Foam densities, taper, locking straps, and the one accessory that doubles a cover's life. Practical buying advice for a UK garden setting.
A good cover is the cheapest energy-saving upgrade you can make. The wrong cover is the most expensive part you can ignore, because it costs you on the electric meter every single hour. Here is what genuinely matters when you are choosing.
Look for closed-cell foam at 2 lb per cubic foot density or higher. Anything lower compresses, sags, and pools rainwater within a year.
The taper from centre to edge should be 4 inches down to 3 inches at minimum. The slope sheds rain rather than pooling it. Flat covers are a false economy in the UK climate.
The vinyl skin should be marine-grade with UV inhibitors. The colour does not matter for performance but darker colours hide algae stains from leaf debris better.
Four locking straps minimum. They are required by your insurer, and they are also what stops a cover acting as a sail in a winter gale.
Storm straps that go over the top of the cover and clip to the decking are a good idea in exposed gardens. Replacing a cover that has blown off the deck and into the lawn with a snapped hinge is no fun.
Metal-reinforced lift handles outlast plastic ones by years. They cost a few pounds more on a new cover, less than a single replacement set.
A floating thermal blanket. Five to ten pounds, sits directly on the water under the main cover. It blocks the evaporation that soaks the foam from below, which is the actual reason most covers fail.
Pair it with a quarterly cover wipe with a vinyl protector. Five minutes of work, doubles the time before the skin cracks.
If you are buying new, a reputable supplier will quote a 5-year skin warranty and a 3-year foam warranty. Anything shorter says how much they trust the build.
Soft (foam-cored vinyl) for almost every domestic UK tub. Hard covers are heavier, more expensive, and only worth it for commercial settings or sloping installations.
Two-person lift test. If you cannot lift it cleanly without it sagging in the middle, the foam is waterlogged. It is costing you money every day.