Chloride in Drinking Water

Chloride is a naturally occurring element that is common in most natural waters and is most often found as a component of salt (sodium chloride) or in some cases in combination with potassium or calcium. The presence of chloride in groundwater can result from a number of sources including the weathering of soils, salt-bearing geological formations, deposition of salt spray, salt used for road de-icing, contributions from wastewaters and in coastal areas, intrusion of salty ocean water into fresh groundwater sources. In PEI, chloride levels in groundwater are relatively usually fairly low, but can become elevated in areas near the coast, or in areas of heavy salting of roads. 

What are the health concerns?

Chloride is considered to be an essential nutrient for human health and the main source of chloride is from foods, with drinking water making up only a small portion of normal dietary intake.  Chloride in drinking water is not harmful, and most concerns are related to the frequent association of high chloride levels with elevated sodium levels. There is no health based drinking water guideline for chloride however the Guidelines for Canadian Drinking Water Quality recommend and aesthetic objective for chloride levels of 250 mg/L, based on the potential for undesirable tastes at concentrations above this level, and the increased risk of corrosion of pipes. 

What are the treatment options?

Elevated chloride levels can sometimes be reduced by reconstruction of your well, or in other cases, by the use of a water treatment device, and it is recommended that advice from a qualified groundwater professional be sought prior to deciding what solution best meets your particular situation. The most common water treatment devices for reducing the chloride content of drinking water are reverse osmosis, anion exchange or distillation treatment systems. 

The Department does not recommend specific brands of treatment devices; however, it is recommended that consumers purchase devices bearing a label stating they are certified to NSF /ANSI Standard 58 (for reverse osmosis drinking water treatment systems), NSF/ANSI Standard 62 (for drinking water distillation systems) or for anion exchange systems, a device constructed with materials certified to NSF/ANSI Standard 61(for drinking water system components – health effects).  

As with the use of any drinking water treatment device, the effectiveness of treatment should be verified by sampling after installation. In addition, it is important to ensure the device is used and maintained according the manufacturer’s directions and its performance periodically confirmed by sampling.