pit
- 1). Dig a hole a minimum of 24 inches wide and 27 inches deep. The hole can be larger and deeper, but this size will give you a finished pit of 18 inches wide by 24 inches deep. This will work very well with almost any brand or style of sump pump you may install. The sides of the hole need to be free of any obstructions such as stones or tree roots. You will also want a smooth surface so you get a uniform concrete thickness throughout the pit.
- 2). Build a frame to fit inside the hole so when it is inserted there will be 3 inches of open space on all sides. Build the frame 3 inches shorter than the depth of the pit. Example: If your hole is 27 inches deep, make the frame 24 inches in height. Build the frame sturdy; if it should fail, the clean-up would be messy as well as time consuming.
- 3). Use the wheelbarrow to mix the cement. With the frame out of the pit, pour in enough cement to cover the base of the pit with 3 inches of concrete. Allow this to sit for a short time, no more than 30 minutes, then carefully put the wooden frame into the pit. Keep the frame centered and level as you pour the remaining concrete around the outer edges. Bring the concrete up level with the existing floor. You will then need to pack the concrete down to eliminate any air pockets and smooth it out to a nice finish.
- 4). Allow the concrete to set for a minimum of 24 hours before removing the frame. Once the frame is removed, the concrete should be allowed to sit undisturbed for another 48 to 72 hours. After that time, the pit is ready for use.
Source...