Why fire hydrants become useless even though there is water in the reservoirs.

In the first two days of the Mountain Fire, Crestview water pressure became unusably low in hydrants near the fires—and inside many homes even outside the fire zone.  This is why that happened.

At the time of the lowest water pressures, Wednesday evening and early Thursday morning, there was still water in both Crestview reservoirs. However, the rate at which water was being drawn out through hundreds of hydrants and broken service lines caused the pressure to drop precipitously. One knowledgeable person estimated that Crestview’s wells can only fill each of the two reservoirs at 1,200 gpm and that the withdrawal rate early Thursday was as high as 20,000 gpm. The effect was similar to, but much worse than, turning on all your yard sprinkler zones simultaneously, which reduces the pressure to all zones.  In fact, to keep the pressure up is why we have multiple irrigation zones.  Similarly, in some homes, warm water will become suddenly hot when flushing a toilet causes a sudden increase in cold water use.

Fire departments expect pressures to drop a lot when they draw from many hydrants at the same time.  That is why they have tanker trucks that fill up remotely where the pressure and flow rate are adequate and haul water to the fire fighters.  This industrial-scale bucket brigade is often necessary to fight wildfires.

Deputy General Manager of Calleguas Municipal Water District, Ian Prichard, explained that to the press in this video.

Prichard and fire officials said there was no lack of water during the Mountain Fire and that they were able to deal with the low pressures.

Prichard also explained that these hillside water tanks are designed only to support a community’s daily use as well as a large structure fire — one that might take three or four firetrucks. None are designed for a major fire blowing embers every which way that requires hundreds of firetrucks, he said.

“Even with electricity … it puts a lot of stress on that system; you draw down that tank faster than it can get refilled,” Prichard said. “Firefighters know this, they’ve been fighting wildland-urban interface fires for a long time.”

However, he was adamant that in this fire “there was still water available and firefighters knew that and responded accordingly.”

Many fire officials echoed that defense.

“In the higher elevations, there was minimal water pressure due to how many [trucks] were tapped into the system,” said Capt. Scott Safechuck, a spokesperson for the Santa Barbara County Fire Department. “It’s part of the operations. …. We pivot to how we can get water.”

The Ventura County Star attributed to Ventura County Fire Chief Dustin Gardner its report that “the water system was being used to fill hundreds of engines. Every fire hydrant was being tapped.”

Apparently not understanding this, some shareholders are blaming low water pressure during the Mountain Fire on the fact that a permit to install Well #7 to back up Well #4 was denied in 2021 and that the effort to get permits for Well #8 to back up Well #6 was paused pending a search for a better location .  They speculate that the loss of Edison power to Crestview’s whole system Wednesday and the non-existence of Wells #7 and #8 caused the low hydrant pressure. As explained above, that is not how the system works. Eventually, failure to replenish the reservoirs would have been a big problem, but that did not happen during the Mountain Fire.

A portable generator was brought to Well #4, and it was pumping to the upper reservoir by about 1:00 a.m. on Thursday.  From about 2:00 p.m. Thursday, Calleguas water was flowing into both Crestview reservoirs and filling them as fast as possible after arrival of an emergency generator for the booster pump that moves water from the lower reservoir to the upper reservoir.  When Calleguas water is being received, as it is for a few months almost every year, all Crestview wells have to be shut down.  The pipes are too small to accept well water and Calleguas water simultaneously. Many shareholders are frustrated and/or angry about the long time it is taking to make decisions about a new well location, but that delay has nothing to do with the Mountain Fire disaster.

UPDATED 1/12/25:  Similar water supply problems arose early in the devastating Palisades and Eaton Fires that started in Los Angeles County in early January 2025, according to this Los Angeles Times article.

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