How we judge and rank

What follows is meant to be held against the pages it produced. A method nobody can check against its own output is an intention, not a method — so each rule below names the thing it forbids, not just the thing it prefers.

Start with what will not fit

Before price, before any published figure, a page asks whether the thing will physically work with the pool already in the garden and the supply already in the wall. It goes first because it is the question that fills return labels, and because it is the one question a photograph can never answer.

In practice it is a handful of millimetre figures. The hose diameter a pump is cut for, 32 or 38 mm, which meet at no point. The cartridge type a filter housing takes — I, II, IV, VI, S1 — where the number is a shape and not a size. The thread on a multiport valve, 1½ inch or 2 inch. The wall thickness a skimmer's cut-out assumes. The liner attachment a pool was built for, overlap or bead, which are not interchangeable. Where a maker publishes none of it, the page records that it was not published — which is itself a finding about the listing.

The single rule the rest obeys

Nothing numeric is printed here without its source alongside it. Not in a footnote, not implied by a logo — alongside, in the same table row or inside the same sentence.

The reason is practical, not pious. Attach a source to a figure and any reader can argue with it, trace it, or write in and correct it. A figure with no source can only be believed. When a manual and a shopping listing contradict each other, the manual is what appears. When neither publishes anything at all, the field stays empty and the page says it is empty — because the moment a plausible substitute has been typeset, nothing on the page distinguishes it from something that was actually measured.

A headline figure never travels alone

Next comes whatever the listing shouts, and it arrives carrying the thing the listing usually drops. A pump's flow rate with the head it was taken at, or with the fact that no head was stated. A heat pump's COP beside the air and water temperatures it was quoted for. A pool's stated volume beside the geometric volume of its own dimensions. A cover's micron count with the film it describes, or the note that no thickness appeared anywhere.

Where a maker prints the number and leaves out the condition, the leaving out is what gets recorded. That is not fussiness: on this shelf the condition is very often the whole difference between two products quoting the same figure.

Four questions about the third summer

• The part that goes first, and whether anyone sells it separately. Filter cartridges, spider gaskets, salt cell plates, pump seals, liner seams, robot tracks and brushes — every family has exactly one. The page names it and says whether a spare can be bought, because that one fact is what separates equipment with a service life from equipment with a component life.
• What the carton turns out to be missing. The hose a filter is cut for and ships without. The salt a chlorinator needs in the water before it makes anything. The bypass a solar collector expects. The second cartridge, so the first can dry. Anything demanding a further purchase before it works was never the price on the label, and the page puts the difference back.
• What the garden is expected to supply. Ground level to within two centimetres across the whole footprint. A socket at a stated distance with the protection the maker specifies. Somewhere for several hundred litres of backwash to go. A path wide enough for a crate that will not pass a side gate. These are published often enough to compare, and they rule products out rather than ranking them.
• Whether it can be bought where you are reading. Every reference is confirmed store by store before the page goes up, and each page lists the markets that had an offer. Excellent equipment nobody stocks in your country is not a recommendation, it is a frustration.

Which source loses when two of them disagree

For anything structural — hose diameters, cartridge types, thread sizes, wall thicknesses, bead profiles, what a spare states it fits — the manufacturer's own documentation is read first and the marketing headline last. The order flips for anything set in the largest type on the carton, for the obvious reason that the largest type is there to sell.

Ratings and markings come second, and they are handled as claims due for re-confirmation rather than as permanent properties of an object. A maker changes a gasket, an impeller or a supplied cartridge without touching the model name, and a standard gets revised on a timetable of its own.

Owners a year or two in come third, and for one question they have no substitute. No specification sheet records whether a salt cell still produces after two seasons, whether a spider gasket has hardened, whether a liner seam has opened, or whether anyone still answers the support address. Where a judgement rests mainly on one of these three, the page says which. Where none of the three answers, the page says so instead of reasoning its way to a number.

Copied out, never worked out

This shelf is sold on numbers, and a number is the easiest thing in any listing to repeat without thinking about it. One rule governs every page that carries one: every volume, flow rate, head, COP, hose diameter, film thickness in microns, grain size, active chlorine content, dose per cubic metre, salinity, runtime and quoted noise level on this site is copied from the manufacturer, in the unit it was published in, with its source named — and not one of them is recalculated, converted or deduced here. Where a maker publishes nothing, the page reports that nothing was published.

