How to Waterproof With Interior Drain Tiles

Break up and remove concrete around the perimeter of the floor slab where the drain tile will be placed. A jackhammer will typically prove ideal for this task, but a concrete saw or other tool may be used. Only break up and remove concrete from the slab. Avoid damaging the footing, which must be intact to support the wall.

Excavate a trench along the perimeter where the concrete was removed using a mattocks, hand spade or other utensils. Dig the trench next to the footing and make it about 4 to 6 inches deep. Take into account the depth and location of the sump pit and any inlet on the sump basket that the drain tile must reach, as the drain tile must slope slightly towards the sump pit.

Drill a series of weepholes along the base of the wall if the wall is made up of concrete masonry units or is otherwise hollow. Use a rotary hammer with a 3/8-inch bit and drill through the wall surface until the hollow space or center of the wall is reached. Water may pour out of the weepholes immediately.

Line the excavated trench with filter fabric. The fabric will keep sediment out of the drain tiles and prolong the drain's functional life.

Place about an inch or two of clean, coarse gravel in the trench. Spread the gravel out in the trench so it maintains the slight slope towards the existing sump pit or other outlet.

Lay the drain tile atop the gravel in the trench. Ensure that it extends to the sump basket and use a connector, if needed, to attach the drain tile to an inlet. Make sure that the drain tile slopes slightly toward the sump system.

Fill in the space on either side of the drain tile with gravel.

Cover the gravel and drain tile with filter fabric.

Place a plastic or metal weep flange along the trench or footing so it extends up the wall. A weep flange is designed to leave a small gap between the material and the wall so any moisture penetrating the wall can enter behind the flange.

Fill most of the remainder of the trench and excavated area with gravel. Leave only enough space to accommodate the concrete patch.

Apply concrete patch to the graveled top of the trench with a trowel. Mix and lay the patch according to specific manufacturer instructions. Only a small portion at the top of the vertical part of the flange needs to remain uncovered by the patch.