seal  Purdue News

July 11, 2003

Beware of contaminated well water due to recent flooding

WEST LAFAYETTE, Ind. – Water everywhere, but none safe to drink: That may be the concern of homeowners whose wells have been contaminated by floodwaters.

"Water from a well that has been flooded should be assumed to be contaminated," said Jane Frankenberger, an agricultural engineer at Purdue University. Purdue experts advise individuals not use well water for drinking, cooking, making ice, brushing teeth, or even bathing until satisfied that the water is not contaminated.

Frankenberger said floodwater can be contaminated by substances from upstream, such as sewage from flooded septic systems or wastewater treatment plants, manure, pesticides or fertilizer applied to cropland that was flooded. A septic system in the vicinity of a well also can cause contamination when the soil is flooded. Wells that are inside pits may be flooded even if the surface is not covered with water, Frankenberger said.

In order to ensure that the water is safe, the well should be disinfected, then the water should be tested to make sure pathogens have been completely eliminated.

To disinfect a well, well contractors or drillers may be contacted. In many cases, a homeowner can disinfect the well themselves. The Indiana Department of Environmental Management has an illustrated guide for disinfecting a well on the web.

Be sure to follow the instructions carefully, which include the following steps:

• Turn off electric power to the pump and remove the well cap.

• Prepare a bleach and water solution and pour the solution into the top of the well.

• Recirculate the water by connecting a hose to a faucet and spraying the water back into the well for at least 15 minutes.

• Open every faucet in the system and let the water run until the smell of chlorine can be detected, then close all the faucets and seal the top of the well.

• Allow the chlorinated water to stand in the system for several hours, preferably overnight.

• The following day, operate the pump by turning on all faucets, continuing until there is no chlorine odor.

Before you resume using the well, collect a water sample and have it tested by a certified laboratory. Call your county health department to find a laboratory near you.

Well disinfection will not provide protection from pesticides, heavy metals and other types of non-biological contamination, according to Purdue experts. If such contamination is suspected, due to the nearness of sources for these types of contaminants, special treatment is required. Homeowners can call the EPA Well Care Hotline at (888) 395-1033 if contamination by non-biological elements is suspected.

"Another implication flooding can have on your well is the damage or deconstruction of the well in general," said Brent Ladd, an Extension water specialist. Ladd said that fast moving floodwater can carry debris that could dislodge well construction materials or distort the casing. The coarse sediment in floodwater also could erode pump components.

Ladd advises homeowners to inspect the well for physical damage or look for signs of leakage. In the case of a damaged well, consult a licensed water well contractor to find out if repairs are needed.

Additionally, flooding can damage your well pump and electrical systems. If the pump and/or electrical system have been under water, Frankenberger said homeowners should not turn on the pump because of the potential danger of electrical shock or damage to your well or pump. Once floodwaters have receded and the pump and electrical system have dried, Ladd said not to turn on the equipment until a qualified electrician has checked the wiring system.

Individuals with flooded wells are encouraged to find an alternative source of water for drinking, cooking and washing. For example, one may be able to get water from a neighbor's well if you know it is safe, or from a public water supply. Purchasing bottled water also is a good alternative.

"If you can't find a convenient source of safe water, boil your well water for five minutes before use," Frankenberger said.

"Homeowners returning to their home after a flood may be anxious to use the water. But remember that flooding presents special health risks and requires extra attention to protect your family's health."

Homeowners also should reduce water use to protect their septic systems after a flood.

"Septic systems rely on an oxidizing environment or dry soil to purify the wastewater before it reaches groundwater," said Brad Lee, assistant professor of agronomy. "When soils are saturated, wastewater cannot be absorbed and filtered by the soil, resulting in a plumbing backup in the home or wastewater seeping onto the lawn."

Writer: Meggie Issler, (765) 494-8402,

Sources: Jane Frankenberger, (765) 494-1194,

Brent Ladd, (765) 496-6331,

Brad Lee, (765) 496-6884,

Ag Communications: (765) 494-2722; Beth Forbes,;

Related Web site:
Purdue Extension Safe Water Web site

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