The majority of roughly 600 calls that the Denver Fire Department answered on Monday, the coldest day of the polar vortex that covered the metro area over the weekend, involved burst water pipes.

And though temperatures picked back up into the mid-to-high 30s on Tuesday, the city received 780 more calls, most of which dealt with flooding and water pipes, according to the Denver Department of Public Safety.

The department received an average of 345 calls a day during 2023, less than half of emergency officers received on Tuesday.

Though frigid temperatures freezing pipes is often the scare during artic blasts, officials said the thawing period can raise more problems for emergency responders, homeowners and plumbers alike.

Dustin Hafen, general manager and master plumber at Aurora Plumbing Company, estimated that work capacity has gone up 35% to 50% since the freeze.

“It’s been a while since we’ve had a deep freeze like this,” he said, thinking back on his 27 years as a plumber in the metro Denver area. “We saw a lot of broken pipes. We are still dealing with leftover, frozen pipes that have not thawed, which is crazy because of the warmer temperatures we’ve been seeing with the last few days.”

An investigation by The Building Research Council at the University of Illinois in 1996 found that the “temperature alert threshold” is 20 degrees, especially when pipes are uninsulated. The subzero temperatures can cause water within the pipes to freeze, expanding and breaking — or cracking — the pipes. 

Denver temperatures were below freezing for 93 consecutive and 33.5 hours below zero during the polar vortex from Jan. 12 to Tuesday. Some areas saw temperatures drop as low as -19, according to the National Weather Service Boulder.

Newer homes have moved away from copper and galvanized steel, opting for plastics and PEX pipe, according to Hafen. While these newer pipes allow for more malleable expansion, lowering the chance of busting, it makes thawing them safely more difficult.

“When a pipe freezes and it expands, you have to thaw the entire pipe,” Hafen said. While plumbers can use a pipe thawing machine on conductive materials, like copper, they have to rely on natural thawing for plastic pipes, making the process take longer.

“Water is a very destructive material,” he said. “It finds the path of least resistance. When it is unleashed, it tears things apart, and there’s repercussions for all courses of it.”

Along with freezing water, freezing soil can also cause issues, according to a spokesperson from Denver Water.

“Very cold temperatures cause water molecules in the soil to expand. The longer the cold spell, the deeper the frost layer can extend,” they said. “That frozen soil puts pressure on top of the pipes and can cause cracks.”

But the days of thawing, such as Tuesday, can cause just as much issue.

“By the same token, rapidly thawing ground after such cold stretches can also create breaks. As the soil warms, the ground can shift, also leading to pipe damage,” the spokesperson said.

Capt. J.D. Chism of the Denver Fire Department said that thawing can bring up problems homeowners were unaware of. They may not have noticed that the pipes were damaged until the thaw occurred, allowing the water to move through and expose issues.

Unaware moments like that may have lead to the drastic increase in water-line-breakage calls the department and plumbers received following the brutal cold.

“Come Wednesday afternoon, our phones were blowing up with floods. The homes had warmed up enough that the pipes dethawed,” Hafen said, noting that technicians at the company have added extra appointment times, stretching 8-hour work days to 12-14.

Denver Water said older pipes may have caused the increase in breakage, too: “Older pipes can be more vulnerable simply because they’ve been exposed to more freeze-thaw cycles over time.” 

The spokesperson noted that maintaining and replacing the 3,000 miles of pipes in the city’s system is a “big job.” When the department replaces pipes, though, technicians add a sand-gravel mix around the pipes to provide a cushion when the ground shifts.

In October, department officials revealed they are investing $1.9 billion into the city’s water system in the next 10 years, including the replacement of around 80,000 feet of water mains annually. 

These new improvements have led to the increase in monthly water bills for Denver Water customers. The estimated rate increase for a single-family home that uses the same amount of water as it did in 2023 will be an average of $1.60 to $2.30 extra per month, depending on where they live in the city.

Why call 911?

When a water pipe breaks, the initial thought process may include calling a plumber. 

While this is likely, according to Chism, the local plumbers may not be able to respond to a leak immediately. When there’s “inches of water” on the floor, it is an emergency, he added.

“These things are flooding buildings,” he said. “It’s causing fire alarms to go off because the water is getting into the electrical systems. It’s causing malfunctions across multiple systems, especially in these larger buildings.”

He added that most of the calls are not normal homes, though they do occur.

“You automatically think of a house, but it’s significantly less than we see in these larger, multi-family homes or these commercial buildings,” he said.

For example, the Jefferson County Detention Facility noticed leaking water Tuesday around 12 p.m. Inmates were moved and Jefferson County Sheriff’s Office maintenance workers climbed up into the ceiling, eventually finding that sprinkler system pipes had frozen and thawed, causing them to burst.

The water flooded throughout the facility, according to a video by the sheriff’s office, adding in a social media post that “stories like this are not uncommon for aging buildings.”

When the fire department responds to leaks, they often shut off the water and move on. 

“All of a sudden you see water gushing out of your ceiling, you may not know where your main shutoffs are. You may be worried its causing water and electricity to mix or affecting your gas,” Hafen said. “You reach out to your emergency services first because you have no idea who to call. The fire department gets the response because they have the ability to shut off water, electricity and gas to any property.”

“A lot of the time we don’t wait, especially when you see how busy we are,” Chism said. “We shut off the water and make sure everything is good and then we leave because we have another one to go to.”

Hafen said the Aurora Plumbing Company makes pipe breaks its priority during these times. The company offers customers experiencing other plumbing issues account credits if they are willing to delay their service so plumbers can respond to water leaks.

Chism notes that they often have “ridiculous numbers” of calls for response on the thawing days following the freeze because, when it’s that cold, there’s not much that can be done. 

What to do?

The classic tip of leaving faucets dripping during the cold still remains the gold standard of preventing pipe freezing, both the fire department and Hafen stated.

But keeping temperatures inside your home high can be crucial, as well.

Hafen said that though people may try to drop thermostat temperatures at night to conserve energy, it can lead to an array of issues.

“Don’t turn your temperature down on your home. Actually, turn it up a couple of degrees more than you are used to,” he concluded. “Don’t allow your home to cool down and heat up. Try and maintain the heat in your home at a constant temperature.”

Smart, eco thermostats may cause issues for people who aren’t home, according to Chism. He said that sometimes home temperatures drop when people are way because of the automatic thermostat. When they come back, they face breakages. 

Along with heating your home, Hafen said to open up cabinet doors during significantly cold days, especially plumbing cabinets. The opening allows latent air to flow through, instead of cold air remaining in the cabinets.

He also said to keep garage doors closed if there’s pipes inside or a bathroom above. If the garage is notoriously cold, he recommends using a space heater in the room.

“We’re only looking at a few days of freezing temperature, so the heat increase won’t really affect your bill,” he said. “But, if you drop your temperature and bust a pipe and flood your house, it’s going to cost you a lot more time and money than whatever you thought you’d save by turning your heat down.”

According to Angi.com, the average repair cost of a burst pipe in 2024 is $500, potentially stretching up to $5,000.

That doesn’t include the price of home repairs following water damage.