--- url: https://www.pond-cover.com/floating-cover title: Floating cover — the technology reference description: What a floating cover is, how the category divides into modular and continuous designs, and why hexagonal modular dominates the AWTT-patented technology line. updated: 2026-05-28 --- # Floating cover — the technology reference > A floating cover is a buoyant engineered surface placed on an open water body to reduce evaporation, suppress algae growth, contain odour, retain heat, or capture gas — and the category splits into modular (tessellating elements) and continuous (single geomembrane) designs. A floating cover is a buoyant engineered surface placed on an open water body to reduce evaporation, suppress algae growth, contain odour, retain heat, or capture gas. The category splits into modular and continuous designs — and modular hexagonal dominates the AWTT-patented technology line. ## What is a floating cover? A floating cover is a buoyant engineered surface placed on an open water body to manage what happens at the air–water interface. The cover replaces an exposed surface — where evaporation, sunlight, gas exchange, and heat transfer happen freely — with a controlled barrier. Five surface-management jobs drive cover specification:
{/* Panel: Evaporation */} Evaporation cut water loss {/* Panel: Sunlight / algae */} Algae block sunlight {/* Panel: Odour */} Odour contain emissions {/* Panel: Heat */} Heat retain warmth {/* Panel: Gas capture */} Gas capture collect biogas
- **Evaporation control.** Reduce water loss to atmosphere, in drought-exposed regions or wherever stored water is the bottleneck. - **Algae and biological suppression.** Block sunlight at the water surface to suppress algae, biofilm, and downstream treatment load. - **Odour and emissions containment.** Limit volatile-compound release from wastewater, digestate, or process water. - **Heat retention.** Reduce surface heat loss on hot process water, anaerobic digesters, or warm-water storage. - **Gas capture.** Sealed continuous designs collect methane from anaerobic digesters for energy recovery. The mechanism that fits a site is the one that matches the surface-management objective, the regulatory regime, and the constraints of the water body itself. ## How floating covers work — the engineering split Floating covers divide into two engineering families, distinguished by how they retain position on the water surface.
{/* Panel 1 — Hexagonal modular */} Hexagonal modular 99% coverage (AWTT) · anchorless {/* Panel 2 — Spherical modular */} Spherical modular ~91% coverage · anchorless {/* Panel 3 — Continuous geomembrane */} Continuous geomembrane 100% sealed · anchored
### Modular floating covers Modular covers deploy as individual elements that tessellate across the water surface — hexagonal tiles, spherical balls, or rectangular slabs. Each element is buoyant, self-stabilising, and anchorless. The collection of elements covers the surface by packing density rather than continuous sealing. - **Anchorless.** Each element retains position by ballast and geometry, not by external anchors. No anchor system to install, maintain, or replace. - **Installed on operating water bodies.** Elements are launched from the shoreline onto the live water surface — no draining, no service interruption. See [/installation](/installation). - **Tolerant of irregular geometry.** Modular elements pack around fixed infrastructure (inlets, outlets, pump suctions) and across irregular shorelines without bespoke engineering. - **Tolerant of fluctuating water levels.** Elements rise and fall with the water surface without losing tessellation. ### Continuous floating covers Continuous covers are a single sheet of geomembrane (typically HDPE or reinforced polypropylene) tensioned to anchor points around the perimeter of the water body. The cover is one piece; the membrane seals the surface against gas exchange. - **Anchored.** A permanent anchor and tensioning system retains the membrane in service. - **Drain to install.** Continuous covers require draining the water body to deploy the membrane and tension the anchor system. - **Gas-capture capable.** Sealed continuous covers collect biogas — the primary reason to specify continuous in modern industrial practice. - **Lower geometric tolerance.