Corrosion Control

The Ontario Ministry of the Environment and Climate Change (MOECC) Drinking Water Systems Regulation (O.Reg. 170/03), 2007 requires all municipalities in Ontario to test for lead in their distribution system as well as the lead levels out of customers’ faucets.  Lead can be released when drinking water comes in contact with lead pipes, lead-based plumbing fixtures and lead solder.

There are an estimated 20,000 homes with lead water pipes in Hamilton. You cannot see lead in drinking water and it has no taste or smell.  Lead can cause serious health problems. Infants, young children and pregnant women have the greatest risk of negative health effects from lead exposure.

The City’s Lead Sampling Program (PDF, 414 KB) confirmed that more than 10 percent of lead samples taken from residential plumbing systems with lead water pipes exceeded 10 micrograms of lead per litre (μg/L). As a result, the MOECC required the City of Hamilton to develop a Corrosion Control Plan. There are 20 communities in Ontario required by the MOECC to develop and implement a Corrosion Control Program to reduce the amount of lead in tap water.

Why is the City of Hamilton implementing a Corrosion Control Program?

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 and Climate Change (MOECC) 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 of 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 film is created inside the pipes that reduce 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.

The City has proposed having orthophosphate, a phosphate-based inhibitor in the drinking water process to protect residents from the release of lead into drinking water. 

What is orthophosphate?

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 film on plumbing surfaces that reduces the release of metals, such as lead and copper from household plumbing.

Are there other communities that use orthophosphate in their drinking water?

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.

The following Canadian cities treat their water with phosphates:

  • Toronto
  • Winnipeg
  • Sudbury
  • St. Foy
  • Dartmouth
  • Bathurst
  • Campbellton

The following United States cities treat their water with phosphates:

  • Washington D.C.
  • New York City
  • Detroit
  • Chicago
  • Atlanta
  • Nashville  

When will orthophosphate be present in the drinking water?

Orthophosphate is expected to be present in the drinking water system in 2018/2019.  The changes will be made at the Woodward Water Treatment Plant that provides water to most of the City of Hamilton.  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 and Climate Change (MOECC) threshold. Therefore they do not require a Corrosion Control Program.

Lynden has experienced historical issues related to the intermittent release of lead within this system and as a result the Drinking Water Advisory remains in place. The occasional release of lead into the drinking water in Lynden is not related to corrosion. It is due to the presence of lead in low concentrations within the source water.    

How much orthophosphate will be present in the water?

During implementation, the concentration will be three milligrams per litre (3 mg/L).  Hamilton Water will monitor and adjust water treatment operations to ensure lead concentrations are below the Maximum Allowable Concentration (MAC) of 10 mcg/L.  We expect the concentration to maintain the protective coating after implementation to drop to approximately 1 to 2 mg/L.  

Has the City test this approach?

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.  

How will the City know that corrosion control is working?

The City will develop 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

Will you monitor the impact of the corrosion control on the environment?

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. 

What are the costs for corrosion control?

The construction cost to implement corrosion control at the Woodward Water Treatment Plant is expected to be $4.95 million and the annual operating cost is estimated at $310,000. 

How does lead affect your health?

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

How does orthophosphate reduce lead in drinking water?

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.

Is it safe to have orthophosphate in 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 overall, would be only one source of phosphate consumed by individuals on a daily basis.

Phosphates are naturally present in food, such as milk, nuts and beef, and have 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 330 glasses of tap water to get the same amount of phosphate that they would get from one glass of milk.

Are there any negative health impacts from drinking water with orthophosphate?

When orthophosphate is present in the drinking water the level of phosphorus in the drinking water will increase to a maximum of 3 mg/L.  Phosphorus is found in high amounts in protein-rich foods such as milk and milk products and meat and alternatives, such as beans, lentils and nuts.  Grains, especially whole grains, provide phosphorus.  Phosphorus is found in smaller amounts in vegetables and fruit. In its natural form, phosphorous 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.  

Could there be changes to the appearance of the water?

There could be temporary cloudy or discoloured water as a result of implementation 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 905-546-4426 to report.

How much phosophorus is recommended for optimal health?

