Where there’s smoke, there’s usually fire, unless there’s sewer testing nearby.  

Over the next six months, the San Antonio Water System will be smoke testing sewer lines over the Edwards Aquifer Recharge Zone, a requirement under state environmental codes. The testing is meant to prevent leaks of raw sewage over cracks and crevices that lead to the Edward Aquifer, the primary drinking water supply in the San Antonio region. 

The testing works by blowing zinc chloride-based smoke into a SAWS sewer main, which forces the smoke out of leaks in the private sewer laterals that lead to individual homes and businesses. 

So far, workers have blown smoke through 30 miles of sewer mains and found 54 defects over nearly three weeks of testing, said Jeff Haby, SAWS vice president of production and treatment. The utility plans to test 700 miles of sewer lines in 2019. 

On Thursday, crews with SAWS contractor Burgess & Niple were pumping smoke into a sewer main below Spring Club Drive on the Northwest Side. A plume of white smoke shot from a piece of broken PVC pipe sticking up from the grass in a front yard, the remnants of a sewer clean-out cap that looked like it had been broken off. 

“This is a classic, where it just gets hit with a lawnmower or something,” SAWS spokeswoman Anne Hayden said. 

A plume of smoke rises from a broken sewer clean-out cap as the San Antonio Water System conducts smoke testing over the Edwards Aquifer Recharge Zone.
A plume of smoke rises from a broken sewer clean-out cap as the San Antonio Water System conducts smoke testing over the Edwards Aquifer Recharge Zone.

When this happens, leaves, debris, and rainwater can get into the sewer. That can back up the house’s sewer line or wash into and overwhelm the SAWS system, leading to sewage leaks. 

When they find defects, crews mark them with flags, take photos, and send them to the property owner with a request to fix it, Haby said. Because most of the defects are broken clean-out caps, the fix is usually pretty simple – just replace it with another cap. 

“Take a picture, send it back to us, and you’re done,” Haby said. 

Across the street, similar smoke plumes rose from the cylindrical vents poking up from the roofs of the street’s one-story ranch homes. That indicated the sewer line was free of leaks.  

“That’s what we want to see,” Haby said. “That means the people’s system is performing right. All the P traps are blocked and the sewer gas is coming out the roof vents.”

Occasionally, the traps built into home plumbing dry out, Haby said. That’s especially true in large homes where the occupants don’t use every bathroom regularly. In those cases, residents could see the smoke rising from a drain. 

“There’s nothing to prevent the smoke from going in the house,” Haby said. “That’s the biggest challenge we’ve got. If we do that, people are very upset with us.”

SAWS has been holding meetings, sending letters, and posting door hangers to let people know when their area is set for testing, he said, adding that most people fix their lines after learning they have a leak. 

“Most people realize this is the recharge zone, it’s in the best interest of them and their family to protect the water quality of the Edwards Aquifer, so most people will comply,” he said. 

Brendan Gibbons

Brendan Gibbons is a former senior reporter at the San Antonio Report. He serves as the assistant manager of the Greater Edwards Aquifer Alliance.