Specifier guide
How Long Does a Floating Cover Really Last?
Every modular floating cover on the market claims twenty-five years. The number is easy to print and hard to earn: service life is set by how much polymer is in the part, what that polymer started as, and what was compounded into it. Here is how to tell a supported projection from an unsupported one — including ours.
Start here: every lifespan figure is a projection
No supplier of modular floating covers — AWTT included — has twenty-five completed years of field data on a product built to today’s exact specification. The category is not old enough. Anyone publishing a twenty-five year figure is projecting from material science and from whatever field record they actually hold.
That is legitimate, and it is how durable-goods engineering works. What matters is whether the projection rests on something. A supplier with twenty years of covers still floating and a documented material specification is projecting. A supplier three years old with an undisclosed material specification is guessing, and the two claims should not be read as equivalent just because the number printed on them is the same.
The four things that actually set service life
Material mass per square metre
UV photo-oxidation and oxidative embrittlement attack polyethylene from the exposed surface inward. Two covers in the same climate degrade at a similar surface rate — so the one with more wall to lose stays serviceable longer. A cover using a third of the polymer per square metre gives up roughly three times the fractional cross-section to the same depth of degradation.
What to ask: Ask for grams per square metre of covered surface, not grams per module. Module weights are not comparable unless the modules tile at the same density.
Virgin resin or recycled feedstock
Recycled polyethylene has already been through at least one melt history. It arrives with a partially consumed antioxidant package, carries contamination that nucleates degradation, and has a broader, less controlled molecular weight distribution — which lowers environmental stress crack resistance. ESCR matters on a floating cover because the part sits under sustained stress in constant water contact for its entire life.
What to ask: Ask whether the resin is virgin or post-consumer, and ask for the resin producer and grade.
The stabiliser package
Unstabilised HDPE left outdoors embrittles in a few seasons. Service life comes from what is compounded in: a UV screen, antioxidants that interrupt the oxidation chain, and carbon black, which is the most effective UV absorber available and shields the bulk polymer beneath the surface. A cover can be thick and still fail early if this package is thin or absent.
What to ask: Ask what UV and oxidation inhibitors are used and whether carbon black is included.
Operating environment
UV dose, water chemistry, temperature cycling, and mechanical loading all move the number. A cover in the Atacama sees several times the annual UV dose of one in northern Europe. A published lifespan without a stated basis environment is not a specification.
What to ask: Ask which climate and service conditions the figure assumes.
The comparison that is almost never made
Two hexagonal covers can photograph identically and differ by a factor of three in the amount of polymer they contain. Because module sizes differ, the only honest basis for comparison is mass per square metre of covered surface. AWTT publishes its figure so that anyone can put a competing product beside it on the same basis.
| Basis | Hexprotect® AQUA | What to request from any supplier |
|---|---|---|
| Polymer per module | 200 g (dry) | Dry part weight, excluding ballast water |
| Modules per m² | 28 | Needed to normalise different module sizes |
| Polymer per m² of cover | 5.6 kg/m² | The only comparable number |
| Feedstock | Virgin HDPE, top-tier US producers | Virgin or post-consumer; producer and grade |
| Stabilisation | UV and oxidation inhibitors, plus carbon black | Inhibitor package and carbon black loading |
Polymer per m² is the module dry weight multiplied by module density; it excludes ballast water, which adds mass but no UV resistance.
Our own basis, stated plainly
It would be inconsistent to publish this guide and then decline the same questions, so:
- Field record. AWTT was founded in 2004 and designed its first modular cover concepts in 2004–2005 and the first self-ballasting hexagonal floating cover in 2006. The earliest installations have been in continuous service for more than 20 years. 700+ installations across 25 countries, 20+ million square feet deployed.
- Material. Virgin HDPE from top-tier US resin producers, with UV and oxidation inhibitors and carbon black. No post-consumer content. 5.6 kg of polymer per m² on Hexprotect® AQUA.
- Independent corroboration. A 2017 U.S. Department of Energy Sustainability Award for the Savannah River Site deployment, and covers that have remained in service through four named hurricanes.
- What we do not claim. We do not claim 25 completed years of field observation. Our 25+ year figure is a design life projected from the material specification and supported by the record above. We say so rather than implying otherwise.
Material certifications, resin documentation, and test reports are available to qualified specifiers on request — see verification & documentation.
Service life — frequently asked questions
Direct answers on what determines how long a floating cover lasts, and how to check a supplier's claim.