What’s in a name? Rainwater or Rain Water?
What about Rain Harvesting, Rain Collection, or Rain Catchment?
According to the Merriam-Webster dictionary, Rainwater is correct, but it all means the same thing. Simply put, rainwater or rain water is water that falls from the sky.
What about the act of capturing the rainwater?
For our interests, we care more about the collection of the water. There are several variations in how people say that as well. Some say rain collection, some say rain harvesting, and others say rain catchment? Is it a regional thing? I know my northern cousins called soda “pop”. I don’t think I ever knew a southerner who called it that. Again, these terms all mean the same thing.
Rain Collection, Rain Harvesting and Rain Catchment are all just the means of capturing and storing rainwater.
Once you capture the water, how is it stored?
Now we can discuss the types of containers in which the water is stored. Here is where some differences can arise.
In ancient civilizations, cisterns were underground storage systems built to capture rain water and water flowing from aqueducts. The word cistern usually means an underground storage tank, but it is often used today to refer to above ground tanks of various types. In the Texas Hill Country, underground cisterns aren’t common because of the amount of rock just beneath the topsoil. Digging down to bury a cistern would be cost prohibitive. However, old swimming pools that are no longer being used can be converted to cisterns.
Then there are tanks. These are the most common containers used for storing rainwater, and they are made using a variety of materials.
Polyethylene, also known as Poly Tanks, are the most economical and range in size from 54 gallons to 5,000 gallons.
The larger tanks are shipped out on a flatbed trailer and require more room for delivery. Setup is fairly easy because the tanks can be rolled off the trailer and rolled to the pad, then pushed over and turned for final positioning. They need to be installed on a level pad, constructed from compacted gravel, sand, or concrete.
These poly tanks come in a variety of colors, but black and dark green are the best at preventing the growth of algae because they prevent UV light from entering the tank. They are made with food grade, BPA free polyethylene, and are suitable for potable water storage.
Since the maximum size is 5000 gallons, these tanks can be installed in series to expand the total capacity. You are only limited by the space you have.
Poly tanks are also used for bulk water storage for people who have wells. If your well pump goes out, it’s good to have a water holding tank with several hundred or thousand gallons on hand!
If you are on a tight budget but are devoted to rain harvesting or any bulk water storage, these are a great option.
Fiberglass tanks are the next most economical option. These tanks range in size from 50 gallons to 15,000 gallons and can be painted with any latex house paint.
Fiberglass tanks are extremely strong and not easily affected by heat and cold or direct sunlight exposure. They are heavier than Poly tanks, but lighter than steel tanks. They are a great option for rain collection.
As for installation, they can require a large area for transporting the tank and offloading from the trailer. They need a level pad, constructed from concrete or small compacted gravel.
Steel Tanks come in the largest variety of sizes. They can be as small as 90 gallons (one piece units), or as large as several hundred thousand gallons (assembled onsite). The multi-ring tanks are assembled at the site, so they are much easier to get into a tight space. They also require a level pad of concrete or a rock base with a layer of sand on top. These tanks are constructed using curved, galvanized sheet metal pieces which are bolted together to form rings. Once the sides are assembled and the roof is attached, the polyethylene liner is attached to the inside. Since the liner sits directly on the ground, it is critical that the base of the pad is soft (sand) and has no sharp objects that could pierce the liner. It is also critical that sand and rock are packed against the outside bottom rim of the tank so as to keep the liner from sneaking under the sharp edges of the bottom rings and getting cut.
The tank in these pictures is an 18,800 gallon rain catchment tank with a 30 degree sloped roof. Certain sizes are also available with a 10 degree pitched roof, and there’s also a flat roof (slight dome shape) option.
While steel tanks are the most expensive option, they are also the most aesthetically pleasing from a design perspective. Architects love them because they compliment many modern home designs.
No matter how you slice it, harvesting, collection, or catchment of rainwater or rain water is all the same. You can count on having the best quality water on hand to supply your entire home, or keep your gardens happy.