How Urban Growth Is Increasing Pressure on Local Water and Sewer Systems
Canada’s cities and communities are changing quickly. New subdivisions are expanding beyond established neighbourhoods, condominium developments are increasing density, and areas that once had relatively modest populations are accommodating thousands of additional residents. Growth brings new homes, businesses, jobs, and opportunities, but it also creates challenges that are much less visible from the street.
One of the biggest is what happens underground.
Every new home requires reliable access to drinking water and a way to move wastewater safely to treatment facilities. More residents mean more showers, toilets, washing machines, dishwashers, sinks, and other fixtures drawing water and sending wastewater into municipal systems. At the same time, expanding paved areas can increase the amount of stormwater that needs to be managed.
Canada’s first National Infrastructure Assessment identified population growth, housing pressures, demographic changes, and increasing climate risks as factors putting greater strain on infrastructure. Water and wastewater systems are among the essential services communities need to support continued housing growth.
The challenge is not simply building enough homes. Communities also need the underground infrastructure capable of supporting them for decades to come.
More People Mean More Demand for Water
The relationship between population growth and water infrastructure is straightforward: as communities grow, the number of people relying on the system increases.
Municipal water systems must collect or obtain water, treat it to drinking-water standards, store it, and distribute it through networks of water mains and smaller pipes. Pumps, reservoirs, treatment facilities, valves, and other equipment all contribute to keeping that system functioning.
Adding thousands of homes can substantially increase demand across that network.
Growth does not necessarily mean that communities will run out of water. Water-efficient fixtures, conservation efforts, improved infrastructure, and better system management can help communities serve larger populations more efficiently. However, municipalities still have to ensure that treatment and distribution capacity keeps pace with development.
This requires long-term planning rather than simply connecting one development after another to existing infrastructure.
The same issue exists on the other side of the plumbing system.
Wastewater Has to Go Somewhere
Water entering a home eventually leaves it.
When someone takes a shower, flushes a toilet, runs a washing machine, or uses a kitchen sink, wastewater enters the drainage system and is eventually carried toward municipal wastewater infrastructure in serviced communities.
At the national level, the scale is enormous. Statistics Canada reports that almost 32.9 million people were served by municipal wastewater systems in 2024.
Environment and Climate Change Canada notes that millions of cubic metres of wastewater from homes, businesses, institutions, and industries enter municipal sewer systems every day. Municipal wastewater is also one of Canada’s largest sources of pollution to surface water, making effective treatment essential before wastewater is released back into the environment.
As communities become larger and denser, sewer networks and treatment facilities therefore have to accommodate greater volumes.
A system that was adequate when a neighbourhood was first developed may face very different demands decades later.
New Development Often Relies on Older Infrastructure
One of the more complicated aspects of urban growth is that new and old infrastructure frequently have to work together.
A newly constructed subdivision might contain modern pipes and drainage systems, but those systems can eventually connect to infrastructure serving older parts of a municipality. Similarly, redevelopment can add considerably more people to an established area without rebuilding every water main and sewer beneath surrounding streets.
Imagine an older property being replaced with a multi-unit residential development. The amount of land occupied might barely change, but the number of residents using water and producing wastewater can increase substantially.
Multiply that pattern across an entire community and the cumulative demand becomes significant.
This is one reason infrastructure planning must consider future development rather than only current usage.
It is also important because some existing Canadian wastewater infrastructure has already been in service for decades. The Canadian Infrastructure Report Card notes that a large portion of linear wastewater infrastructure is more than 50 years old and that about 15% of these assets have an unknown condition.
Growth and infrastructure renewal therefore often need to happen simultaneously.
Urban Growth Changes How Rainwater Moves
Population growth affects more than drinking water and sanitary sewers.
Development changes the landscape itself.
Natural areas can absorb significant amounts of rainfall. Soil, vegetation, wetlands, and other permeable surfaces allow water to infiltrate the ground or temporarily store it.
Urban development introduces more roofs, roads, parking lots, sidewalks, driveways, and other hard surfaces. Instead of soaking naturally into the ground, more rainfall can become surface runoff.
That water has to go somewhere.
Modern developments typically incorporate stormwater management into their design, but rapid urban expansion can still create challenges across the broader drainage network. Heavy rain falling over a highly developed area can produce large volumes of runoff over a relatively short period.
That makes stormwater management an important part of sustainable urban growth.
Climate Conditions Add Another Layer of Pressure
Infrastructure planners are not preparing only for larger populations. They must also consider changing environmental conditions.
Extreme precipitation is particularly important because drainage infrastructure has traditionally been designed using historical rainfall information. As rainfall patterns change, infrastructure designed around past conditions may not always represent the level of resilience communities will require in the future.
For municipalities, this creates a difficult planning challenge.
Water and sewer infrastructure is expected to remain in service for many decades. Decisions made today therefore have to account for conditions well into the future.
The problem becomes especially complicated when population growth and severe weather occur together. A community may simultaneously experience more residents using sanitary infrastructure and more intense rainfall, placing pressure on stormwater systems.
Building resilience means considering both.
What Happens When Systems Become Overloaded?
The consequences depend on the type of infrastructure and the nature of the problem.
Heavy rainfall can overwhelm drainage capacity in some circumstances, contributing to localized flooding or sewer backups. In systems where stormwater and wastewater interact, excessive flows can also increase pressure on treatment and collection infrastructure.
