> For the complete documentation index, see [llms.txt](https://docs.os.uk/os-downloads/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.os.uk/os-downloads/resources/product-resources/end-of-life-product-documentation/os-mastermap-water-network-layer/os-mastermap-water-network-layer-known-data-issues.md).

# OS MasterMap Water Network Layer Known Data Issues

This page provides the details of known data issues present in the final release of the OS MasterMap Water Network Layer product.

{% hint style="warning" %}

#### Product has reached its End of Life (withdrawal) date

The OS MasterMap Water Network Layer product (also referred to as OS MasterMap Networks – Water Layer) reached its End of Life on **31 March 2026**. As of this date, Ordnance Survey ceased to maintain or publish updates to the product, and access to the product was removed from the OS Data Hub, OS Features API and OS Vector Tile API.

Supporting product documentation will be removed from this site 12 months after this date, when access to existing data packages in the OS Data Hub is no longer available. Full details, including migration information and FAQs, are available on the [OS MasterMap Water Network Layer End of Life information page](/os-downloads/resources/product-resources/end-of-life-product-documentation/os-mastermap-water-network-layer/os-mastermap-water-network-layer-end-of-life-information.md).
{% endhint %}

## Known data issues <a href="#live-known-data-issues" id="live-known-data-issues"></a>

| Data Issue Name   | Data Issue Description                                                                                          |
| ----------------- | --------------------------------------------------------------------------------------------------------------- |
| Single Link Loops | 48 instances of single-link loops in the water network where the first and last vertex for a link are the same. |


---

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