The COP is where that rule earns its keep. Dividing a heating output by an electrical input takes two seconds, and the ratio would look perfectly authoritative set in the same typeface as everything around it. It would also be our figure rather than the maker’s, measured at no stated temperature, and nothing in the typography would tell you which of the two you were reading.

A place in a family, not a mark out of ten

Nothing here carries a score. A single mark would have to set a heat pump against a tub of tablets, and no honest exchange rate exists between those two objects. What a page gives instead is a position inside one family, with the sentence that earned the position printed next to it.

Families run from the modest upward, not from the expensive downward. Almost everybody arrives with a budget already decided and one specific hole to fill; a page that opens on the dearest thing on the shelf is answering a question nobody came with.

What the commission pulls at, and what holds

Affiliate income leans towards whatever is expensive, newly launched and enjoyable to write about. What leans back is structure rather than good intentions: no family has been reordered for earnings, more than one page here ends by recommending a rake and an afternoon instead of a machine, and a position has never been exchangeable for anything at all.

One distortion belongs to this subject in particular, and naming it works better than quietly resisting it. Pool equipment is sold on capacities no private garden will ever reach. Build a page around those and it recommends the largest number in every family, because a larger number can always be argued for. Where the honest answer is that the upgrade changes nothing you would notice — a pump rated for 60 000 litres on a 10 000-litre pool, whose extra flow only drives water past the cartridge faster; a heater sized for a season nobody swims in; a robot sold on a runtime longer than the pool takes to clean — that is the answer the page gives.

One bias cannot be structured away. What this site covers is what can be bought through the Amazon stores of the United States, the United Kingdom, Germany, France, Italy and Spain. Equipment sold only direct, or only through pool trade suppliers, is under-represented here as a result, and wherever that shapes a conclusion the page says so.

What a published figure actually undertakes

All of the above rests on one distinction, and that distinction is why these pages sound less certain than the ones sitting beside them in a search result: a published figure records what a maker wrote down under conditions the maker chose; it does not undertake an outcome in your garden. Where a named standard stands behind it, the standard describes a test — a defined quantity, applied in a defined way, for a defined duration. Where none is named, which is most of this shelf, the figure is the maker’s own. Neither is a statement about a particular pool, a particular week of weather or a particular Saturday with eight people in the water. Treat either as a promise and you sell more equipment, at the price of misleading somebody about what they bought.

Two sentences you will not find on this site

Both limits are fixed, and both read better stated outright than left for a reader to infer. Nothing here — no cover, no ladder, no alarm, no chlorinator — is described as making anything safe. A page reports what the maker specifies for its own product: the load cited, what that load covers, the construction, the fixing, the inspection asked for and the replacement interval. The rest belongs to those instructions and to the local rules, because whether a pool is safe depends on how it was installed, what surrounds it and who can reach it — and no listing knows any of that.

And no page here says what your water needs. A dose per cubic metre is a property of a product. What a particular pool requires on a particular day depends on bathers, sunlight, rainfall and what is already dissolved in it — it is not printed on any box, is not ours to state, and is the one recommendation this site is structurally unable to make honestly.

Where the page ends and the manual begins

None of this substitutes for the manufacturer's instructions. For the electrical protection a pump outdoors requires, for the earthing of a heater, for the two chlorine products that must never meet, for the ground flatness a steel wall assumes and for the sequence a frame is assembled in, the page points at those documents — and at the safety data sheet — rather than rewording them, even though a page that stops there earns nothing.

A last limit gets repeated on every page it touches rather than stated once here and assumed thereafter: whether two things fit is settled by a figure or a list the maker published, and never by how they look next to each other. A hose diameter decides which pump meets which filter. A cartridge type decides which element drops into which housing. A bead profile decides which liner a pool will hold. A cell length decides which chlorinator fits which union. Where a maker publishes none of it, the page reports the answer as unpublished rather than deducing it from a photograph or a product name.