Do-It-Yourself Rodent Control

What Happens When Your City Is Flushing Its Water Mains?

Once or twice a year, the city sewer crew comes through your neighborhood and places a cardboard announcement sign on your front door. It tells you that they are planning to "flush the water mains" on a certain date and at a certain time. Then the card instructs you to avoid using toilets, sinks, showers, dishwashers, and washing machines at that time. So, what exactly is "flushing the mains"? Is it a sewer cleaning? What does it do, exactly? Here is more info on that so you can understand why the city has informed you and instructed you not to use water at that time.

​What "the Mains" Are

In city sewer lines, "the mains" are the main sewer lines. They are the primary sewer lines into which everything else flows, and the main lines carry all waste and wastewater to the water treatment facility. Because they are the main sewer pipes, they tend to get clogged and extremely disgusting over time. To alleviate these issues, the city needs to clean these sewer lines. So, yes, in effect, flushing the mains is a sewer cleaning of sorts.

​Flushing the Mains: What Happens

​To flush the mains out, and to remove clogs and backed-up fecal matter, the city pumps a massive amount of water through the lines. It builds up water pressure at one point behind a wall in the sewer and then opens the flood gates of that tunnel, creating a very powerful rush of water. The force flushes the main line, pushing the blockages out of the way and moving stuck waste farther on down the line where it is supposed to go. 

In order to create the correct amount of pressure, all water lines going to homes and businesses are restricted from drawing water. The intense pressure and the extra water drawn from residential and commercial sources is a literal hydro-blast. You can experience the reverse effect on your end, should you attempt to flush a toilet or turn on a faucet while the city is creating this big, highly pressurized water explosion. The faucet will rattle, gurgle and then forcefully squirt water, while the toilet will strain to flush fully. Then the toilet will not refill the water tank, either. This whole process continues for at least an hour, or until it is determined that the main line on your street has been successfully cleaned and cleared.