A pool pump is subject to constant pressure from the flow of water passing through the unit. If not anchored securely, this pressure can cause enough motion to move the pump, stressing the connections and possibly causing damage. Anchoring the pump directly into the ground isn't an option due to shifting soil, and a wooden base is subject to the expansion and contraction caused by temperature changes that would eventually loosen any bolts holding the pump in place. A cement pad however, has both the strength and stability you need to secure the pump, while being simple enough to build that no previous experience is necessary for completion of the project.
Mark the parameters of the slab on the ground using wooden stakes placed at the slab corners. Set the stakes so they outline a square measuring 2 feet, 2 inches, on each side. Attach a string to the top of the stakes with a thumbtack, connecting the four stakes in the square so that you can check the angles of each corner. Use a carpenter’s square to make certain each corner forms a 90-degree angle.
Dig a hole for the foundation of the pad 4 inches deep using a spade. Compress the floor of the hole with a tamper to create a sturdy base of soil for the concrete.
Cut two of the boards 2-by-4 boards 2 feet in length and the other two 2 feet, 4 inches, long. Nail the boards together to create a square measuring 2 square feet internally. Use 16d nails for the joints of the square, creating a form that’s 4-inches in height. Place the form into the cleared foundation hole.
Place a carpenter’s level across a 2 by 4 on top of the form to check for level. Adjust the form’s position until the top of the form is level by tapping high points of the form into the soil at the bottom of the hole with a hammer.
Fill the bottom of the form with 2 inches of gravel. Tamp the gravel down to compress the material. The gravel will aid in drainage beneath the slab, preventing sagging of the slab due to saturated soil beneath.
Add water to the dry cement mix in a wheelbarrow, and fold the water into the mix with a hoe until the cement is the same consistency as a thick batter.
Place small concrete blocks about 2-inches square into the base of the hole to hold the wire mesh in place in the center of the slab. Line the base of the hole with the blocks, spacing them out every six inches throughout. Cut the wire mesh with tin snips to fit the interior of the form, leaving 2-inches on each edge to avoid exposure to air or soil after the concrete is poured.
Pour the cement into the form through the mesh until it reaches the top of the form boards.
Drag a screed across the top of the form to remove any excess cement. Use a sawing motion back and forth across the form top while moving the screed. Smooth the poured cement by running a floater across the cement surface. Tap the sides and top of the form with the floater to cause any air bubbles within the cement to float to the surface.
Wait for the water that surfaced while floating the concrete to be reabsorbed into the slab and then float the slab a second time, drawing moisture to the surface once again. Cover the concrete with a plastic sheet weighed down on the ground on the edges with bricks or stones to hold the sheet in place. Remove the sheet daily for two to four days, and spray the concrete with a light misting of water from a hand mist sprayer to prevent its drying out as it cures.
Remove the sheet, and allow the slab to continue curing for 10 full days before attaching the pool pump.