A cistern needs to be disinfected every time it gets cleaned.
Your cistern needs to be disinfected without cleaning at the following times:
The amount of disinfectant you need depends on how much water the cistern holds. If you don’t have this information, you can estimate using the calculations below.
Box cisternTo estimate how much water your box cistern can hold, you’ll need a calculator and the following measurements in metres:
Take these measurements and multiply them by each other: L x W x H. Then multiply the result by 1,000. The answer will tell you how many litres of water your cistern can hold, so you can figure out how much disinfectant to use.
If a box cistern is 2.5 metres long, 1.5 metres high, and 1.7 metres wide, do the calculation like this:
2.5 x 1.5 x 1.7 = 6.38 metres3
6.38 x 1000 =
6380 litres (amount of water the cistern holds)
Cylindrical cisternTo estimate how much water your cylindrical cistern can hold, you’ll need a calculator and the following measurements in metres:
Take the measurements and follow these steps:
The answer will tell you how many litres of water your cistern can hold, so you can figure out how much disinfectant to use.
If your cylindrical cistern has a radius of 1.1 metres and is 1.8 metres high, do the calculation like this:
Step 1: 1.1 x 1.1 = 1.21
Step 2: 1.21 x 3.14 = 3.8
Step 3: 3.8 x 1.8 = 6.84
Step 4: 6.84 x 1000 =
6840 litres (amount of water the cistern holds)
When you’re ready to disinfect your cistern, bypass all water treatment devices and turn off the water heater. Then follow these steps:
If there are bacteria in the water sample, you need to find the source of contamination and fix the problem. Then you need to clean and disinfect the cistern again. If there are no bacteria in the next sample, the water is safe to drink.
Current as of: May 25, 2022
Author: Environmental Public Health, Alberta Health Services
This material is not a substitute for the advice of a qualified health professional. This material is intended for general information only and is provided on an "as is", "where is" basis. Although reasonable efforts were made to confirm the accuracy of the information, Alberta Health Services does not make any representation or warranty, express, implied or statutory, as to the accuracy, reliability, completeness, applicability or fitness for a particular purpose of such information. Alberta Health Services expressly disclaims all liability for the use of these materials, and for any claims, actions, demands or suits arising from such use.