The City of St. John’s has been receiving complaints of intermittent discoloured water over the past several weeks from residents that get their drinking water from Petty Harbor Long Pond (see service area map and list of streets).

It has been determined that the cause of the discoloured water is due to elevated levels of manganese.

The City of St. John’s first measured manganese increases in the raw water at Petty Harbour Long Pond on July 25, 2018.  This seasonal variation has been observed in previous years.  Since the beginning of August, some residents serviced from Petty Harbour Long Pond have reported sporadic episodes of discoloured water that eventually clears.

What is the City doing to address the issue at Petty Harbour Long Pond? (August 28, 2018)

  • We have notified the Provincial Government Water Resources and Public Health Departments of the elevated levels of manganese.
  • The Petty Harbour Long Pond Treatment Plant is not designed to effectively remove manganese, so the City is consulting with treatment process experts to develop an interim method of treatment for manganese removal and then plan on how to remove accumulated manganese in the distribution pipes.
  • The City continues to monitor the bacteriological health of your drinking water by continuous monitoring of the treatment process at the treatment plant and by collecting distribution samples for bacteriological analysis.  All samples are tested for adequate chlorine residuals and are sent to the Provincial Health Laboratory for analysis.
  • Water stations have been set up. If you are collecting water for your home, please ensure that you collect and store it safely using these tips from the Provincial Government.

Where can residents get more information?
Information on manganese in drinking water can be found on the Health Canada website:

Information on the proposed changes to the Health Canada Drinking Water Quality Guidelines for manganese can be found at:

If you have further questions or concerns about reported manganese levels in Petty Harbour Long Pond drinking water, please contact the City’s Access Centre by dialing 3-1-1 or 754-CITY (754-2489).


Manganese is an essential nutrient that is found in air, food, consumer products, soil and drinking water. Food is the main source of exposure to manganese, however manganese is more easily absorbed by the body from drinking water than from food.

What health effects can result from exposure to manganese in drinking water?
Although humans need to ingest small amounts of manganese to be healthy, too much manganese in drinking water could lead to some health effects, primarily on the nervous system. When exposed to high levels of manganese, infants may develop learning and behavior problems, while older children and adults may have problems with memory, attention, and motor skills. However, these effects would be hard to notice and may have other causes.

What are acceptable levels of manganese?
Health Canada has also set a Maximum Acceptable Concentration (MAC) of 0.10 mg/L at anytime.  The MAC is based on health effects for infants (0-1 years). 

The Canadian Drinking Water Quality Guidelines issued by Health Canada has set an aesthetic (visual) objective of 0.02 milligrams per litre (mg//L) in drinking water.  Concentrations of manganese in drinking water exceeding 0.02 mg/L may cause water to be discoloured, have bad taste and stain plumbing fixtures. 

Some of our samples have exceeded the Maximum Acceptable Limit of 0.10 mg/L so the City of St. John’s is advising residents serviced by the Petty Harbour Long Pond system to use an alternative source of water for making baby formula, baby food or for giving water to children under one years of age. 

According to Health Canada, infants are at greater risk from manganese in drinking water than children and adults because their brains are developing rapidly, they drink more water based on body weight and they absorb more manganese and are less able to remove it from their bodies. Formula-fed infants get enough manganese from the formula itself to meet their dietary needs. However, if their formula is reconstituted with water that contains manganese at levels above the guideline, they may ingest manganese above the recommended amount for nutrition. There is no concern for breast-fed infants.

Why was the guideline for manganese in drinking water revised?
Manganese has long been considered to only be an aesthetic concern in drinking water, responsible for staining fixtures and laundry. However, new scientific studies are showing health effects related to exposure to high levels of manganese in drinking water. Other studies show that the human body absorbs more manganese from drinking water than from food. This new information was used as the basis for the new guideline for manganese in drinking water, in order to protect the health of Canadians.

The guideline was established to be protective of the most sensitive population, which is formula-fed infants. If the manganese level in your drinking water is above the guideline, you should consider using an alternate source of water to reconstitute infant formula. For adults and older children, who drink less water based on body weight than bottle-fed infants, short-term exposure to manganese in drinking water slightly above the guideline is not a concern. However, if this is a long-term situation, a permanent solution such as the use of a treatment device or an alternate source of drinking water should be considered.

If levels of manganese in my water are above the guideline value, can I still use it to bathe and shower?
It is safe to bathe and shower in water with high levels of manganese as it will not enter the body through the skin or by breathing.

If levels of manganese in my water are above the guideline value, can I use it to cook with and brush my teeth?
It is safe to use water containing manganese slightly above the guideline to prepare food for adults and older children and for brushing teeth. Formula-fed infants get enough manganese from the formula itself to meet their dietary needs. If the manganese level in your drinking water is above the guideline, you should consider using an alternate source of water to reconstitute infant formula.

Can I tell if there is manganese in my drinking water?
Water that contains manganese may be colored, but not always. It would not have a distinct smell or taste. The only way to determine if manganese is present in your drinking water is to have it tested either by your municipality or by an accredited laboratory. Monitoring results from the City of St John’s indicate that when the water is clear, manganese levels are below Health Canada’s maximum acceptable concentration.  The city will continue to monitor the levels to ensure that this remains unchanged.

Are there treatment devices that I can use to remove manganese from my drinking water?
There are residential treatment devices that are capable of removing manganese from drinking water. These devices use a technology called reverse osmosis (RO) that would be able to remove manganese. Such devices need to be installed at individual taps and cannot be used to treat all the water entering the home. Health Canada recommends that consumers use devices that have been certified as meeting the appropriate NSF International/American National Standards Institute (NSF/ANSI) standard for drinking water treatment units by an accredited certification body. These standards have been designed to safeguard drinking water by helping to ensure the material safety and performance of products that come into contact with drinking water. Although there are currently no such devices certified to remove manganese, RO devices that have been certified to remove other metals (such as arsenic or lead) would also remove manganese.