Sat. Oct 1st, 2022
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 tubes are made of lead, iron and copper.
enlarge 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 tubes are made of lead, iron and copper.

Andrew Whelton/Purdue University, CC BY-ND

In 2020, when wildfires swept through the hills near Santa Cruz, California, toxic chemicals were released into the water supplies of at least two communities. One sample found benzene, a carcinogen, at 40 times the state’s drinking water standard.

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

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

The results, released Dec. 14, show how easily wildfires can cause widespread drinking water pollution. 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 chemicals to leak from the damaged plastics.

As environmental engineers, we advise communities on drinking water safety and disaster recovery. The extreme wildfire seasons in the western US are putting more communities at risk in ways they may not realize. This year alone, more than 52,000 fires have destroyed more than 17,000 buildings, many of which are homes connected to water systems. Heat-damaged plastic pipes can continue to leach chemicals into the water over time, and it can take months and millions of dollars to rid a water system of the contamination.

A mind-boggling source of contamination

The cause of drinking water pollution after wildfires has baffled authorities since its discovery in 2017.

After the Tubbs Fire of 2017 and the Camp Fire of 2018, chemicals were found in underground water distribution networks, some at levels comparable to hazardous waste. The contamination was not present in the water treatment plants or drinking water sources. Some homeowners found drinking water contamination in their plumbing.

Tests showed that volatile organic compounds had reached levels that posed immediate health risks in some areas, including benzene levels that exceeded the EPA hazardous waste threshold of 500 parts per billion. Benzene was found at levels 8,000 times the federal drinking water limit and 200 times the level causing immediate health effects. Those effects can include dizziness, headache, skin and throat irritation, and even unconsciousness.

The problem with plastic

Plastics are ubiquitous in drinking water systems. They are often less expensive to install than metal alternatives, which can withstand high temperatures but are vulnerable to corrosion.

Plastic water pipes don't have to burn to be a problem.
enlarge Plastic water pipes don’t have to burn to be a problem.

Andrew Whelton/Purdue University, CC BY-ND

Nowadays, underground water pipes and those for customer water meters are increasingly made of plastic. Pipes that transport the drinking water from the meter to the building are often made of plastic. Water meters sometimes also contain plastic. Private wells can have plastic well casings as well as buried plastic pipes that supply well water to plastic storage tanks and buildings.

Pipes in buildings that supply hot and cold water to faucets can also be plastic, as can faucet connections, dip tubes for water heaters, refrigerators, and lines for ice machines.

To determine whether plastic pipes could be responsible for drinking water pollution after wildfires, we exposed publicly available plastic pipes to heat. The temperatures were comparable to the heat of a wildfire radiating to buildings, but not enough to set the pipes on fire.

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

Benzene and other chemicals were generated in the plastic pipes by just heating. After the plastics cooled, these chemicals then leaked into the water. It happened at temperatures as low as 392 degrees Fahrenheit. Fires can exceed 1,400 degrees.

While researchers previously found that plastics can release benzene and other chemicals into the air when heated, this new study shows that heat-damaged plastics can leach dozens of toxic chemicals directly into water.

What to do in case of infection?

A community can prevent water pollution from spreading if damaged pipes can be quickly insulated. Without insulation, the contaminated water can move to other parts of the water system, through the city or into a building, causing further contamination.

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

Flushing heat-damaged pipes will not always remove the contamination. While helping Paradise, California recover from the 2018 campfire disaster, we and the U.S. Environmental Protection Agency estimated that some plastic pipes required more than 100 days of non-stop water flushing to be safe to use. Instead, officials decided to replace the pipes.

Even if a home is undamaged, we recommend testing the water in private wells and service pipes if there was a fire on the property. If contamination is found, we recommend locating and removing the heat-damaged plastic contamination sources. Some plastics can slowly leach chemicals such as benzene over time, and this can last for months to years depending on the extent of pollution and water use. Boiling the water will not help and benzene can get into the air.

Preventing Widespread Contamination

Communities can take measures to prevent contaminated drinking water in the event of a fire. Water utilities can install network isolation valves and backflow preventer equipment to prevent contaminated water from entering the utility’s plumbing system from a damaged building.

Insurance companies can use prices to encourage property and city owners to install fire-resistant metal pipes instead of plastic ones. Rules to keep vegetation away from meter boxes and buildings can also reduce the chance of heat reaching plastic water system components.

Homeowners and communities rebuilding after fires now have more information about the risks when considering 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 wildfire and residents had to evacuate again.The conversation

Andrew J. Whelton is an associate professor of civil, environmental and environmental engineering at Purdue University; Amisha Shah is an assistant professor of civil engineering and environmental and ecological engineering at Purdue University; and Krisstofer P. Isaacson is a Ph.D. Student at Purdue University

This article is republished from The Conversation under a Creative Commons license. Read the original article here.

Listing image by Andrew Whelton/Purdue University, CC BY-ND

By akfire1

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