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Flushing your facility's water system

When a building has been closed or operating at reduced capacity, water sitting in the pipes can create health and mechanical risks. Flushing your system before reopening helps ensure safe, clean water throughout your facility.

Why flushing matters

Stagnant water in an inactive building can lead to a range of mechanical and health problems. Common issues include:

  • Microbial or pathogen growth
  • Disinfection by-product build up in stagnant water
  • Pump failure
  • Pipe failure
  • Discoloured water (cold and hot)

Step 1: Develop your plan

Every facility is different. Before you start flushing, take time to map out your system and identify what needs attention. At minimum, your plan should cover:

1
Map your system
Identify critical valves, pumps, tanks and other equipment. Access or sketch your mechanical plans so you know where everything is before you start.
2
Check water service size and pipe dimensions
Larger services and waterlines require more flushing time. Measure what you have so you can plan accordingly.
3
Locate boilers and hot water tanks
Confirm hot water is being heated to a minimum of 60°C (140°F). Your facility may have multiple hot water sources.
4
Plan your flushing sequence
In multi-storey buildings, start at the lowest level and work up. In single-storey buildings, start closest to where water enters. Include food fixtures, such as coffee makers, ice machines and water dispensers.
5
Flag drains, traps, and sewage plumbing
Note the location of drains, backwater valves and pumps. These may need maintenance if they've been out of regular use.
6
Call in professionals where needed
Contact plumbers or contractors for anything you're not comfortable with — especially storage tanks, cooling towers or facilities serving vulnerable populations.

Step 2: Flush the lines

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Start slow. Plumbing and fixtures that have been idle may have leaks or other issues. Your plan and sketches will help you catch problems early.
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Expect discoloured water if the facility has been closed for a period of time. Document where and for how long discolouration occurs. This helps with future maintenance planning.
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Long pipe runs and dead ends need more flushing time than high-use areas.
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Your municipality maintains disinfection throughout the distribution system. Your facility flushing builds on that — it doesn't replace it.
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A sewer smell likely means a plumbing trap has dried out. Flushing nearby fixtures should resolve it.
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For hot water lines, start with the fixture closest to the hot water tank or boiler. If discolouration persists, consult the manufacturer's instructions.

Flushing a fixture doesn't replace cleaning it. Wipe down touch points and discharge locations as part of your reopening process.

Step 3: Document your work

Keep a log of your flushing activities: which fixtures were flushed, when, and whether any issues were found. Good records protect you if problems arise later and help plan future maintenance.

Additional technical resources

Have a question?

Contact Environmental Health