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Determining the Best Cistern for your Location

Wondering which cistern tank size will work best for your location? See a similar question asked by another customer, as well as the answer.


I need your help. Please can you give me more details on a cistern tank? I'm not sure what size I should have. For example, a 7 story building--what will be the size of cistern for water tank? Every floor has a toilet and the size of toilet is 3.5 X 6.0m.


Thank You for contacting the Portable Tanks, a division of GEI Works with your question. For our collapsible rainwater collection tank, there are several different sizes and options you could consider. In general, these pillow tanks can be made in almost any size ranging from 1 to 210,000 gallons. When used for rainwater collection, most fabrics used for the tanks will be FDA and NSF 61 approved.

Determining a Cistern Tank Size

In order to determine how big a cistern you may need, you will need to determine how may gallons all the equipment and devices in your 7 story building are uses. The size of the toilets will not necessarily be as important as knowing how much water is being flushed down them.

rainwater collapsible tankIn addition to thinking about toilets, you may also want to consider other sources of water that are being used within the building. These may include sinks, showers, hoses, and sprinklers.

One helpful tool we offer to customers looking to determine the amount of water they need to use is the Water Consumption Calculator. This calculator includes several different features to help walk you through how much water you may be using. Features commonly found on the calculator include:

  • Average Number of Daily Flushes Per Person
  • Number of People in the Building
  • Approximate Amount of Gallons per Flush

Once you determine how much water your building may be using on a daily basis, you can then work towards determining how much water may need to be storing inside your water cistern.

If you are planning to use this cistern purely as a rainwater collection unit, you may want to also consider your rainfall amounts as well as the amount of space you have available in your location. To view all information on these tanks including sizing, please check out the Cistern Tank Size Page.

For pricing information and discussion on a cistern tank size, please feel free to Request a Price Quote. Don't hesitate to contact our tech team for further questions at +1-772-646-0597.