When considering water tank sizes there are several things you need to keep in mind. These factors should form the crux of your tank buying decision making process at any given time.
How much rainfall do you get in your area in a typical year? If you get a lot of rain then it is advisable for you to purchase a large water tank. On the other hand, you will be surprised how much rainfall you can collect from the roof of an average sized house, even in a dry area. It is probably advisable to get a tank of a couple of thousand litres to supplement a househol’ds water use in an urban area.
• Roof Area
A large roof surface will definitely collect more water than a small roof surface. Thus you should keep this in mind when selecting your tank size. If you have a big collection surface, you can go for a larger tank. Those with a relatively small collecting surface can purchase tanks that are average in size.
• Water Usage
You need to be aware of the water usage in and around your home. If your home relies heavily on water then you have to factor it in when looking for the right water tank size for you. The more water you use the bigger the size of the tank you are supposed to get. If you are expecting to have water left in the tank for use during the rainy season then you need to keep this in mind too.
• Site characteristics
You also need to look at the space you have for the tank. If you do not live in a place that has enough space it will be difficult for you to find space for a big tank. Howveer in this case you could consider a poly or concrete underground tank.
For some simple calculations that will come in handy when you are making this decision this is what you need to do. Firstly, get the Area of your Roof (in m2) and multiply it by the annual rainfall for your locality. This should be able to give you the maximum you can capture in a rainy season. After this, you will need to calculate the storage volume you should have at the beginning of a dry season. For this, you will need to know how many days one can go without rain in your area. When you have this, multiply it by the average litres of water you use on a daily basis in your household. This should give you the storage volume you should have in the tank at the beginning of any dry spell.
So for example, if a dry season lasts for 90 days, and your family uses 600 litres of water daily, then you will need to have a tank that will contain at least 54,000 litres of water at the start of a dry patch. This method is not set in stone, there is every possibility of the tank not being full at the start of the dry patch but this should serve as a guide to you when looking for the right water tank size for you. Of course, you can always ask for help from the tank shop if you can’t find your way around this.