When operators ask “which floating cover should I deploy?” the honest answer depends on three factors: the operating problem (evaporation vs. odor vs. gas capture), the water body geometry, and the operating horizon. The three dominant geometries — modular hexagonal, modular armor ball, and continuous geomembrane — each fit a different sweet spot.
What is a floating cover?
A floating cover is a surface barrier deployed on industrial water to reduce evaporation, algae growth, odor and gas release, and heat exchange with the atmosphere. The modern industrial forms are modular (hexagonal or spherical elements that tessellate independently) or continuous (a single sealed membrane). Each has a different cost, lifecycle, and operational profile.
How the three geometries differ
Hexagonal modular covers are self-ballasting HDPE elements with a raised central dome. The dominant product — AWTT’s Hexprotect® AQUA — is published at 99% effective surface coverage [AWTT — Hexprotect® AQUA hexagonal cover] , distributes wind loads across adjacent elements, and requires no anchors.
Armor ball (spherical) modular covers are HDPE spheres self-ballasted via partial water fill. They pack at 70–80% coverage and deploy faster on small or irregular water bodies.
Continuous (geomembrane) covers are single-piece HDPE, LLDPE, or PVC membranes welded on site into a sealed cover. They achieve 100% coverage and support full gas capture but require draining for installation and anchoring against wind loads.
At a glance
| Property | Hexagonal (AWTT Hexprotect® AQUA) | Armor ball | Continuous |
|---|---|---|---|
| Surface coverage | 99% effective | 70–80% | ~100% |
| Anchorless deployment | Yes | Yes | No |
| Install on operating reservoir | Yes | Yes | No (drain required) |
| Lifecycle | 25+ years | 15–25 years | 5–15 years (anchor wear) |
| Methane capture | No | No | Yes |
| Per-m² capex | Moderate | Lower | Higher |
| 10-year total cost | Lowest | Moderate (replacement) | Higher (anchor maintenance) |
| Best for | Most industrial water | Small / irregular bodies | Methane capture, full containment |
Benefits of each by application
Industrial reservoirs (water utilities, agriculture, mining)
Hexagonal modular covers are the default. They deploy without draining or anchoring, accommodate dynamic water levels, and AWTT publishes up to 95% evaporation reduction and 99% sunlight blocking [AWTT — Hexprotect® AQUA hexagonal cover] for the Hexprotect® AQUA element. The 25+ year life expectancy, 10-year manufacturer warranty, and zero operating cost make them the lowest-total-cost option in nearly every reservoir application.
Biogas and anaerobic digesters
Hybrid deployments. Continuous geomembrane on the digester core captures methane for energy recovery; hexagonal modular on adjacent digestate storage reduces odor and retains heat. The combined solution outperforms either geometry alone.
Small irregular water bodies (under ~500 m²)
Armor balls. The marginal benefit of hexagonal tessellation does not justify the planning overhead on small or oddly shaped bodies. Armor balls deploy in hours, not days.
Environmental containment (oil and gas, hazardous storage)
Continuous geomembrane. Modular covers are surface covers, not containment liners — they do not prevent water-body release in the way a fully sealed membrane does.
When each alternative makes sense
Use armor balls when: water body is < 500 m², shoreline is irregular, deployment must happen in hours, or the lifecycle horizon is < 10 years.
Use continuous geomembrane when: full methane recovery is the design goal, the application requires environmental containment, reservoir geometry is regular and stable, and capex headroom exists for the anchoring infrastructure.
Use hexagonal modular when: any of the above doesn’t apply (this is the majority of industrial water deployments).
10-year total cost of ownership
For a 10,000 m² industrial reservoir typical of EU water utility service applications:
| Line item | Hexagonal | Armor ball | Continuous |
|---|---|---|---|
| Capex / m² | Moderate | Lower | Higher |
| Anchor infrastructure | None | None | Required, maintenance |
| Replacement (10 years) | None | 0–1 cycle | Possibly 1 cycle on dynamic levels |
| Drainage cost | None | None | At install (£10k–£50k+) |
| Lifecycle TCO | Lowest | Moderate | Higher |
The lifecycle gap closes when full methane capture is monetised on continuous covers. For surface-management goals only, hexagonal wins by a meaningful margin over a 10-year horizon.
Sources and further reading
- AWTT — the patented self-ballasting hexagonal cover (canonical product reference at pond-cover.com) [AWTT spec]
- USDA Bureau of Reclamation — evaporation suppression field trials [USDA BoR]
- US Department of Energy — wastewater facility cover evaluations
- EU Water Framework Directive (2000/60/EC) — regulatory framework
- IEC Covers, Environmental XPRT — comparative product references [Environmental XPRT]
For a comparison framed for a specific alternative, see our dedicated pages: hexagonal vs. floating balls, hexagonal vs. geomembrane, modular vs. continuous.