Corrosion Control

The goal of the Corrosion Control Program is to reduce the amount of lead in tap water. This will help protect Hamilton citizens from the potential health impacts of lead. Corrosion control is required by the Ministry of the Environment, Conservation and Parks (MECP) Safe Drinking Water Act.  

Three options for corrosion control were identified and evaluated:

1. Lead service line replacement​​​
   The City continues to work with homeowners to replace lead pipes with the Lead Service Replacement Program and the Capital infrastructure replacement work. Based on the current replacement rate and uptake from residents, it will take 25 to 40 years to remove all the lead water lines in Hamilton. Lead service line replacement alone will not protect residents from lead exposure from lead-based fixtures and lead solder.
2. pH and / or alkalinity adjustment
   Due to the water quality of the treated water, it was determined that pH adjustment by chemical addition alone will not significantly control the release of lead from pipes, fixtures or solder.
3. Phosphate-based inhibitors
   Corrosion control with a phosphate-based inhibitor offers a solution to protect Hamilton Water customers from all contact sources of lead (pipes, fixtures and solder) in drinking water. A protective barrier is created inside the pipes which reduces the release of metals, such as lead and copper from household plumbing. This is important for those who cannot afford to replace the private-owned portion of their lead pipe, and those with newer homes that do not have lead supply pipes but still have leaded-brass fixtures and lead solder in their internal plumbing.

On November 25 2015, Council approved the use of orthophosphate, a phosphate-based inhibitor in the drinking water process to protect residents from the release of lead into the drinking water.

Phosphoric acid is commonly added to food and drinks to make them more acidic. The phosphoric acid is approved safe for use in municipal drinking water by the NSF. Phosphoric acid is a clear, odourless liquid that changes to orthophosphate under the general water chemistry conditions of Hamilton’s drinking water. Orthophosphate creates a protective barrier on plumbing surfaces that reduces the release of metals, such as lead and copper from household plumbing.

The UK began using orthophosphate to control corrosion and reduce lead in drinking water over thirty years ago.  In the UK, 95% of drinking water supply systems use orthophosphate. Phosphates (phosphoric acid, orthophosphate) are used in Canada, the United States, and Europe as a method for reducing corrosion in drinking water systems.

Implementation began on November 7, 2018 at the Woodward Water Treatment Plant, which provides water to most of the City of Hamilton. It will take time for orthophosphate to build up a protective barrier throughout the entire Woodward distribution system and linked plumbing surfaces. A monitoring program is in place to assess the effectiveness of orthophosphate and its performance in the system for lead control.

Orthophosphate will not be present in the drinking water of well-based communities of Lynden, Carlisle, Freelton and Greensville. The sampling program for the communal well systems revealed sample results below the Ministry of the Environment, Conservation and Parks (MECP) threshold. Therefore they do not require a Corrosion Control Program.

In October 2024, Hamilton Water began the first phase of reducing the orthophosphate concentration towards a lower maintenance dosage with the current orthophosphate concentration set at 1.9 mg/L. Hamilton Water continues to monitor and adjust water treatment operations to bring lead concentrations at the tap below the Maximum Allowable Concentration (MAC) of 10 mcg/L.

A Corrosion Control Pilot study was conducted and peer reviewed to ensure that the most appropriate phosphate-based additive was chosen.  Lead pipes were removed from the ground of Hamilton properties and used in the Pilot study. The two year study determined which type of phosphate treatment additive (phosphoric acid or orthopolyphosphate), concentration and conditions would be best for lead control.  

The City developed a monitoring program upon approval of the Corrosion Control Program to:

• measure the success of the corrosion control program
• ensure a stable level of lead protection is achieved

For more details on the City’s monitoring program please review the annual Corrosion Control Evaluation Report(PDF, 1.86 MB)

After the drinking water is used in the home, much of that water returns as wastewater or sewage to the Woodward Wastewater Treatment Plant or the Dundas Wastewater Treatment Plant. There, it is treated to remove additional phosphorus before being released into Hamilton Harbour.

The construction cost to implement corrosion control at the Woodward Water Treatment Plant was approximately $4.57 million and the annual operating cost currently averages $330,000.

