When you attempt to repair an in-ground pool wall, proceed with caution; in-ground pools are subject to a phenomenon known as hydrostatic pressure. This means the ground water accumulated around the outside of a pool's walls can exert greater pressure on an empty pool than the pool's concrete walls can exert back on it, causing the pool walls to crack or even collapse when it is drained. Only attempt to repair minor holes or cracks yourself; consult a professional for pools that show signs of extensive or structural damage.
Remove all items from the pool, including the vacuum creeper and toys or recreational items like floating chairs.
Turn off the filter and the pool's heater.
Place a sump pump on the pool deck near the shallow end of the pool. Set the siphoning hose in the pool and drain the pool to just below the level of the damaged area. If the damage is more than halfway down the deep end of the pool, do not attempt to repair the damage yourself. Call a professional pool repairman.
Turn the sump pump off and remove the siphoning hose from the pool. Set the sump pump aside.
Unpack the pool repair kit. Mix the thickening activator with the included liquid rubber, following the manufacturer's instructions. Apply the patch medium to the damaged area of the pool wall with a putty knife. Fill the crack or hole entirely. Spread the patch mixture another 6 inches around the edges of the actual crack/hole on the pool's wall. Smooth to even the patch's edge with the wall surface; let it dry for 12 to 24 hours, or as long as directed by the packaging.
Brush a thick coat of pool epoxy over the patched area using a paintbrush. Allow it to dry thoroughly and according to the manufacturer's instructions; this can sometimes be for as long as 7 to 14 days.
Place a garden hose in the shallow end of the pool once the patch has dried sufficiently and refill the pool. Turn the filter and heater back on.