CH postcode district map, Chester

Where the CH districts sit

14 districts are plotted without a label where labels would overlap; every one is in the table below.

Where CH sits

It is administratively fragmented, reaching into Wirral, Cheshire West and Chester, Flintshire and Denbighshire and 0 other authorities.

CH spans the border: 14,751 of its postcodes are in England and 4,339 in Wales, about 23 per cent. That matters here in a way it does not on a plain postcode map, because water is regulated separately either side of it. In England the Environment Agency oversees drought and abstraction; in Wales it is Natural Resources Wales, and restrictions are set by whichever company supplies the address, not by which country it sits in.

Water supply across CH

All 38 CH districts are supplied by United Utilities, which is notable at this size: an area with this many districts usually crosses at least one supply boundary, and this one does not.

No hosepipe ban currently applies anywhere in CH.

The shape of the CH area

The districts are wildly uneven: CH7 holds 1,586 postcodes around Bwcle and CH90 holds 1, a ratio of about 1586 to one. They divide into 212 sectors.

The numbering is not continuous. CH runs up to 99 but has only 38 districts, so 61 numbers are unused:.

Several districts share a settlement, which is a common source of confusion when a form rejects an address: CH1, CH2, CH3, CH4, CH70, CH88 and CH99 all point at Chester, CH25, CH26, CH41, CH42 and CH43 all point at Birkenhead and CH27, CH28, CH44, CH45 and CH46 all point at Wallasey.

CH90 is a non-geographic district: it carries no coordinates because it is used for PO boxes and large users rather than for streets. It appears in the table below but cannot be placed on the map.

What borders CH

CH sits next to L (Liverpool) to the north, WA (Warrington) to the east, WN (Wigan) to the north east, CW (Crewe) to the south east and M (Manchester) to the east.

Its neighbours run in 4 different directions, so CH is landlocked by other postcode areas on most sides.

CH districts, settlements and water supply

Principal settlement is the town or city each district sits in or nearest to, derived from OS Open Names. It is not the Royal Mail post town, which is licensed data and not published openly. Status is resolved live from each company’s own notice.

Water hardness in CH

No water company covering CH publishes hardness figures as open data. The gap is named per district below so you know who to ask.

United Utilities does not publish hardness as open data, but does publish a water hardness factsheet with a full band table and a postcode water quality checker.

Hardness is published per census area, not per postcode, so these figures characterise a district rather than measuring one address. They are a scale and taste matter, not a safety one. Hardness data version wessex-water@2022-2025+yorkshire-water@2026.

Download the CH data

No signup, no email wall. GeoJSON carries the district points, the supplier and the live status, so it can be dropped straight into a map.

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District positions are averaged postcode centroids from OS Code-Point Open. They show roughly where a district sits, not where its boundary runs, and are not legal boundaries.

Frequently asked questions