Standards
What the markings actually record
Almost everything on this shelf carries a figure, and almost every figure gets read as a promise. None of them is. A flow rate records what a pump moved on a bench with nothing attached; a cartridge type fixes a shape and nothing else; a micron count describes a film, not a season of warmth; a COP records a ratio at one stated pair of temperatures. Each is exact, each is real, and not one of them says what will happen in your own garden. Some are published documents; several of the things this trade calls standards are conventions with no publisher at all, and the difference shows up the day something will not fit. Each page says which it is, in four parts — what the document or the convention fixes, what it does not promise, what it works alongside, and which families on this site depend on it.
Water balance figures
What pH, total alkalinity, hardness and cyanuric acid are, the units each is published in, and which of them makes the others readable.
- Stated pool volume — a figure quoted at 90 % of wall height Market convention
- Available chlorine — the percentage that makes two chemistries comparable Water-balance figure
- Dose per cubic metre — a statement about a product, not about your water Water-balance figure
- Cyanuric acid — the figure that accumulates and never leaves Water-balance figure
- Pool salt purity — 99.9 % NaCl, and what the last tenth is Water-balance figure
Hose and thread standards
The two hose diameters, the 1½" and 2" threads, the 1¼" and 1½" pole clips, and the designations German listings use for each.
Material and thickness
Microns, deniers, millimetres of liner and grams per square metre — the material figures that predict behaviour, and how rarely they are published together.
Equipment test standards
The European standards that do apply to pool equipment and to electrical safety around water, what they test, and which classes exist.
Market conventions
Volume stated at 90 % of wall height, COP quoted at 26 °C, flow measured at zero head: widely used, universally understood, and standardised by nobody.