How to Fight Saltwater Intrusion on Water Wells
Saltwater intrusion occurs naturally along the thousands of miles of U.S. coastline, though it is exacerbated by climatic events and increased water demand driven by population growth.
With the number of Americans living in coastal counties expected to reach 49 percent of the U.S. population by 2020, according to the National Oceanic and Atmospheric Administration (NOAA), increased demand will put additional pressure on water tables and disrupt the delicate groundwater/saltwater balance.
When saltwater intrusion occurs in water wells, water quality is adversely affected, causing an unpleasant taste. Intrusion also increases the corrosivity of the water, which can damage household plumbing and appliances. It also poses problems for the well pump by deteriorating pump parts that could leach metals into groundwater and degrade pump performance.
Increased water demand over the last 150 years is depleting prehistoric water resources across the United States, meaning well drillers might have to drop a pump many times deeper into a well than originally intended to hit the water table. It’s important for well drillers to know the effects on well pumps to ensure safety, continued performance and long pump life.
In deeper wells, submersible pumps are more effective than smaller jet pumps, yet the deeper submersibles go, the harder they must work to maintain the same amount of flow. The solution is to add stages to the pump assembly to increase the amount of pressure and power. If the well deteriorates enough, then it is possible the pump’s flow will be pushed left toward shutoff. And if there is not enough flow through the pump’s bowl assembly, thermal recirculation will occur, which can cause serious damage to the pump.
If the water table drops to the point where the pump is not reaching the groundwater or loss of prime, well drillers have the opportunity to plug the well and drill a new one in another location — or, if there is room and conditions are right to do so, drill a deeper well and increase horsepower by adding stages to the pump. Dropping a submersible pump and motor deeper into the noncoastal well casing requires precision in accordance with American Water Works Association (AWWA) standards for water wells. In a several-hundred-foot-deep well, for example, pipe that bends and turns puts undue stress on a vertical turbine submersible pump and motor, decreasing performance and potentially causing damage and failure.
Combatting Chemical Reactions
Twenty-five states have been identified by the United States Geological Survey (USGS) as having a high prevalence of potentially corrosive groundwater. Corrosive groundwater, if untreated, can dissolve lead, copper and other metals from pipes, pumps and plumbing fixtures. Though the use of lead in plumbing systems has been outlawed since the enactment of the Safe Water Drinking Act of 1986, plumbing that was installed before that time might contain lead — most notably in the solder used to join pipes.
Some manufacturers, including Xylem’s Goulds Water Technology, have retooled the manufacturing process of their residential pump products to meet stringent lead requirements. In fact, some Goulds Water Technology products have been engineered with stainless steel since 1994 to ensure they contain less than 1⁄20th of 1 percent lead.
If a pump impeller and bowl assembly are made with dissimilar metals such as bronze and cast iron, saltwater intrusion can wreak havoc on those metals through a galvanic effect. The saltwater attacks the metals, causing corrosion on one while the other deteriorates, contaminating drinking water in the process. Manufacturing pumps using homogenous materials, such as stainless steel impellers and bowls, helps minimize that effect.
However, if diluted freshwater and seawater stagnates for any period of time, such as after a hurricane or flood, this brackish water can have a destructive effect on even corrosion-resistant materials. This can cause the material to pit and corrode, eroding pump performance. The Pitting Resistance Equivalent Number (PREN) is a measure of the relative pitting corrosion resistance of various types of stainless steels in different caustic environments. Higher PREN values indicate greater corrosion resistance.
With maintenance, testing and treatment of private water supplies the sole responsibility of each homeowner, well drillers can help educate customers on basic testing to help ensure safe drinking water in the home.
In the event of a natural disaster — such as last year’s Hurricanes Irma and Harvey — well drillers should encourage homeowners to schedule well and pump maintenance as soon as possible as a precautionary measure.
In the aftermath of Hurricane Harvey, Texas homeowners with private wells that were flooded were advised to assume their well water was contaminated until tested. Besides saltwater intrusion, floodwaters might contain manure, sewage, bacteria, chemicals and other contaminants.
Following flooding, homeowners are often advised to put bleach in their wells to kill bacteria from fouled floodwaters. However, bleach and other additives intended to clean wells can have devastating effects on a well pump, so make sure to check with the pump manufacturer before pouring any chemicals into a well.
In the event of a mystery pump failure, manufacturers such as Goulds Water Technology encourage well drillers or homeowners to send the pump to their lab for analysis. The pump is only one piece of the puzzle; sending in a sample of the water will help investigators determine the root cause of the pump failure.
In addition to advising customers on best practices for well and pump maintenance, well drillers can seek out additional educational opportunities to stay up to date on technological advances and practical application in the field. For more information on continuing education courses offered through the Goulds Water Technology Factory School and GWT’s e-Learning virtual education program, visit http://goulds.com/factory-school and http://goulds.com/e-learning.