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Our tests have now confirmed a source of these chemicals, and it is clear that forest fires are not the only flames that risk drinking water systems.

In a new study, we heated plastic water pipes commonly used in buildings and water systems to test how they would react to nearby fires.

The results, published on December 14, show how easily forest fires could cause widespread pollution of drinking water. They also show the risks when only part of a building catches fire and the rest remains in use. In some of our tests, heat exposure caused more than 100 chemical chemicals to rise from the damaged plastics.

As environmental engineers, we advise communities on drinking water safety and disaster recovery. The extreme forest seasons of the western United States risk more communities in ways they may not realize. Just this year, more than 52,000 fires destroyed more than 17,000 structures – many of them homes connected to water systems. Hot damaged plastic pipes can continue to lift chemicals into water over time, and removing a water system from the pollution can take months and millions of dollars.

Critical Source of Pollution

The cause of drinking water pollution after forest fires has dismayed authorities since it was discovered in 2017.

After the Tubbs Fire in 2017 and 2018 Fire Department, chemicals were found in buried water distribution networks, some at levels comparable to hazardous waste. Pollution was not in the water treatment plants or drinking water sources. Some homeowners have found drinking water pollution in their plumbing.

Tests have shown that volatile organic compounds have reached levels that posed immediate health risks in some areas, including benzene levels that exceeded the EPA hazardous waste disposal threshold of 500 parts per billion. Benzene was found at a level 8,000 times the federal drinking water limit and 200 times the level that causes immediate health effects. These effects can include dizziness, headaches, skin and throat irritation and even unconsciousness, among other risks.

Plastic water pipes don’t have to burn to be a problem. Andrew Whelton / Purdue University, CC BY-ND

This year, forest fires have triggered drinking water pollution in at least two additional California drinking water systems, and tests are still ongoing in other communities.

The Problem With Plastics

Plastics are ubiquitous in drinking water systems. They are often less expensive to install than metal alternatives that hold up against strong heat but are vulnerable to corrosion.

Today water pipes under the street and those that deliver water to customers ’water meters are increasingly made of plastic. Pipes that transport the drinking water from the subway to the building are often plastic. Water meters also sometimes contain plastics. Private wells can have plastic well enclosures as well as buried plastic pipes that deliver well water to plastic storage tanks and buildings.

Pipes inside buildings that carry hot and cold water to faucets can also be plastic, as can faucet connectors, water heaters, pipes, a refrigerator, and an ice hose.

Some common types of drinking water pipes: Black plastic is HDPE; white is PVC; yellow is CPVC; red, maroon, orange and blue are PEX; green is PP; and gray is polybutylene. The metal pipes are lead, iron and copper. Andrew Whelton / Purdue University, CC BY-ND

To determine whether plastic pipes could cause contamination of drinking water after forest fires, we exposed common available plastic pipes to heat. The temperatures were similar to the heat of a forest fire, which radiated to buildings, but was not enough to cause a fire from the pipes.

We tested several popular plastic drinking water pipes, including high density polyethylene (HDPE), bonded polyethylene (PEX), polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC).

Benzene and other chemicals were generated inside the plastic tubes only by heating. After the plastics cooled, these chemicals were then leached into the water. It occurred at temperatures up to 392 degrees Fahrenheit. Fires can exceed 1,400 degrees.

While researchers have previously discovered that plastics could emit benzene and other chemicals into the air during heating, this new study shows that heat-damaged plastics can directly lift dozens of toxic chemicals into water.

What To Do About Pollution

A community can stop the spread of water if damaged pipes can quickly become isolated. Without insulation, the contaminated water can move to other parts of the water system, across the city or inside a building, causing further pollution.

During the CZU Lightning Complex Fire near Santa Cruz, one water server had water distribution system valves that appeared to contain the benzene-contaminated water.

Washing heat-damaged pipes will not always remove the contamination. While we helped Paradise, California, recover from the 2018 Fire Disaster Disaster, we and the U.S. Environmental Protection Agency estimated that some plastic pipes would require more than 100 days of non-stop water washing to be safe for use. Instead officials decided to replace the pipes.

Different types of pipes react to heating in different ways. Andrew Whelton / Purdue University, CC BY-ND

Even if a home is undamaged, we recommend testing the water in private wells and service lines if a fire was on the property. If contamination is found, we recommend finding and removing the heat-damaged plastic pollution sources. Some plastics can slowly raise chemicals like benzene over time, and this could last from months to years, depending on the scale of pollution and water use. Boiling the water does not help and can release benzene into the air.

Avoiding Widespread Pollution

Communities can take steps to prevent contaminated drinking water in the event of a fire. Water companies can install mains isolation valves and backflow prevention devices, to prevent contaminated water from moving from a damaged building into the service pipe network.

Insurance companies can use pricing to encourage homeowners and cities to install fire-resistant metal pipes instead of plastics. Rules for keeping vegetation away from meter boxes and buildings can also decrease the chance of heat reaching plastic water systems.

Homeowners and communities rebuilding after fires now have more information on the risks as they consider whether to use plastic pipes. Some, like the city of Paradise, have chosen to rebuild with plastic and accept the risks. In 2020, the city had another forest scare and residents were forced to evacuate again.

Andrew J. Whelton is an Associate Professor of Civil, Environmental & Environmental Engineering, Purdue University.

Amisha Shah is Assistant Professor of Civil Engineering and Environmental and Environmental Engineering, Purdue University.

Kristofer P. Isaacson is a doctor. Student, Purdue University.

Communication statement: Andrew J. Whelton received funding from the Paradise Irrigation District and Paradise Rotary Foundation. He also participated in the Emergency Services Operation of California Governor Fire Water Task Force from January 2019 to May 2019. Amisha Shah received funding from the Paradise Irrigation District. Kristofer P. Isaacson does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has not disclosed any related affiliations beyond his academic appointment.

Returned with permission from The Conversation.