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 3 mg/L, an average adult who drinks 2 litres of drinking water a day will take in 6 mg of phosphorus which is 1% of an adult’s estimated average requirement. For more detailed information please see the graphs below or read the Phosphorus Backgrounder (PDF, 178 KB).

Dietary Reference Intakes (DRI) for Phosphorus by Age

Age Estimated average requirement for males (mg/day) Estimated average requirement for females (mg/day) Tolerable upper intake level
0-6 months 100 100 Not determinable
7-12 months 275 275 Not determinable
1-3 years 380 380 3000
8 years 405 405 3000
9-18 years 1055 1055 4000
19-70 years 580 580 4000
Over 70 years 580 580 3000
Under 18 years, pregnant   1055 3500
19-50 years, pregnant   580 3500
Under 18 years, lactation   1055 4000
19-50 years, lactation   580 4000

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

Food / beverage Portion Phosphorus (mg)
Cheddar cheese 50 g 256
Milk, 1% 250 mL 272
Yogurt, plan, 1%-2% 175 mL 261
Salmon, pink, canned, drained with bones 75 g 274
Lean ground beef, pan fried 75 g 174
Almonds, roasted 60 mL 171
Baked beans with pork, canned 175 mL 202
Peanut butter, natural 30 mL 113
Instant oatmeal, plain 1 packet (186 g) 132
Bread, whole wheat 1 slice (35 g) 80
Peas, green, cooked 125 mL 100
Potato, baked, flesh and skin 1 (173 g) 121
Banana 1 (118 g) 26
Cola beverage 1 can (355 mL) 48
Milk chocolate bar 1 bar (50 g) 104

Do I need to take precautions if I have Chronic Kidney Disease?

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. 

I have in-home dialysis equipment; will orthophosphate affect it?

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.

How does lead get into drinking water?

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. 

Who is responsible for the water pipe?

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. 

How many homes in Hamilton have lead water pipes?

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

How do I know if I have a lead water pipe?

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 and it may be in the basement, crawl space or fruit cellar. Look for where the pipe comes through the wall or floor. 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. 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.  

Copper pipes


Copper pipes began to be the most common pipe used in the construction of new homes built from the 1960s to present. Copper plumbing is typically thin-walled, making it smaller in diameter than steel pipe. Copper is known for its durability, heat tolerance and long life span. One concern with copper, especially in homes built before 1990, is that the joints (where the pipes connect to various fittings) may contain lead-based solder. 

Over time, oxidation might change copper pipes from their original shiny reddish hue as seen here, to a dark brown or green like the next photo.

The pipe coming out of the floor is the water service line that extends out to the water main in the street.  In this image this pipe is made of copper. The copper is aged and has a darker brown patina and the section near the floor has a small area of green patina, which is very common. The blue handle on the pipe is the water shut-off valve for the home. From there the water flows through the water meter and then connects into the home’s internal plumbing.

Galvanized pipes


Galvanized or zinc-coated steel pipes appear thick and heavy with a grey or silver metallic exterior. Galvanized steel pipes are not commonly used in modern construction, but if your home was built from the 1930s to the 1980s, it's common to find galvanized pipes.

Since steel pipe is naturally heavy, it's more difficult to work with than other pipe materials, and although it's very durable, galvanized steel does have a limited lifespan. The zinc coating can eventually break down and cause the pipe to rust internally, which may lead to reduced water pressure and clogged water lines.

Water flowing through galvanized pipes may also have a metallic taste or contain high concentrations of iron or zinc.

A threaded galvanized pipe with elbow.

A cross section of galvanized pipe showing internal rust accumulation.

Lead pipes


Lead pipes are no longer used in residential plumbing, but lead was once the go-to material for connecting a home’s plumbing system to the city system. Unpainted lead pipes are a dull grey in colour and because they are soft when you gently tap them they will not echo like a galvanized or copper pipe. If you were to scrape the surface of the pipe gently the metal beneath would be shiny and silver. 

A lead pipe coming through the floor.

A lead pipe excavated from the ground during a lead service line replacement. The shiny silver and dull grey is lead. The brown on the outside of the pipe is dirt from the excavation.

What are the potential impacts for industrial and commercial users?

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.

Phosphoric acid will initially be added at a concentration of 3 mg/L of PO4 (phosphate). 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.