Can You Put Out a Fire with Seawater? Does it Work?

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With the wildfire crisis becoming increasingly dangerous, resourcefulness has become crucial. Freshwater is a renewable resource but can become scarce in times of disaster. Using saltwater from the sea or ocean seems like an easy enough solution, so why aren’t firefighters using seawater to put out fires?

Fire can be put out with seawater, though it is not usually used to do so. Saltwater can effectively extinguish fire, but it may damage firefighting equipment and hurt plant life if used.

Saltwater use creates problems for both the water distributing equipment and the surrounding environment. Read on to get the details about how the extinguishing process works and why seawater is not usually the best tool for fighting fires. 

Also read: How Long Does A Fire Investigation Take?

How Do We Extinguish Fires?

There are a few different methods for extinguishing fires. Water puts out fire by cooling (reducing heat) and smothering (cutting off oxygen). So, there’s not any reason why saltwater wouldn’t work as effectively. 

To learn more about the fire triangle, the science of how water puts out fire, as well as the other extinguishing agents that firefighters use, read: What Do Firefighters Use to Put Out a Fire?

A popular myth involving saltwater and fire states that it could cause combustion when combined. However,  according to Daniel Tam-Claiborne’s article “Burning Salt Water on YouTube, Inventor Waits for Prime Time” from Popular Mechanics, it isn’t something that you should be concerned about. 

Fire Fighting Procedure

To understand where our problems using seawater come from, you have to know the basics of how you fight fire with water. 

Firefighters get water for extinguishing fires from two places: tanks inside of the fire engines and external sources like fire hydrants. The tanks on fire engines are filled with water from our underground water system. Fire hydrants, and just about every other external water source, provide water from the same underground water system. 

A vast majority of the standard fire engine is made of metal, including some water tanks. Hoses are not made of metal, of course, but the hose connectors (couplings) are. (Some newer types of fire hose have couplings that are made from materials that will not rust as easy or at all). These metal pieces are regularly cleaned and lined to keep rusting to a minimum. 

The water that we get from these sources is freshwater that flows through our underground water system. As Zhai Yun Tan explains in “How Do We Get Our Drinking Water In The U.S.?the water that we get from that system comes from lakes, rivers, and groundwater. 

Why Isn’t Sea Water Used?

helicopter dropping water on smoky wildfire

While we could be using saltwater to extinguish fires, there are a few problems that could arise. 

  • Corrosion — The first problem that arises with metal is corrosion, which is well-explained in the article, “Is Saltwater Affecting Your Pipes?” Corrosion of one of these water tanks or a hose connector could become dangerous and costly. (Rust is a type of corrosion)
    • Types: In “Find Out Why Naval Brass Is Capable of Resisting Corrosion Caused by Salt” from Rotax Metals, they discuss the two different forms of corrosion
      • Electron corrosion (or electrochemical corrosion) happens when salt ions break down the chemical structure of the metal. The addition of these salt ions attracts the metal’s electrons. This pulls them away from the structure of the metal, making it weaker. 
      • Anaerobic corrosion could also happen.  Here, sulfate deposits build up on the metal, which eventually corrodes the surface because of excess hydrogen. This is especially true if the salt water is in contact with the metal equipment for an extended period.

  • Environmental Effects — According to the academic paper, “Basics of Salinity and Sodicity Effects on Soil Physical Properties,” saltwater can harm plant life as well. If there is any chance of the water used for extinguishing fires to reach the soil, plants, or other vegetation, saltwater is not a good idea.
    • How? If you’ve ever heard the phrase “salt the earth,” you may already have a basic understanding of this concept. A simple explanation of this is that the salt hinders the uptake of water to the plants via osmosis. Salt in the soil makes water less available, essentially drying out the land and any remaining plants with it. 

Salt damage can make a piece of previously lush land completely barren for years to come. It would affect the entire ecosystem of the area, which is especially bad for places with lots of wildlife. This is even worse for environments that are specifically tailored to the needs of individual species. 

Some cases would be perfect for using saltwater to put out a fire. Beach fires on the sand are perfectly fine to use seawater on, as this would not harm any plant life. Saltwater would also be fine to use on buildings or in areas covered by concrete or tar, like cities. There are still other reasons why we don’t use saltwater in these cases, though. 

The tanks used to carry the water in fire engines can be made of metal, as well as many of the internal parts of the water pump, and saltwater corrosion would be a huge problem there. The amount of time that it takes to bring the water from the source to the fire would only exasperate this. 

Gathering salt water for the initial tank filling would also be much more complicated than it already is. The travel distance to and from the coast to collect water wouldn’t be nearly as efficient as using water from underground through a fire hydrant. 

Are There Times When Saltwater Should Be Used?

If we were to imagine a world where we used saltwater to fight fires, we would see a much less efficient picture of firefighting than what we have today. We have built our system and society in a way that makes the use of saltwater in firefighting just much too challenging and time-consuming. 

Coastal cities are the only places where using saltwater for fire fighting would make sense. They are near the water, where a firehouse could be placed close enough to pump the water directly in (using corrosion-resistant pumps, of course). 

Here is an example of a time when seawater was used for firefighting:

Crews attack California wildfires with ocean water

To minimize wildlife damage in any areas of growth, they could first distill the water. As described in the article “Desalination” from the United States Geological Society, this process would include boiling seawater and catching the steam. The condensation would have to build into another reservoir of freshwater. 

As you can see, this would be a much more complicated process than what we already do. So, while it is possible to use salt water, it is just significantly more difficult to do so. We can use seawater in a pinch if freshwater isn’t available, but we have to be aware of the effects that it might have. 

Conclusion

So, is it possible to use seawater to put out fires? Absolutely. It’s safe to use salt water to put out a fire on the beach or in your house. However, it isn’t the most effective kind of water to fight fires with. It’s not as easily accessible as freshwater, which is readily available to use via our underground water system. 

It is much more harmful to plant life. By soaking soil in salt water, you’re essentially starving surrounding plants of the soil’s water content, which, in turn, makes it a less inhabitable environment for any animals who live either entirely or partially off of those plants. 

Finally, saltwater corrodes the almost entirely metal-made fire fighting equipment that we use. That corrosion will lead to damage, constant repair, and could end up being the reason why fire isn’t extinguished fast enough. Using salt water to fight fires just isn’t worth all of the extra work that it would take. 

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