How Pages Are Checked
In short
Every figure on Chalk & Cistern traces to a named document, such as a regulation, an Approved Document, a regulator's guidance or a maker's manual, with the year it applies to.
Updated
Where figures come from
Each number on a page comes from a primary document that anyone can open: legislation.gov.uk for the regulations themselves, the Approved Documents published on gov.uk, the Drinking Water Inspectorate, the HSE, Ofwat, the Met Office, Water Regs UK, Gas Safe Register, and the user and installation manuals that boiler makers publish. Portsmouth Water's own web pages, leaflets and zone data are used for local figures.
The link sits on the claim it supports, so you can read the clause or table yourself. Where a page quotes wording, the words are copied from the source rather than paraphrased into something stronger. When two sources disagree, as makers do on boiler pressure, the page gives each figure with its owner instead of blending them into one rule.
Local numbers
Local figures carry their date because they change. Hardness comes from Portsmouth Water's 2026 zone table, issued in February 2026; chlorine and other measured values come from the company's 2025 zone summaries; frost figures are the Met Office's 1991–2020 averages. Pages say which year a number belongs to and when the source was read.
Portsmouth Water splits its area into supply zones, and a street's zone does not always follow town boundaries. So the pages give the range across the zones and send you to the company's own zone lookup for a specific address, rather than guessing which zone a postcode falls in.
What is left out
Some things are missing on purpose. There are no laboratory tests of anyone's tap water, no figures taken from forums or anonymous posts, and no prices for trade work such as call-outs, powerflushing or gas safety checks, because none could be sourced reliably. Claims that could not be confirmed on an opened page, including anything from Southern Water's website, which could not be read, are left out rather than repeated second-hand.
Where a US shop's listing appears, what it says about its own product is reported as the shop's claim, and health or purity promises that no certifier backs are not repeated at all.
Corrections
Regulations are amended, utilities update leaflets and makers revise manuals. When an error or an out-of-date figure is found, the page is corrected and the date in its byline moves forward. A correction replaces the wrong figure; it is not left standing beside the right one.