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Water Safety

Cleaning a cistern

​​​​​​​​​​​Once you fix the contamination problem, you need to clean and then disinfect the cistern. Before you start, arrange for the services of an approved water hauler—you need clean, safe water to clean and disinfect a cistern.

When do I need to clean my cistern?

You need to clean the cistern to remove sediment and other contaminants. It’s a good idea to clean your cistern at the following times:

  • at least 1 time a year to remove sludge and sediment buildup
  • when the water looks, smells, or tastes different than usual, and a test tells you it’s contaminated
  • when contaminants—such as rodents or water from overland flooding—get in the cistern
  • after the cistern is installed and sediment needs to be removed from the bottom of the tank

How do I clean my cistern?

Follow these steps to clean your cistern:

  1. Learn about confined-space entry precautions and follow them.
  2. Make sure your footwear and equipment are clean before​ you go into the cistern.
  3. Drain the cistern completely. Don’t use a sewage hauler to pump out the cistern.
  4. Wash all inside surfaces of the cistern. Use a pressure washer or a stiff brush and a non-corrosive, non-foaming, food-grade detergent to loosen debris and sediment. Use a wet-dry vacuum to remove sludge on the bottom, if needed.
  5. Rinse the cistern with clean water that’s safe to drink, and then drain the water to waste.

After it’s clean and rinsed, the cistern is ready to disinfect.

Current as of: May 25, 2022

Author: Environmental Public Health, Alberta Health Services