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Recommendations for reopening building water supply systems

Building owners and operators need to prepare in advance

Use our reopening recommendations to safely re-open your building’s hot and cold water supply following a long term shut down.

How building closures can affect water quality

Serious problems can happen when water pipes in a closed building are not maintained or routinely flushed.

Stagnant water in the building’s pipes, equipment and water storage tanks can cause building plumbing issues and concerns with water quality and water appearance.

It can also increase potential adverse effects or health risks such as:

Reopening recommendations

In Peel, Peel Region is responsible for supplying clean, safe drinking water to each property.

As a building owner or operator, you are responsible for maintaining the safe water supply from your property line to and within your building*. You are also responsible for protecting the health of those who use your building’s water.

*The information the link refers to is homeowner’s responsibilities for their private side pipes. This information applies to all private side pipes both residential and business.

Begin by reviewing your water management plan

Before taking any action, review your existing water management plan and a sketch of the entire building and property.

Flushing the entire system

After months of inactivity, the building plumbing must be flushed (by opening taps and equipment) to move the stagnant water out. We also recommend cleaning all taps, devices and fixtures.

Staff must wear appropriate personal protective equipment such as gloves, a mask and eye coverings while flushing the system.

If your building is large, perform the required water testing for large buildings after the pipes are flushed to confirm water safety and quality.

Flush your cold-water supply first before flushing hot water taps.

Water supply system flushing instructions

Flushing conditions will vary based on your building’s piping configuration and size.

Hot water


Shock chlorination

If water system shocking is necessary, it should be conducted by a qualified water treatment professional.

You may need shock chlorination if you have a large system that:

Water testing for small buildings

If your building is small, the water should be consistently cold and have a mild smell of chlorine.

Water testing for larger buildings

If your building is largeor serving vulnerable populations, we highly recommend water testing.

Testing for chlorine residual should be performed by a qualified person using appropriate and calibrated testing equipment.

Testing for microbial parameters should be carried out by an accredited laboratory for a building or facility that is:

More information on opening water supply systems

This guidance is meant to give simple step-by-step instructions for safely reopening a building’s water supply system.

For more detailed information, review the Ontario Guide for maintaining building plumbing after extended vacancy or Canadian Water and Wastewater Association guidance documents.

Peel Region continuously monitors the water quality of its municipal drinking water supplies. To learn more about how we test and treat water in Peel, read our water and wastewater quality reports.

Contact us

If you have a specific question about water quality in Peel, email the Peel Region Water Quality and Compliance department.

For guidance on water testing in private buildings, call Peel Public Health at 905-799-7700.