Adding a water feature such as a waterfall to your backyard or pool area creates a fresh, tropical feel and is soothing with the sound of the running water. While real rock is often used to create waterfalls, fake rock is also suitable, and has the advantage of being cheaper and lighter while still looking authentic. If your waterfall isn't part of a backyard swimming pool, rather a stand-alone feature, then you will also need to incorporate a small catchment pool into your waterfall design so that the water from the waterfall can circulate.
Dig a hole about 1 foot deep and 3 feet across for your catchment pond. Make a small channel in the side of the pond, near where the waterfall structure will be, around 1 inch wide. This is to hide the pump hose.
Line the pond with the pond liner, placing a few river stones around the edge to hold the liner down. Make sure the channel for the hose is still accessible.
Lay the pump hose along the channel with the end protruding 3 or 4 inches into the pond hollow with the remainder leading to where the pump will go.
Arrange the largest rocks on the edge of the pond to form the base of the waterfall. When building the waterfall, think of the shape as a more of a pyramid, rather than a rectangle or tower. Create ledges at different levels where the water can pool before flowing over--you can buy fake rocks with a concave top specifically for this purpose. Remember that the front of the waterfall is not the only side visible, you are creating a 3D structure, rather than a wall.
Attach the pump to the end of the pond hose then attach the waterfall hose. Thread the waterfall hose through the centre of the pile of larger stones, and continue laying more stones, making sure the waterfall hose continues up through the middle of the rock pile. Every couple of rocks, take a step back and evaluate the look of the waterfall from all sides before continuing.
Lay stones laterally so it looks like a natural rock shelf rather than a rock tower, then test the flow of the water by putting the garden hose end where the end of the waterfall hose is and turning it on. Adjust the position of any rocks that are obstructing the flow, or if the water is not properly flowing into the catchment pond.
Cement any rocks that are a bit unsteady only once the waterfall is how you want it. Refer to the cement mix directions for appropriate curing time. Use an easy-mix cement designed for use in home and gardens. A waterproof cement is not necessary so long as you give the cement adequate time to cure before turning the pump on. The water will not affect the bonding capacity of the cement once the cement is cured.
Fill the catchment pond with water then turn on the pump.
If the water shoots upwards, instead of trickling down the waterfall, place a small river stone over the opening of the waterfall hose. This will make the water flow properly. Plants around the edge of the pond, and even on small ledges in the waterfall help to make the whole design look natural. Fish can be added to the pond, so long as you use a pump with a filter, and there are no dangers from predators such as birds or cats.