When we think of firefighting, one of the first images that comes to mind is a fire crew connecting a hose to a fire hydrant. But in the UK, fire hydrants are often underground—and not all are the responsibility of the water company or fire service.
So what exactly is a fire hydrant, and how do public and private hydrants differ? If you’re a building owner, landlord, or facilities manager, understanding the difference could be essential to your legal fire safety duties.
What Is a Fire Hydrant?
A fire hydrant is a water access point connected to the public or private water supply network. It allows the fire and rescue service to access a high-volume water supply for firefighting. Hydrants are usually located underground and marked by a yellow “H” plate at street level.
There are two main types:
- Public fire hydrants – maintained by the local water authority and available to fire crews on public roads and footpaths.
- Private fire hydrants – located on private land or within commercial premises and are the responsibility of the landowner or managing agent.
Both types must be clearly marked, accessible, and regularly maintained to ensure functionality in an emergency.
Understanding Fire Hydrant “H” Marker Posts
The most visible indicator of a fire hydrant is the yellow “H” sign or marker plate. These are found mounted on posts, walls, or fences close to the hydrant and give essential information to fire crews. Understanding what these markers mean can help you identify where the hydrant is—and whether you may be responsible for it.
The standard fire hydrant sign has:
- A large black H in the centre
- Two black numbers—one above and one below the H
Here’s what they mean:
- Top number: The diameter of the water main in millimetres (e.g. 100 = 100mm)
- Bottom number: The distance in metres from the sign to the actual hydrant (e.g. 10 = 10 metres away)
Sometimes, additional small arrows indicate the direction you need to go to find the hydrant—left, right, or straight ahead. So if you see an H sign that says 100 over 10, the hydrant is 10 metres from the sign, and it’s connected to a 100mm water main.
It’s good practice to include this location information in your fire safety documentation, especially if the nearest hydrant is not directly outside your premises.
Public Fire Hydrants
Public fire hydrants are most commonly found on:
- Roadsides
- Pavements
- Outside residential developments or industrial estates
They are installed and maintained by the local water authority, and their locations are logged by the local fire and rescue service.
Key points:
- Fire services rely on these hydrants as part of their water supply strategy when attending fires.
- A yellow plate marked with a black “H” indicates the location and size of the water main.
- Maintenance involves periodic flow and pressure testing, access checks, and flushing.
Although the public is not responsible for these hydrants, you must not obstruct or build over them, and the fire service must be able to access them at all times.
Private Fire Hydrants
Private fire hydrants are installed within private property boundaries, such as:
- Business parks
- Shopping centres
- Industrial units
- Housing developments with restricted access
- Gated communities or private estates
- Warehouses, factories, and airports
These hydrants are usually required where:
- The nearest public hydrant is too far away to meet response needs
- The site is large or complex, making water delivery to remote areas challenging
- Firefighting vehicles may not have easy access during an emergency
The responsibility for inspection, testing, and maintenance of private hydrants falls to the landowner or “responsible person” under the Regulatory Reform (Fire Safety) Order 2005.
What Are the Legal and Regulatory Standards?
The installation and maintenance of fire hydrants in the UK must meet several standards and regulations:
- BS 9990:2015 – Non-automatic fire-fighting systems in buildings
- Water Industry Act 1991 – Sets out the responsibilities of water companies and governs the use of public water supplies.
- Building Regulations (Approved Document B) – Requires sufficient firefighting water access for certain building types and locations.
- Local fire authority guidance – Many local brigades issue specific requirements for hydrant locations and access.
Maintenance Requirements for Private Hydrants
If you have a private fire hydrant on your premises or estate, you must:
- Inspect visually every 6 months
- Conduct annual flow and pressure testing
- Flush out the system as needed
- Keep access clear and visible
- Maintain signage and identification plates
All testing should be completed by a competent contractor, and records kept for fire safety audits and insurance compliance.
How to Find the Nearest Fire Hydrant
Knowing the location of your nearest fire hydrant is an important part of fire safety planning—especially when completing a fire risk assessment.
A helpful online tool is the RISCAuthority Hydrant Map, which shows the location of publicly recorded fire hydrants across the UK. It can be accessed here:
👉 RISCAuthority Fire Hydrant Map
Using this tool, you can:
- Identify how far the nearest hydrant is from your business premises
- Assess whether additional private hydrants may be required
- Prepare better evacuation and firefighting strategies
- Share vital information with your fire risk assessor or insurance provider
How ESI Can Help
At ESI: Electrical Safety Inspections, we work with managing agents, landlords, and facilities teams across Farnborough, Camberley, Reading, Guildford, and the surrounding areas to keep private fire hydrants compliant and operational.
We can:
- Carry out scheduled inspections and flow testing in line with BS 9990
- Provide condition reports and identify any required remedial work
- Advise on signage, accessibility, and long-term maintenance plans
- Support your wider fire safety obligations, including fire risk assessments and system testing
If you’re unsure whether a hydrant on your site is public or private—or when it was last tested—get in touch with our team. We’ll help you stay compliant and ready to respond in an emergency.