Lead is a naturally-occurring metal and was used extensively for thousands of years in a wide range of household products, including plumbing materials and paint.  Lead is toxic to humans.  Ongoing exposure to even small amounts of lead can be harmful to human health, especially for babies, young children and women planning a pregnancy and pregnant women. Children absorb lead more easily than adults. Pregnant women and women planning a pregnancy can pass lead built up in their blood and bones to their unborn baby during pregnancy. Lead can affect developing babies causing premature birth, lower birthweight, decreased intellectual development, learning difficulties and reduced growth. 

Chronic exposure to lead can cause:

• Nervous system and kidney damage
• Learning disabilities
• Attention Deficit Disorder

When orthophosphate is present in the drinking water system it forms a protective coating inside pipes and household plumbing fixtures. This coating reduces the release of metals, such as lead and copper from household plumbing into the drinking water.

Yes, phosphoric acid is a tasteless, odourless, food-grade additive derived from a natural source of mineral rock that has been used for years by many water systems to control corrosion. The phosphoric acid changes to orthophosphate when it’s added to drinking water. The orthophosphate will be monitored and controlled to be between 1 mg/L to 3 mg/L as part of the City of Hamilton’s water treatment process. The proposed concentration of orthophosphate present in drinking water is in-line with general industry practice, and would be one of many sources of phosphorus consumed by individuals on a daily basis.

Phosphorus is naturally present in food, such as milk, nuts and beef, and has no impact on the taste or smell of the drinking water. It has been estimated that the average person would need to drink more than 980 glasses of tap water to get the same amount of phosphorus that they would get from one glass of milk.

The use of orthophosphate will increase the level of phosphorus in the drinking water to a maximum of 1 mg/L. Phosphorus is found in high amounts in protein-rich foods such as milk products, meat, beans, lentils and nuts as well as grains, especially whole grains. Phosphorus is found in smaller amounts in vegetables and fruit. In its natural form, phosphorus is a mineral that is part of every cell in our bodies but found mainly in our bones and teeth. It works in conjunction with calcium and other nutrients to build healthy bones and teeth. Phosphorus also helps maintain normal acid/base balance, supports growth, and is involved with the storage and use of energy. The orthophosphate will be at a low concentration and will not cause any negative health effects. 

There could be temporary cloudy or discoloured water as a result of the Corrosion Control Program, during times of watermain maintenance flushing or a watermain break.  If you experience discoloured or cloudy water from your tap please run your cold water tap for 5 to 10 minutes.  If the water does not run clear, call 905-546-2489 to report.

Phosphorus is an essential nutrient. The Estimated Average Requirement (EAR) of phosphorus for adults is 580 mg per day. With the increase in phosphorus in drinking water to a maximum of 1 mg/L, an average adult who drinks 2 litres of drinking water a day will take in less than 1% of an adult’s estimated average requirement.

Dietary Reference Intakes (DRI) for Phosphorus by Age (mg/day)

Estimated Average Requirement these DRI values are used with groups while Recommend Daily Allowance (RDA) values (not listed) are used for individuals. Adequate Intake (derived when insufficient data available to set EAR). Tolerable Upper Intake Level - The UL represents total intake from food, water and supplements. Not determinable - This value is not determinable due to lack of data of adverse effects in this age group and concern regarding lack of ability to handle excess amounts.  Source of intake should only be from food to prevent high levels of intake.

Phosphorus content of common foods

Individuals suffering from Chronic Kidney Disease must be mindful of the amount of phosphorus consumed in their diet and are typically recommended a phosphorus restricted diet. The amount contributed by tap water, while very low compared to foods and other beverages may still need to be taken into account. Concerns you may have about the presence of orthophosphate in drinking water are important concerns to share with your doctors (Family Doctor and Nephrologist) as it may influence the dietary restrictions, medication dosages and dialysis parameters. 

