OL postcode district map, Oldham

Where the OL districts sit

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

Where OL sits

It is administratively fragmented, reaching into Oldham, Rochdale, Lancashire and Tameside and 1 other authority.

Water supply across OL

All 16 OL districts are supplied by United Utilities. That makes OL simple in a way many areas are not: one company, one set of rules, one status to check.

No hosepipe ban currently applies anywhere in OL.

The shape of the OL area

OL12 is the largest district with 1,185 postcodes around Whitworth, and OL5 the smallest with 370. The area divides into 68 postcode sectors.

Several districts share a settlement, which is a common source of confusion when a form rejects an address: OL1 and OL8 all point at Oldham, OL3 and OL4 all point at Lees and OL6 and OL7 all point at Ashton-under-Lyne.

What borders OL

OL sits next to HX (Halifax) to the north east, BL (Bolton) to the west, M (Manchester) to the south west, HD (Huddersfield) to the east and SK (Stockport) to the south.

Its neighbours run in 5 different directions, so OL is landlocked by other postcode areas on most sides.

OL 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 OL

Figures are in milligrams per litre as calcium carbonate, the unit UK water companies report in. 1 of 16 districts has a published figure.

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.

Descriptions such as very soft, soft, moderately hard, hard, very hard are the water industry scale: very soft below 75, soft 75–125, moderately hard 125–250, hard 250–375, very hard above 375 mg/l. Your supplier may use a different scale for the same number.

Contains Yorkshire Water drinking water quality data, via Stream, licensed under CC BY 4.0. Edition 2026, published 1 January 2026. Yorkshire Water publishes this as mg/l without naming the species. We read it as calcium carbonate because the determinand is Hardness total and the dataset contains no calcium determinand. Evidence: determinand "Hardness total"; DWI code "HARD T"; no calcium determinand published in the dataset.

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 OL 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