"You see," Elias explained as he began hooking up his gauges, "if a fire truck connects to a hydrant down the street, it can pull water backward. Without this valve, fertilizers from your garden or chemicals from a hose could end up in your neighbor's tap."
He manipulated the bypass valves, equalizing the pressure. He watched the gauge.
He moved to the second check valve. This was often the trouble spot. Sand, debris, or just a tiny piece of grit could hold the valve open just a fraction of a millimeter. If the needle dropped, he’d have to strip the whole unit down.
He knelt by the green box and opened the lid. Inside sat the Double Check Valve Assembly. Its job was simple but critical: to ensure that if the water pressure in the main street pipe suddenly dropped, the water from the garden hoses or irrigation system wouldn't suck back into the town's drinking supply.
"It's a solid install," Elias said, handing her the copy of the test report. "I’ll upload the results to the council portal right now so you’re in the clear."
Backflow is the unwanted reverse flow of water from a potentially contaminated source back into the clean, treated water supply. This typically occurs due to two main reasons:
He grabbed his toolbox and the testing kit—a complex arrangement of hoses and gauges that looked like something from a science fiction movie.