Lead Control Program
When did you begin the Orthophosphate Program?
We began adding orthophosphate to the water supply in June 2000 to control lead levels in Winnipeg's tap water.
Why did you select orthophosphate?
We selected orthophosphate because it is safe and economical. It is the most efficient way to reduce lead to levels below the national guideline. The program was approved by both Manitoba Health and Manitoba Conservation. It follows the Public Health Act. Several cities in the United States and Canada use orthophosphate to control lead in tap water.
How does orthophosphate reduce lead levels in the water?
Orthophosphate works by forming a protective coating inside water pipes. This coating helps reduce corrosion that can add lead to the water supply. We add orthophosphate in small amounts in the form of food-grade phosphoric acid. Phosphoric acid is a clear, odourless liquid. By weight, it is 65% oxygen, 32% phosphorus and 3% hydrogen. It is found in many popular food products, such as soft drinks.
You would need to drink more than 100 glasses of tap water to get the same amount of phosphoric acid that you would get in one glass of most colas.
How much orthophosphate do you add to the water?
We add orthophosphate at a rate of 2 parts per million.
Does orthophosphate change the chemistry of the water?
Yes, a little. As we add orthophosphate to the water, the pH drops about 0.1 units below normal. This means that the alkalinity is reduced by less than 2 parts per million.
Do you check to see if the Orthophosphate Program is working?
Yes. Since May 2000, we have monitored the program using:
- a lead loop piping system
- a volunteer sampling program
Besides indicating the average amount of orthophosphate added since the program began, the test results in the graphs below show that the average amount of lead in both the volunteer and lead loop water samples are normally below the guideline. It indicates that the program is working, as no results since 2002 have exceeded the Health Canada national guideline for lead of no more than 0.01 parts per million.
We currently monitor the program with a lead loop piping system designed to replicate a lead water service to a home or building. We started reporting with this system as of January 1, 2010, however, it's been in use since June 2006.
Results from June 2006 to December 2017
Average five minute flush lead concentration in lead loop system with lead service connections
Before switching to the current lead loop monitoring system at the beginning of 2010, we used a sampling program with homeowners who had lead pipes serving their homes. Between 8 and 20 volunteer homeowners helped us by taking water samples from their tap once a month. From May 2000 to December 2009 we collected the samples and analyzed them for lead.
Results from May 2000 to December 2009
Average five minute flush lead concentration at single-family homes with lead service connections
What is the annual cost of adding orthophosphate to the water supply?
It costs about $200,000 annually to operate the Orthophosphate Program.
Are there any other benefits to adding orthophosphate to the water?
Yes. The protective coating inside the water pipes provides other benefits including:
- extended life of household plumbing
- extended life of water-using appliances, such as hot water tanks
Do you monitor the impact of the Orthophosphate Program on the environment?
Yes. Much of our water supply ends up as sewage at the three wastewater treatment plants. Here it is treated and released to the Red and Assiniboine Rivers. Since we started the Orthophosphate Program, results of wastewater tests show:
- the phosphorus levels haven't changed much at the South End and West End plants
- the phosphorus levels are about 14% higher at the North End plant
- the phosphorus levels have decreased about 8% in biosolids
- the lead levels have decreased about 37% in biosolids