How to build a pond waterfall: the natural stone project, from liner to pump

A waterfall transforms a pond: the sound of water, movement and oxygen supplied to the fish. And it is a project accessible to anyone willing to handle a few heavy stones. But it is also, by far, the leading source of leaks in a pond. Runoff finds the slightest defect, passes behind a stone, spills over an edge that is too low and seeps into the ground, even though the pond itself is perfectly watertight. A successful waterfall relies on a continuous liner beneath all the stones, raised edges along the entire course, a pump sized for the actual height and a well-positioned spill stone. Here is how to build it.

Step 1: designing the waterfall

Before picking up a shovel, ask yourself three questions. Where does the water start? Where does it fall? And from where will it be viewed? A waterfall is best positioned facing the terrace or a window, so you can enjoy its movement and sound. It should remain in proportion to the pond: a tall, narrow drop above a small pond will spray water outside and quickly lower the water level.

Several small steps often look more natural than one large drop, and each step can form a small intermediate pool that retains water when the pump stops.

Step 2: the slope and the steps

The soil removed during excavation is used to build the slope. It must be compacted layer by layer; otherwise, it will settle under the weight of the stones and deform the steps, resulting in overflow. Then shape each step with a slight back slope: the water remains on the step instead of running toward the edges.

Step 3: waterproofing, the decisive factor

The entire course of the water must rest on a liner laid over protective underlay. Ideally, the waterfall liner is the same as the pond liner or extends it. If you need to use several sheets, overlap them generously, with the upper sheet over the lower one, like roof tiles, so the water always flows over the joint.

Raise the liner edges on both sides of the course well above the water level: most waterfalls leak at the banks that are too low, where the water runs onto the soil. The edges will then be hidden by stones and plants.

Step 4: the spillway stone

Each drop rests on a flat stone that forms the waterfall's "lip." Choose stones with a sharp edge: the water separates cleanly and forms a curtain instead of clinging to the rock and running underneath. Set it level across its width, slightly overhanging the lower step, and wedge it securely. Behind and beneath this stone, fill all gaps with pond-grade expanding foam or mortar to force the water over the top. Around it, place larger stones that frame the drop and conceal the liner.

A common issue: the waterfall looks beautiful, but the water curtain disappears after a few days. The cause is almost always a poorly positioned spillway stone or an unfilled gap through which the water passes underneath.

Step 5: choosing the pump and hose

The flow rate stated for a pump is measured at zero head. As soon as the water has to be raised, the actual flow decreases, and the greater the height, the more it decreases. Therefore, consult the manufacturer's flow curve at the height of your waterfall, adding the losses caused by the hose length and bends.

A practical tip: choose a pump that is slightly more powerful than necessary and regulate the flow, rather than the other way around. An adjustable-flow pump lets you fine-tune the appearance without dismantling anything.

Step 6: bringing the water to the top

Insert the hose along the slope, outside the liner, and bring it out at the top into a hollow stone, beneath a flat stone, or into a preformed spring feature. Avoid piercing the liner: run the hose over its raised edge. A flexible spiral hose with a generous diameter limits losses and resists crushing under the stones.

Step 7: test before finishing

Before planting and putting on the finishing touches, run the waterfall for several hours. Mark the pond's water level and check that it does not drop beyond evaporation. Follow the water's path with your hand along the banks and watch where it flows. This is the time to raise an edge or reposition a stone, not once the planting is finished. Finally, plant ferns, sedges or marginal plants in the pockets between the stones to conceal the liner and give the cascade its natural appearance.

You might also like

To secure the stones without damaging the liner: How to glue the stones of my pond waterfall?.

READ THE ARTICLE

Frequently asked questions

— Why does my pond empty when the waterfall is running?

Most often, water overflows over a bank that is too low or passes beneath a stone and seeps outside the liner. Follow the water's path and raise the edges.

— Which pump should you choose for a pond waterfall?

A pump whose flow remains sufficient at the height of your waterfall, based on the manufacturer's curve. A slightly oversized, adjustable model offers greater flexibility.

— Is a liner needed beneath the entire waterfall?

Yes, along the entire watercourse, laid on underlay, with sheets overlapping in the direction of flow and raised edges.

— How do you create a beautiful water curtain?

With a spill stone featuring a sharp edge, set level with a slight overhang, gaps filled and sufficient flow for the width.

In summary

• Draw the waterfall to scale with the pond, facing the viewpoint.
• Compacted slope, steps sloping backward.
• Continuous liner on underlay, sheets overlapping like tiles, edges raised.
• Spill stone with a sharp edge, secured in place, with gaps filled.
• Pump selected according to the flow-rate curve at the actual head, with generously sized tubing.
• Test for several hours before planting.

Last updated: September 29, 2026.