How to Determine what Size Water Cistern Tank You Need

What You'll Need
Old water bill
Graph paper and pencil

A cistern tank is a structure that is used to collect water. They have been around for centuries, but today many people use them to collect rain and run off water for garden or emergency purposes. In some rural areas, they are still used in places where a well isn't an option. It's also not uncommon to see them in desert areas where water is a precious commodity. There are plenty of reasons you may want to use one now. Here are a few tips to help you determine the size tank you need if you are going to create one.

Step 1: Determine Your Needs

If you are only wanting to use a tank to collect excess water for gardening, a large tank won't be necessary. If you are wanting a cistern for emergency uses, then a tank large enough to supply your household needs for a few days will be necessary. To determine what size tank you need, you first have to figure out what its use will be.

Step 2: Calculate Your Water Consumption

To have a cistern as a back up supply you will need to find out how much water you generally consume in an average day. There are a few methods to do this. The easiest way is to simply look at a water bill. Take the number of gallons used over a month and divide it by 30. This will give you an idea of how many gallons of water you use a day. 

Step 3: Location 

Another thing to consider is where you are placing your cistern. A loft or attic cistern is generally going to be no larger than 25-55 gallons for space concerns. On the other hand, a cistern that is placed outdoors in a field can take as much as 2400 gallons. While a tank this size isn't going to be necessary for most people, it can be used to give back up water to a community. A cistern used to collect run off water only needs to be a few gallons.

Step 4: Set Up

A cistern can be connected to your current water supply to use for emergencies. It can also be used to save on your water consumption. Connecting a cistern to your existing pipe lines will require some extra work, and this will also help determine the size you need. Many people use cisterns to save money on their cold water use. Hooking a cistern up in this manner will require you to store the cistern near the pipes. This means the tank can be no larger than the space you have dedicated for cold water storage.

Step 5: Plan It Out

The best way to ensure you are going to use the right size tank is to draw a plan. A scaled plan will help you determine the best size tank for the location you have chosen.