Water Treatment and Facilities

Metro Vancouver treats your drinking water in two stages. First it is treated at the source, at one of Metro Vancouver’s two water treatment facilities. It is given additional (secondary) treatment as it travels throughout the region. This ensures that your water remains high quality, even if you live far away from the original source.

Filtration and UV treatment at the Seymour Capilano Filtration Plant

The Seymour Capilano Filtration Plant is the largest drinking water filtration plant in Canada. Operating since 2009, it can treat up to 1.8 billion litres per day.

Water from both the Capilano and Seymour Reservoirs is treated at the Seymour Capilano Filtration Plant.

How does one plant treat water from two sources?

Underground tunnels transport water over 7 km from the Capilano Reservoir, so that water from both Seymour and Capilano can be treated at one facility.

The main drinking water treatment processes at the Seymour Capilano Filtration Plant are filtration and ultraviolet (UV) light. Filtration improves drinking water by removing particulates, organic matter, and micro-organisms. An added benefit of filtration is that less chlorine is required to maintain water quality in the distribution system. UV light inactivates any micro-organisms present in the source water.

Ozone and UV treatment at the Coquitlam Water Treatment Plant

The Coquitlam Water Treatment Plant is located north of the City of Coquitlam. It treats about 380 million litres of drinking water each day. The main drinking water treatment processes are ozonation and UV light.

Why does this treatment plant use ozone and UV, when the Seymour Capilano Filtration Plant uses filtration and UV? Each plant is designed specifically to treat the water it receives. The Seymour and Capilano watersheds are steep and during heavy rain soil is washed into the reservoir (erosion). Filtration is the most effective treatment process to remove these particles. The Coquitlam Watershed is of different geology and the water is more clear even during heavy rain events – ozone and UV provide excellent water treatment for this source.

There are natural particles and microorganisms in any water source. Even at low levels Metro Vancouver manages for these risks using a combination of ozone and UV light and chlorine to inactivate any micro-organisms present in the source water.

Treatment through the system

As water flows through the distribution system, the chlorine added during the primary treatment stage gradually breaks down, creating the potential for bacteria. If required, chlorine is added as a secondary disinfectant to preserve water quality as water travels to homes, businesses, and industries. Secondary treatment ensures water continues to meet Health Canada's standards as it travels through water mains across the region.

Corrosion control program: copper pipes protection

Our region’s drinking water originates from rainfall and snowmelt and is naturally acidic, which accelerates the corrosion of copper pipes and plumbing fixtures. To address this issue, Metro Vancouver first implemented the Corrosion Control Program in the 1990s, and has been adjusting its water treatment process over the years to protect copper pipes and hot water tanks across the region.

The most recent change happened in June 2021, when Metro Vancouver further increased the pH and alkalinity using natural minerals to make the water less corrosive. This was an important step in this long-term program, and since then, Metro Vancouver has been monitoring the water quality through enhanced sampling and testing to analyze the changes across the regional water system and assess the effectiveness of the pH and alkalinity changes.