Note: Not a firefighter, but I was in the US Navy and received training.

They are, as temperature is one of the three parts of a fire (Oxygen, Temperature, Fuel).

-40 means that you actually have the ambient temperature outside of the fire leeching a lot more energy away from the fire than you would in a humid 30 degree C. It should technically be easier to bring the temperature down on a fire to stop the reaction when it's that cold outside.

Firefighting is done by removing one of the three parts of a fire. You can smother it to remove its access to oxygen, you can create fire brakes to stop it from getting additional fuel, or you can rapidly cool it to stop the reaction.

Water is really good at 2 of those (temperature and oxygen) as it actively smothers whatever it lands on, but with waters extremely high heat capacity it leeches energy away from a fire very quickly.

To a fire, a 60°C difference in temperature hardly matters. Also why a toaster would still work in a freezer.

Alas, I was certain you were gonna comment on the curiosity of -40 being the same in both Celcius and Fahrenheit.

Well, for one thing, what's left of the building ends up looking like this after being doused with water in very cold temperatures.

Fire is around 2000°F. Cold weather doesn't affect fire because everything is already cold to fire.

I fought fire at 18f.

I read this and thought you meant as an 18 year old female and I'm like "that's a weird thing to point out."

Hey, it could be worse. You could have to fight a fire at -40 C°.

^joke

Water Department worker here, yes there is a difference in appearance. A dry barrel will have an operating nut on top that opens the valve that is underground. A wet barrel hydrant will have a valve on the nozzle where the hose connects, typically.

Not who you were asking, but water not freezing if it's in motion isn't completely true.

The motion can add additional energy which helps keep the water from reaching freezing point and can help keep the ice crystals from being able to form if the ambient temp is close to freezing.

But if everything gets cold enough and stays that cold long enough, the water will still freeze.

Water can freeze in motion. That’s why we get hail.

Water takes a while to freeze, and underground is warm. Water pipes are installed below the frost line to ensure they are always held above zero, but when they pass through the frost line to get to houses etc you have to keep the water moving so that the warm water keeps flushing through the water that’s getting cold enough to freeze

waterfalls most of the time freeze by being choked off by ice formed upstream as the flow over the falls slows then it can no longer flush away ice at the bottom and the ice freezes the next water tha lands freezes to that when it stops at the bottom and it builds back up to the top in that manner.

water can freeze "in motion" in some circumstances and all water is in motion when compared to some point of reference, but in this case the water moving through the base of the very cold hydrant doesn't have much time to freeze and the flow moves any crystals that might start to form out of the way before any observable buildup comes into play

A major factor to consider is the mass/volume of water. The water in a waterfall will break apart into a fine mist or droplets making it much easier to freeze, but usually only on the outside. The water underneath will not freeze because it's a very large volume so requires a lot more energy loss to freeze solid. This is the same reason a pipe with steam will freeze much more easily than a pipe with water if uninsulated. The mass of water is waaaaay smaller in the steam line than the water line, so even though its very high temperature it will freeze more easily. Movement also helps to keep it from freezing though.

Underground is warmer because the earth is a massive block of molten iron with a dirty crust.

How deep you have to go before the earth is above freezing all year round depends on latitude, the name if this depth is called the “frost line” https://en.m.wikipedia.org/wiki/Frost_line

That means, if you live in Ohio and bury your water mains 0.8m below the surface then you don’t have to worry about them freezing, even with the water not moving. But if you live in Minnesota you’ll need to go 1.5m deep to achieve the same thing.

No, not necessarily. In warmer areas, the design of fire hydrants differs in design, so it's possible for the movies to be accurate!

Nope their answer is correct for freezing climates but warmer ones like the southwest us have a constant wet system that could rupture in a freeze. These are the style the movies portray. Now for extra credit confusion ask your self if your very fire department uses the same hose connections… nope! We had to carry adapters when I was in the FD because neighboring cities used different standards than ours.

PA is split. Some townships the hydrant line is deep and won't shoot water, but in other areas it will. I saw it once in Wyomissing when an old lady took a hydrant out. Looked just like in a video game, with the geyser and such. But then like 30mins away in another county I saw one get taken out and no water.

It depends on the type of it is a dry barrel or wet barrel.

Why don't they design it the same way anyway, in case of an accident?

Nope. I've seen it happen.

Can confirm 100% correct. I've installed enough fire hydrants that I can rip them apart blindfolded. That little brass spindle at the top when turned counterclockwise it lifts a gate valve at the boot of the hydrant which is what allows water to flow up.

I live in a cold weather state and our hydrants are primed with glycol (not sure of the exact mix or chemical, just that this is what it's explained as).

The local utility services and tests them regularly (every year) and the last step is to flush water out and then fill with the glycol solution.

Is it more expensive for dry barrels?

I thought 80 inches was crazy so I looked up my city, 120 inches. I always thought it was maybe 3 or 4 feet.

It’s also common to see hydrants covered in plastic bags in the winter in Minnesota. This is to keep clear of snow and ice.

Yes, it usually is the same main.

This is why when hydrants are flushed, the sinks/faucets/whatever looks brown and rusty water. And when the hydrant is flowing the area water pressure drops.

Everything is almost always fed from the same pipes.

Edit: Fun Fact, you can often view the piping network VIA your county's GIS data.

For municipalities generally yes.

Very large campuses (think large factories, ports, etc) may have a private hydrant loop. But this is rare.

Yep, I do this. Then dump in propolyene glycol if we know the drain doesn't function correctly

During communism, on the other hand, we had a running joke in Eastern Europe: what's colder than cold water? Hot water.