How to plan for your Rainwater Catchment System
Trying to figure out what you need and what size tank is right can be a bit overwhelming. This page will hopefully help guide your journey to owning your own rainwater cistern and complete collection system.
Usage
One of the first question you should ask yourself is what exactly will I be using rainwater for? and how frequently will I need it? Let's look at 2 scenarios:
A.) I have a few planters on my patio that I like to water with rainwater, and I also have a small garden bed where I grow a few vegetables.
B.) I want to irrigate half an acre of farmland. I would also like rainwater for my barn animals and maybe to wash my car.
Both these scenarios use rainwater, but one may require a smaller quantity of water to maintain, while the other will require a whole lot more. So, from this you should start thinking of all the ways you may need or potentially want to utilize rainwater. Generally, the more you want/need to use, the bigger the tank capacity should be.
Rain Frequency.
Consider the climate in your area. You may live in an area where you get little to no rain; or you may get a lot of rain during a certain part of the year, but not so much all year round. If your area experiences droughts or just not enough rainwater, then its best to try and capture as much as possible when it rains. This year in Texas we have received some record heat and some harsh stints with no rain. The rain has been unpredictable here, having a larger tank size when not knowing when the next rain will be is worthwhile investment for keeping your plants alive!
Roof size and space for a tank. These two factors are the most important to consider. Let us look at roof size. a 1,000 Square Foot Roof can capture 623 gallons (about 2358.31 L) of water in only a 1 inch of rain. The average home has about a 3,000 square ft (about the area of a tennis court) roof. The average rainfall is in the US is 30.21 inches. Without doing the math you can see that is a lot of rain hitting your roof, running away when it could be captured! Overall, the bigger your roof the more rainwater you can potentially catch.
Now that we know we can get a lot of rainwater off the roof, we must consider where we will put the tank. Now this isn't a one size fits all situation. Each home is different and how you use your space can be completely different from the next home. To decide what size works for you, you'll have to measure the potential space in your yard that is available to place a tank upon. This is where it can get tricky. If you only have so much room, then getting a large tank may not be the best possibility. Also, height plays a factor, your tank should not be taller than the eve of your roof.
