Water utilities are flushing pipes to clean drinking water after the fires. Here’s what to know

Just how much did the deadly L.A. wildfires affect the water supply? It’s an issue the Los Angeles Department of Water and Power and other utility providers are learning about as they work to restore reliable and safe water to neighborhoods.

During the fires, multiple areas were put under Do Not Drink or Do Not Use water advisories. And while many have been lifted, contamination is still a concern. Pipe flushing and testing is the primary way utilities are resolving this issue — which may take a month to complete. We breakdown what residents should know.

What is flushing?

The LADWP is doing rounds of pipe flushing and testing in hopes of lifting the Do Not Drink notice that’s still in effect for Pacific Palisades residents in and around the 90272 ZIP code. Lincoln Avenue Water Company, the Rubio Canon Land and Water Association, and the Las Flores Water Company are also taking similar action.

Jonathan Leung, director of water quality at LADWP, said the fires affected nine zones that have about  8,400 service connections. Flushing the system should eventually resolve the issues there, which works by opening valves and purging water at a high velocity, usually through a fire hydrant. It’s done in tandem with testing.

He said LADWP is following a method called “unidirectional flushing” that takes into account the water’s natural downstream flow. It’s like sweeping a room where you start from one corner and push all the things you’re sweeping toward a dustpan.

“That’s kind of the same concept with the pipe flushing," he said. "You’ll kind of start from one end and then continue to operate valves in succession to push all the water towards one direction."

Flushing moves air and sediment out of the system, which can get in during the high water demand of firefighting. Leung said during the fires, water velocity in their pipes went from a normal range of 2 to 4 feet per second up to 14 or 15 feet per second.

“At that type of high velocity, you do run the risk that different things that might be in pipe networks, even some of the lining, all get disrupted,” he said.

Flushing also helps to bring in fresh water and a low amount of disinfectant, which water utilities are required to have in their systems to prevent bacterial growth.

How residents can do it

Leung said that while the utility is doing pipe flushing of the mainlines, residents should also do it at homes that are still standing. Here’s the utility’s step-by-step guide to doing it yourself:

1. Prepare your site for flushing: Remove aerators and screens from all faucets. [Note: Aerators are small attachments that create a constant water flow rate.] Set water-softening devices and filters, both point-of-use and whole-house, to “bypass mode.”
2. Flush outside plumbing: Open and flush any external fixtures and hose bibs until water is clear and temperature is constant.
3. Flush cold water: Run all cold-water faucets on the property beginning with the faucet closest to the water line. Let all run at the highest flow (or fully open) until water is clear and temperature is constant. Then turn off all faucets in reverse order. 
4. Flush all toilets and urinals: Do this at least once, but repeat if the refilled water is not clear.
5. Flush hot water: Drain your hot water tank to discharge any accumulated sediments. Wait for the hot water tank to refill and flush as in Step 3.
6. Clean aerators and screens and reattach to faucets, shower heads, and fixtures.
7. Flush any water-using appliance or run a cycle. This includes the washing machine, dishwasher, and refrigerator/ice maker.
8. Restore all removed filters and reset all water devices from “bypass mode.”

What about testing?

Leung said the main thing they’re testing for is volatile organic compounds or “VOCs,” essentially toxic chemicals that can be found in products like paint thinners, cleaning supplies, and some craft materials. VOC amounts in water are regulated by the state under Title 22. Utilities are also checking for proper levels of disinfectant, the carcinogen benzene, and bacterial contaminants.

A summary of results will be posted on the utility’s website when it’s available. You can track LADWP’s progress with flushing and testing here.

Utilities follow a sequence of testing. Depending on what’s found, testing and flushing may have to be repeated to ensure water quality meets state standards.