In-home hemodialysis equipment pre-treats the water used for dialysis. The Thin Film Composite Membranes used in the Reverse Osmosis water treatment process of the in-home hemodialysis equipment will successfully remove (reject) 96-98% of the orthophosphate in the water. In-home hemodialysis in Hamilton is coordinated through St. Joseph’s Healthcare Hamilton, Independent Home Dialysis Programs. Please consult your hospital program for questions pertaining to the In-home hemodialysis equipment; any clinical questions should be directed to your Nephrologist.

Copper and plastic are commonly used today for water pipes.  Before copper, lead and galvanized water pipes were common building materials used for water lines that connected to the City’s water distribution system.  Lead water pipes were installed from the house to the water main until 1955. Lead-based solders comprised of 50:50 lead/tin were used up until the late 1980s in Canada. Since 1990, the Canadian National Plumbing Code has restricted the use of lead solder in new plumbing and in repairs to plumbing for drinking water supplies.  Lead can also be found in brass faucets, fittings and valves.  Lead can be added to drinking water just from passing through or coming in contact with these lead pipes, fixtures, valves and lead solder.  The longer water sits in plumbing that contains lead, the more lead will dissolve and expose people to lead in tap water.  Lead sources and lead levels vary between buildings, so it is important to identify and remove any lead sources in each household. 

The maintenance, repair or replacement of the portion of the water pipe on private property is the exclusive responsibility of the homeowner.  Hamilton Water is authorized to repair or replace the portion of the water pipe on City property. 

It is estimated that there are 20,000 homes with lead water service pipes that are connected to the City’s water distribution system. 

If your home was built prior to 1955 you may have a lead water pipe.

Locate where your water pipe comes into your home. This is generally where your water meter is located, it may be in your basement, crawl space or fruit cellar. The section of pipe coming through the wall or floor is the pipe that you will look at to determine what your water service line is made of. Compare the pipe type to the chart below. This is the water pipe that extends from your house to the water main in the street. This pipe is also called your water service line; it connects you to the City’s water distribution system.  

If you are still unsure of your water service type, call 905-546-2489 and request a free Check Size and Type Inspection of your water service line.  

The best way to permanently reduce lead in your tap water is to replace any sources of lead in your plumbing system including your lead water service pipe.  The City is taking steps to reduce the amount of lead in your water by introducing the Corrosion Control Program (CCP). The CCP works by creating a protective barrier between any lead and the water; however certain activities such as construction or plumbing work can temporarily disturb this protective barrier which could result in short term lead exposure.  It is always best to remove the source of lead.

Sewer use
The City of Hamilton’s Sewer Use By-Law limits the phosphorus that can be discharged into the sanitary sewer at 10 mg/L.  With orthophosphate in the drinking water, some sewer users may be impacted and may need to obtain or amend their Overstrength Discharge Permit.

The concentration of orthophosphate targeted to be at 2.1 milligrams per litre, with operational adjustments possible between 1.8mg/L and 3mg/L. It has been estimated that adding up to 3 mg/L of phosphoric acid will increase the concentration of total phosphorus in the raw wastewater by about 0.3 to 0.6 mg/L or 4 percent. When the addition is reduced to the maintenance dose, which may be as low as 1-2 mg/L, the contribution to the wastewater influent will be reduced. 

Production or treatment
Some industrial and commercial users rely on the current water quality for production. Other companies need to provide additional treatment for their production needs. Adding phosphate to the drinking water may have an impact on production or treatment. It is recommended that companies contact their process consultants to confirm.

Cooling towers
The addition of orthophosphate may change the type and amount of precipitate that deposits and insulates commercial heat exchangers. As a result, companies may need to decrease their number of operating cycles, or alter their chemical treatment. It is recommended that companies contact their heating and cooling supplier or process consultant to discuss whether slight modifications are needed. 

Steam boilers
Many customers already add phosphate to precipitate calcium and/or as a tracer in their boiler system. Having orthophosphate in the drinking water will increase phosphate levels in the boiler feed and boiler water. For this reason, customers already adding phosphate to precipitate calcium may benefit from the implementation of corrosion control. These customers should measure their background phosphate levels and adjust their own phosphate dosage accordingly. Customers currently using phosphate as a tracer may need to find an alternative.