ATHOL — The Department of Public Works has dealt with a series of water main breaks over the past couple of weeks and DPW Director Dick Kilhart thinks he may have an idea what’s behind the failures.

The most recent breaks, he said, have happened in the wake of fires to which the Athol Fire Department has had to respond.

“I’m not going to suggest that there’s a correlation there,” Kilhart said, choosing his words carefully, “but we had a fire on Freedom Street on Sunday night last week, Sunday night into Monday morning. We had a water break across from the YMCA on Tuesday. Then we had a water main break Thanksgiving evening on South Main Street, not too far from that location.

“What happens,” he explained, “is every time you open or close a valve — whether it’s a fire truck, whether it’s a hydrant, whether it’s a business that has a fire sprinkler system let go — and then they close it suddenly, it creates an ocean wave, what we call a ‘water hammer.’ And then that ocean wave slams through the system at a pressure much greater than what the system pressure is.”

He said the wave could in fact double the pressure normally sustained by the system’s water mains.

“So, if you have 100 pounds in there normally,” Kilhart continued, “that could be one and a half times that, or you might have 200 pounds slamming up against a dead end, which might be a closed hydrant, a closed valve, something of that nature.”

Kilhart noted the breaks were definitely not caused by the recent installation of new water mains in the area of Kennebunk and Green streets.

“Actually,” said Kilhart, “by doing that project, we have reduced the pressure by a couple of pounds; not a lot — by 2 or 3 pounds (per square inch).”

The recent break in front of the Athol Area YMCA occurred in a 12-inch line that feeds water up from the South Street well via a line running through the Lord Pond Plaza. “So, if they’re hooking on hydrants in and around that area, you’re kind of thinking to yourself that might be what’s happening. That pipe (near the Y) is probably 100-plus years old.

“What was concerning to me, too,” Kilhart continued, “was the second one Thanksgiving afternoon and evening, over in front of the old Butler’s (Decorating Center on South Main Street), that was actually 6-inch steel — rugged pipe — with a hole about 6 inches around blown out of the bottom. That’s definitely created by a water hammer, not by some external force. Yeah, you’re four days removed from a fire, but again, you could still have some oscillation going in there, and if you get air trapped in there at all it lets go.”

The third recent break, also on South Main Street, was bound to happen, said the DPW director.

“It was in a valve box that goes into the fire line into the (NAPA) Auto Parts store,” Kilhart said, adding that some bolts that held a flange in place on the box were completely rotted. “Ultimately, I think that one would have happened anyway because of the condition of the bolts.

“It might have been nice if that was maybe at a different time, rather than the third one in one week, but it’s better than the middle of January.”

Kilhart credited his team for working in temperatures in the low to mid-30s on a holiday.

“They worked hard. They worked late on Thanksgiving night,” he said.

He also said residents of the area responded very well, understanding the need to interrupt water service and even bringing hot coffee to the crew. The job was finally completed Friday evening.

Kilhart was quick to point out that he wasn’t blaming the Fire Department for the recent problems, pointing out “they have a job to do, too. When you’re moving water quickly and you close that hydrant quickly, you can’t prevent it. It literally creates an ocean wave that keeps moving until it gets to the end of the system.”

The problem could be solved to a great degree if the town were able to build a water tank somewhere on the west end of Athol. The tank, he said, would allow for surge control because tanks are vented at the top.

“The ocean wave would push all the way to that tank and would vent into the atmosphere. But now, it has no other place to go. Sometimes, those old hydrants close so quickly and sometimes you can’t help that,” he said.

Kilhart said the town has a surge control pressure release valve on Pheasant Lane and has talked about the possibility of adding others to the system during the next construction season.

So far this year, said Kilhart, the town has experienced a total of 11 water main breaks, with the average usually being around six or seven. He said much of the cast iron piping used for Athol’s water mains is “way beyond its useful life,” which, he said, was about 100 years.

“It’s implausible to think we could afford to replace all of it all at once,” he said, “so we have to take in bits and pieces.”