Treating Arsenic in my Home Well Water Supply

If you live in New Hampshire and use water from a bedrock well, your home’s water supply has about a one in five chance of containing at least a small amount of naturally occurring arsenic. Because New Hampshire’s bedrock is highly fractured, one well can test positive for arsenic contamination, yet another well 50 feet away may not. The problem is variable throughout the state, so the NH Department of Environmental Services recommends testing wells every three years for arsenic, as well as other common naturally occurring contaminants, like radon, lead and copper.

New Arsenic Standards For Drinking Water

From 1975 to 2001, the Environmental Protection Agency regulated that drinking water should have less than 50 parts per billion of arsenic. At the time, health risks caused by exposure to lower levels of arsenic were not recognized, but after further review, new standards were adopted in 2001.

Under these new standards, EPA set a goal of zero arsenic in U.S. drinking water. It also set an arsenic level limit of 10 parts per million based on research showing negative health effects from long-term exposure. Studies have shown that repeatedly drinking water with arsenic during a person’s lifetime can lead to cancer and other chronic ailments, such as cardiovascular or neurological disorders.


The naturally occurring arsenic in New Hampshire waters usually are found in one of two forms: Arsenic-III and Arsenic-V. These two forms have a slightly different chemical make-up and therefore it is important to know which kind – or if both – are present when selecting a water treatment system. Some systems can reduce both forms of arsenic, but their ability to remove Arsenic-II is not as effective. Our Skillings & Sons technicians can discuss with you the difference between the types of arsenic and how that affects your treatment options.


Once testing is done to determine the type of arsenic in your water, you must decide if you want to treat the water as it comes into your home or at the point of use. Treating water at the point of entry is often used when other minerals or contaminants are in the water, such as iron, manganese, bacteria or radon. It is recommended in homes where the water supply has arsenic levels above 250 parts per billion. Below this level, the risk of skin absorption is low. Point-of-entry systems are more expensive than point-of-use systems, so if arsenic levels are low, point-of-use may be the better option.

Installing filters on faucets at the kitchen sink or other places you draw drinking water is called a point-of-use treatment. These filters should be installed wherever water is taken for drinking, cooking or making ice. If there are no other contaminants in your water, this method is a simple and cost-effective way to reduce arsenic.

In a reverse osmosis filtration system, water flows through a membrane, filtering out some of the contaminants in the water. These molecules, plus some water, are flushed into your home’s wastewater system. The treated water is stored in a small storage tank until needed. When used to filter only the home’s drinking water at the point-of-use, this is the most economical option.

Oxidation filtration is one option for whole-house water filtration. A filter oxidizes iron and arsenic in the water and removes both kinds of arsenic as well as iron. Like other point-of-entry systems, the effectiveness of the treatment depends on the characteristics of your home’s water supply.


To make sure your water treatment system is working effectively, continual maintenance and testing is recommended. In the first year after installation, quarterly testing is recommended. In later years, semi-annual testing will ensure arsenic levels are below dangerous levels.

Skillings & Sons can discuss which tests you should consider and help you decide which filter system is right for your home. Contact us today.