How to Treat the Water in a Cistern
If you have a cistern or are considering building one, you know that collecting rainwater can be a clean, inexpensive and reliable way to keep usable, potable water on your property, ready for your family to use. It is critical, however, that cistern owners maintain a clean system to prevent the growth of contaminants such as algae and bacteria that can cause illness.
Check your cistern regularly to make sure all filters and the access hatch cover are securely in place. Water management experts recommend having the tank professionally emptied and cleaned once a year. While the tank is empty, have it inspected for any cracks that might let in contaminants such as metals or bacteria from the ground. Have any cracks sealed. Do not try to do this yourself without safety equipment.
Disinfect the cistern using 5 oz. unscented household bleach for every 1000 gallons of water in the tank. Make sure you can still smell a tinge of bleach 30 minutes after treatment. If not, add another 1 oz. bleach.
Maintain a regular schedule, disinfecting the cistern every four months.