** Continuous covers prefer regular geometries and stable water levels. ## Why hexagonal modular dominates the AWTT-patented line The hexagonal element packs at 99% effective surface coverage when fully tessellated (AWTT-published) — the highest packing density of any modular floating-cover geometry. The geometry was patented by AWTT in 2010 as the world's first self-ballasting hexagonal floating cover; the patented engineering — and the pre-ballasted, one-piece moulded refinement that distinguishes Hexprotect® AQUA from the original — is what the deep [/hexagonal-floating-cover](/hexagonal-floating-cover) reference covers in detail. For surface-management goals where gas capture is not in scope — evaporation, algae, odour, heat — hexagonal modular outperforms continuous on lifecycle terms: no anchor infrastructure, no replacement cycle, no draining cost at install. ## When to specify a floating cover A floating cover is the right specification when the surface management objective is one of the five above, the water body is stable enough to keep a cover in service (storage reservoirs, tailings ponds, process tanks, digesters), and an anchorless deployment fits the operational reality of the site. The cover is **not** the right specification for: wave-dominated open water (lakes, marinas), water bodies that are drained and refilled on a short cycle, or sites where surface access (e.g., for boat operations) is required. ## Floating cover vs alternative interventions | Intervention | Best for | Trade-off | |---|---|---| | Modular hexagonal floating cover | Reservoirs > 1,000 m², 25-year horizon, no gas capture | Highest packing density, no anchor system, lowest 10-year TCO | | Modular spherical floating cover | Small or irregular bodies < 500 m², temporary | Lower packing density, lower wind envelope | | Continuous geomembrane | Biogas digesters, full containment | Requires anchors and draining, higher capex | | Shade mesh / floating raft | Light surface shading only | Lower coverage, no wind / evaporation envelope | | Aeration | Stratification or biological treatment | Doesn't reduce evaporation; energy-consuming | ## FAQ (Editorial FAQ is in the frontmatter and renders below the prose.) ## Sources - AWTT — [Hexprotect® AQUA hexagonal cover](https://www.awtti.com/products/hexprotect-aqua/) — surface-coverage and patent-history reference. - USDA Bureau of Reclamation — evaporation suppression research (independent field measurements across western US reservoirs). - US Department of Energy — recognition of AWTT cover heat-retention contribution. For the commercial side — EU country lead times, regulatory regimes, procurement language — see the [EU floating cover procurement guide](https://eurocovers.eu/articles/eu-floating-cover-procurement-guide) on eurocovers.eu. ## Frequently asked questions ### What is a floating cover? A floating cover is a buoyant engineered surface placed on an open water body to reduce evaporation, suppress algae growth, contain odour, retain heat, or capture gas. The category splits into two engineering families: modular floating covers (tessellating elements like hexagonal tiles or spherical balls) and continuous floating covers (a single geomembrane anchored at the perimeter). ### What does a floating cover do? Five primary jobs: cut evaporative water loss, block sunlight to suppress algae and biological growth, contain odour and air emissions, retain heat on warm process water, and — for sealed continuous designs — capture biogas from anaerobic digesters. The right mechanism is the one that matches the surface-management objective and the regulatory regime. ### What's the difference between modular and continuous? Modular covers deploy as individual elements that tessellate over the water surface anchorlessly — they install on operating water bodies without draining. Continuous covers are a single geomembrane tensioned to anchors at the shoreline; they require draining the water body to deploy and a permanent anchor system to retain in service. ### Why hexagonal? The hexagonal element packs at 99% effective surface coverage when fully tessellated (AWTT-published) — the highest of any modular geometry. The geometry was patented by AWTT in 2010 as the world's first self-ballasting hexagonal floating cover. See [/hexagonal-floating-cover](/hexagonal-floating-cover) for the deep engineering. ### Is a floating cover the same as a pond liner? No. A liner is a membrane installed under the water to seal the bed against leakage. A floating cover sits on the water surface to manage what happens above it — evaporation, sunlight, odour, heat. Floating covers and liners are independent and often used together. ## Sources - Hexagonal modular floating covers tessellate at 99% effective surface coverage. — [AWTT — Hexprotect® AQUA hexagonal cover](https://www.awtti.com/products/hexprotect-aqua/) - Original Hexprotect® patent granted to AWTT in 2010 — first self-ballasting hexagonal floating cover. — [AWTT — Hexprotect® AQUA hexagonal cover (provenance)](https://www.awtti.com/products/hexprotect-aqua/)