Water fire extinguishers are one of the most common types you'll see in workplaces, schools, and many commercial buildings across the UK. Despite the rise of high-tech foams and gases, water remains a staple of fire safety. But how exactly does a canister of H2O take down a fire, and when should you (or shouldn't you) use one?
At Barbon Fire Protection, we believe understanding your equipment is the first step to staying safe.
What Is a Water Fire Extinguisher?
A water fire extinguisher uses straight water or water with an additive as its extinguishing agent. These red cylinders are highly pressurised, using compressed nitrogen or air as a propellant to force the water out at high speed.
Water extinguishers work well on Class A fires, those involving solid, organic materials such as:
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Wood
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Paper and cardboard
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Textiles and carpets
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Plastics and rubber
Water additive fire extinguishers (like our FireShield Water Compact Plus Fire Extinguisher) do the same job, but with greater efficiency and penetration.
Additives make the water "wetter" by breaking down its surface tension.
Notice how rain forms droplets on a freshly waxed car or sits on fabric instead of soaking in right away. That's surface tension. It's what makes water bead up rather than spread out.
On a fire, that means plain water can sometimes run off the surface of burning materials instead of soaking in properly.
Plain Water vs. Additives
Additives, such as soaping agents, polymer gel, and antifreeze, increase the effectiveness of water. They make water soak deeper into the material and stick better to vertical surfaces.
Because the water works harder, you don't need as much of it. This allows for much lighter, more compact extinguishers.
A standard 9-litre water extinguisher is quite heavy to lift in an emergency. Additive models achieve the same (or better) fire ratings in much smaller packages.
|
Extinguisher Type |
Capacity |
Fire Rating |
Total Weight (Approx) |
|
Standard Water |
9 litre |
13A |
15kg |
|
Water Additive |
3 litre |
13A |
5.5kg |
|
Water Additive |
6 litre |
21A+ |
10kg |
As most UK premises require a minimum of a 13A rating per 200sqm of floor area, the 3-litre additive version is a game-changer for accessibility and ease of use.
How Water Fire Extinguishers Work
Fire only keeps going when three things are present: fuel, oxygen, and heat. Water fire extinguishers go straight after the heat.
Water sprayed onto a fire soaks into the burning material and absorbs the heat from it. As a result, the temperature of the fuel drops quickly. Once it cools down enough, it simply can't keep burning, and the fire dies out.
Plus, as the water hits the flames, some of it turns into steam. That steam expands and displaces some of the oxygen surrounding the fire. It's not the main reason the fire goes out, but it does give the extinguisher a small boost while the cooling does the real work.
When Not to Use a Water Fire Extinguisher
In the UK, fires are categorised by "Classes," based on what's burning. As mentioned earlier, water extinguishers are designed specifically for Class A fires.
Using water fire extinguishers on the wrong fire isn't just ineffective. It can be dangerous.
To stay safe and avoid making the situation worse, never use them on the following:
|
Fire Type |
Why Not? |
What Fire Extinguisher to Use Instead |
|
Electrical fires |
Water conducts electricity; risk of electrocution |
CO2 or dry powder (like the FireShield ABC Dry Powder) |
|
Class B (flammable liquids) |
Water can spread the liquid, spreading fire |
Foam, dry powder, or CO2 |
|
Class C (flammable gases) |
Water cannot put out a gas leak |
Dry powder (only after the gas supply is isolated) |
|
Class D (flammable metals) |
Water can react violently with some metals, causing explosions or toxic fumes |
Specialist dry powder (L2 or M28) |
|
Class F (cooking oils and fats) |
Water can cause hot oil to splash and flare up |
Wet chemical |
How to Use a Water Fire Extinguisher Correctly
Water fire extinguishers are simple to use, but panic can set in quickly. To stay calm, remember the PASS acronym:
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Pull the safety pin to break the tamper seal.
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Aim the nozzle at the base of the fire, not the flames.
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Squeeze the lever to start the flow.
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Sweep the jet side-to-side.
Continue to aim low, at the fuel source, and keep going until the fire is fully out.
Maintenance of Water Fire Extinguishers
Here's your maintenance checklist:
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Perform monthly checks. Ensure the pressure gauge is in the green and the pin is in place.
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Have your fire extinguisher serviced annually to check the components for damage.
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Test-discharge and refill your fire extinguisher every five years.
Final Thoughts
Water fire extinguishers work by cooling fires until they cannot burn anymore. That's why the familiar 9-litre red cylinder has been part of UK fire safety for so long.
Today's water additive models offer better fire-fighting power. They're lighter, more efficient, and much easier for the average person to handle in an emergency.
Need advice on your fire safety setup? Our team can help you choose the right extinguishers for your building, so give us a call and let's get it sorted.
