How to Build a Garden Stream: Pre-Formed Units Installation Guide

Installing a Pre-Formed Stream

Pre-formed stream units link together in various configurations. They're watertight when correctly installed but need careful positioning to look natural.

Creating a Layout

Lay out units first to achieve the desired effect. A stream should start logically — ideally as a bubbling spring. Use a sunken container (e.g., old dustbin) filled with large stones, fed by the pump hose, disguised with rocks and plants. Or build a header pool at the top with the pump outlet concealed among planting.

If the stream head is far from the pump, a powerful surface pump and permanent piping are needed. For submersible pumps, keep the head within easy reach of the pool; use shrubby planting to separate visible features. A rock garden abutting the pool can integrate the header naturally. A cascade can also serve as the stream's start.

Digging Out

Mark the run with pegs, excavate the entire bed with a fall toward the pump. Include any pools. Ensure side-to-side level with pegs, board, and spirit level. Excavation should be 15 cm (6 in) longer/wider and 7.5 cm (3 in) deeper than units for sand bedding and adjustments.

Achieving the Correct Gradient

Best gradient: 10–30 degrees. Water can run directly to the pool or be slowed by shallow waterfalls and small pools (intervening sections nearly flat). Speed up flow in places by narrowing the stream with rocks after construction.

Set pegs with level tops first to read existing ground levels. Then knock each successive peg down for the desired fall angle. Use a wooden set square for accuracy. Adjust soil so each peg protrudes equally — this simplifies excavation.

Installing Stream Units

Build from the pool backward — not from the header. Remove stones/roots, spread damp builder's sand evenly. Ensure watertight overlaps between units. Check level side-to-side, bed firmly, backfill with soil.

Disguise ugly edges with rocks and plants. Cover the bed liberally with washed stones — no plastic/fibreglass should show.

Using Sectional Units

Sectional units connect with sealant and include height adjustment panels — invaluable on slopes to maintain water levels in each component when the pump is off. They also allow more natural sweeping curves.

Step-by-Step: Installing Pre-Formed Stream Units

1. Measure with pegs, excavate 15 cm longer and 7.5 cm deeper than units.
2. Ensure side-to-side level and gentle bottom slope.
3. Line with builder's sand bedding; some units have height adjustment panels.
4. Position sections carefully — level, firmly embedded; may take several attempts.
5. Disguise edges with stones, cover bed with decorative pebbles. Cement edging stones for security.
6. Plant streamsides with moisture-lovers; remember the stream is waterproof and won't dampen surrounding soil.