Plan the perfect garden with our interactive tool →

How to Build a Sump in a Garage

Sump pumps are an important device in protecting your property from flood damage. They collect groundwater into a reservoir, then transport the water away from the structure with a pumping mechanism powered by either electricity, water, or battery. Most homes at risk for flood damage keep sump pumps in the basement, but some homes require a sump pump for the garage as well. Although building a sump pump for your garage takes some basic construction knowledge, it can be accomplished by following a few steps.

Building a Garage Sump Pump

Step 1

Choose the appropriate location for the sump in your garage. It should be placed at least 10 inches away from the sides of the garage (to be sure it's clear of the foundation wall and/or footer) and near enough to its power source. Do not place the sump near an area where cars will be parked.

Step 2

Outline the sump basin at the widest part with a marker. Using electrical tape, mark a square that extends about 10 inches wider than the perimeter of the basin on each side.

Step 3

Wearing your safety goggles, break through the concrete with a jack hammer by cutting along the lines of the electrical tape. Use a flat, spade-type jack hammer head for the perimeter cuts. If desired, switch to a pointed head for breaking up the interior of the cutout. Slice multiple lines within the perimeter of the square to break down the concrete into easily removable pieces. Extract the chunks of concrete from the square. You may need heavy-duty wire cutters or bolt cutters to cut through wire mesh within the slab; if you run into rebar, cut through it with a reciprocating saw.

Step 4

Assess how deep to dig the sump by measuring the sump basin. Use your spade to dig a hole within the perimeter of the square. Place the basin in the hole to ensure its top edge is level with the garage floor slab.

Step 5

Surround the basin with filter fabric before lowering it into the hole. Place about 3 inches of gravel inside the basin, then place some more gravel around the exterior of the basin.

Step 6

Mix concrete following the manufacturer's directions. Fill the hole around the outside of the basin until the concrete is level with the surrounding slab. Smooth the surface of the wet concrete with a trowel. Allow 24 hours for the concrete to set.

Step 7

Tape the electrical cords of the pump to its discharge pipe with electrical tape. Attach the check valve to the end of the discharge pipe and tighten the clamps with a screwdriver.

Step 8

Place a stone paver inside of the basin over the gravel. Rest the sump pump on top of the paver inside the basin.

Step 9

Determine where to drill a hole in the siding of your garage to allow the liquid to be pumped outside. The water should be relocated to an area where it will flow away from the home.

Step 10

Drill a hole large enough to accommodate PVC piping in the siding of the garage, using a drill and hole saw. Determine how much PVC pipe will be required to run from the check valve of the sump pump to the outdoor discharge location.

Step 11

Attach PVC pipe to the check valve of the sump pump using PVC cement. Continue adding PVC pipe extensions and fittings as needed to run through the hole in the siding and out to the discharge point. Caulk around the pipe where it runs through the wall and let the caulk dry as directed.

Step 12

Power your sump pump by either plugging it in or utilizing whatever power source is specific to your model. Test the pump following the manufacturer's directions.

Garden Guides