Wastewater problems have environmental consequences as well.
Municipal wastewater needs to be properly treated because insufficiently treated wastewater can affect rivers, lakes, and other surface waters.
For homeowners, infrastructure problems may become visible in much smaller ways first.
Slow drainage, recurring backups, unusual plumbing behaviour, water-pressure changes, or problems affecting several fixtures can sometimes indicate that something beyond a single fixture requires attention.
Not every household plumbing problem is caused by municipal infrastructure. In fact, many originate entirely within the property. That distinction is important.
When problems repeatedly occur inside a home, trained and experienced plumbers can assess the property’s plumbing and determine whether the likely cause is within the building, the private sewer connection, or something that may require attention from the appropriate utility or municipality.
That diagnosis can prevent homeowners from repeatedly treating symptoms without addressing the actual source.
Aging Pipes Make Growth More Complicated
Underground infrastructure does not last forever.
Pipes can deteriorate, joints can fail, roots can enter damaged sewer lines, and changing soil conditions can affect buried infrastructure. Different pipe materials also have different expected service lives.
The Canadian Infrastructure Report Card estimates that sewers can have expected service lives of roughly 70 to 100 years depending on their material. It also reports that while much of Canada’s wastewater infrastructure is considered to be in good or very good condition, portions are rated fair, poor, or very poor.
This means municipalities have to balance two expensive responsibilities: expanding infrastructure for future development while renewing infrastructure that already exists.
Ignoring either side creates problems.
Building new neighbourhoods without sufficient supporting infrastructure can create capacity concerns. Focusing entirely on expansion while postponing renewal can allow existing assets to deteriorate.
Sustainable growth requires both.
Water Infrastructure Is Part of Housing Infrastructure
Water and sewer systems are sometimes discussed separately from Canada’s housing challenges, but the two are closely connected.
Homes cannot simply be built wherever land is available. They need roads, electricity, water, wastewater capacity, stormwater management, and other essential services.
Canada’s National Infrastructure Assessment explicitly identifies water and wastewater infrastructure as housing-enabling infrastructure.
This changes how we should think about urban development.
A housing project is not only a collection of buildings. Every new development becomes part of a much larger network of public infrastructure.
The pipes beneath a community can ultimately influence how quickly and sustainably that community is able to grow.
Better Planning Can Reduce Future Pressure
There is no single solution to infrastructure pressure.
Increasing the size of every sewer or water main would be enormously expensive and, in many situations, unnecessary. Instead, communities can combine infrastructure expansion with better monitoring, strategic replacement, conservation, stormwater management, and smarter development planning.
Municipalities can identify areas where capacity improvements are required before major development occurs. Aging assets can be prioritized based on condition and risk rather than waiting for failures. New developments can incorporate effective stormwater management from the beginning.
Households also have a smaller but meaningful role.
Repairing leaks, maintaining private plumbing and sewer connections, avoiding inappropriate materials being put down drains, and using water efficiently all contribute to better system performance.
None of these measures replaces the need for adequate municipal infrastructure. However, reducing unnecessary demand and preventing avoidable plumbing problems helps existing systems operate more efficiently.
Green Infrastructure Can Work Alongside Traditional Systems
Urban growth does not have to mean directing every drop of rainfall immediately into underground pipes.
Green infrastructure provides another approach.
Rain gardens, permeable surfaces, vegetation, trees, bioswales, green roofs, and other measures can help capture or slow stormwater before it enters drainage systems. Instead of treating rain as something that must immediately be transported away, these approaches attempt to manage some of it where it falls.
They are not replacements for sewers, treatment plants, or conventional stormwater infrastructure. Rather, they can complement those systems.
This becomes increasingly valuable as communities become denser. Preserving or creating areas capable of absorbing water can help offset some of the hydrological changes associated with additional buildings and pavement.
The result can also be greener and more comfortable neighbourhoods.
Infrastructure Decisions Made Today Will Last for Generations
Perhaps the most important consideration is the lifespan of what is being built.
A new subdivision may be completed within a few years, but the infrastructure supporting it could remain underground for generations. Decisions about pipe capacity, materials, drainage, treatment capacity, and future expansion therefore have consequences far beyond today’s housing demand.
Canada is continuing to urbanize. Statistics Canada found that 18 of the country’s 25 largest municipalities grew faster than the national population growth rate between 2016 and 2021, illustrating the continuing concentration of growth in urban areas.
The question is therefore not whether growing communities will place additional demands on infrastructure. They will.
The more important question is whether infrastructure can evolve alongside them.
Building Communities That Can Handle Growth
Urban growth is often measured by visible changes: new houses, taller buildings, expanded roads, new businesses, and growing neighbourhoods.
Yet some of the most important infrastructure remains invisible.
Water mains deliver clean water every day. Sewer networks carry wastewater away from millions of Canadian homes. Stormwater systems help communities manage rainfall. Treatment facilities help ensure wastewater can be safely returned to the environment.
As communities grow, all of these systems must grow, adapt, or operate more efficiently.
That requires investment, careful planning, responsible household water use, infrastructure renewal, and development strategies that consider what is happening both above and below ground.
Canada needs more housing and communities capable of accommodating future growth. But sustainable urban growth involves more than constructing additional buildings. It means ensuring that the essential systems underneath those buildings remain reliable for the people living there today and for the generations who will rely on them tomorrow.
