Massive Flow Creates Crazy Positive Pressure

Texas plumbers follow their noses to find source of building odor
Massive Flow Creates Crazy Positive Pressure

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A storage tank on the roof of a 660-foot building with a float switch that had broken loose from the mount created some crazy positive pressure in a Texas sewer main earlier this month.

“It was bubbling up through the toilets inside on the bottom floor,” says Phil Little of Primo Plumbing in San Antonio, Texas. “We get a lot of positive pressure in downtown sewer mains in San Antonio anyway, but nothing like that. According to maintenance there had been a smell for a while, but never anything this bad.

So we started following our noses and found a manhole with what looked like a 36-inch sewer main and it was just rolling with water – more flow than what it should be – and pushing air out of that manhole. It was crazy. There were some 6-inch traffic lids and it was rattling those around.”

The tank, fed by a 3-inch pipe, has a 3-inch overflow main but the tank had no high-water alarm and was not visible without access. Little, a master plumber with 25 years of experience, said the water had been flowing for two days.

“One of our plumbers repaired the float switch and that stopped the pressures from the sewer,” he says. “That’s the first time I’ve seen something that bad.”

A high-water alarm also was installed in the tank to prevent a future occurrence.

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