Each component and process of a whole-house rainwater harvesting system is critical. Rainwater storage is no exception. This is an in-depth look at the process of storing rainwater.
How is it possible to have clean rainwater in the storage tank, that appears to be left stagnant when not in use, without adding chemicals?
Let’s take a look.
Rainwater – Before rainwater falls to the ground, it goes through a purification process known as distillation, this will remove most particles and contaminants. As rainwater falls and lands on rooftops, some contaminants come in contact with the water, such as carbon dioxide in the air, pollen, and other organic matter, but never inorganic matter.
Rooftops are never used that introduce more contaminants into the water, and also the piping and storage that is used.
While it’s falling, rainwater is essentially the purest water that can be naturally found. These are the only contaminants that are introduced in the water and are firmly mitigated throughout the rainwater harvesting system.
The water is then sealed containment of distilled water with some particles below 500 micron (due to pre-storage filtration) and bacteria. All of which is completely removed before end use.
Well Water – Well water at some point was rain, despite it being in an underground aquifer, at some point it went through the water cycle. It fell from the sky, collected carbon dioxide, landed on the earth, whether on a landfill, crops, collecting formic acid through decaying vegetation, maybe it fell on fertilizer, we don’t know what it could’ve picked up on the surface. It then soaked into the earth, passing layers and layers of rock and earth, it then goes through the cracks of bedrock, where it is collected with other water which flowed through different paths of contaminants.
These contaminants include naturally occurring fluoride, calcium, magnesium, iron, hydrogen sulfide gas, and more. It is factually flawed to say that well water is somehow better than rainwater.
Spring Water – There is a popular misbelief that the quality of spring water is with close to no flaws, and while it is true that spring water is often naturally soft water (so is rainwater by the way), it is also very likely to have many more harmful contaminants to human health since it is much closer to the surface and didn’t have the chance to filter down through the rock, sand, and bedrock like well water.
Surface Water – Surface water (Rivers, lakes, and streams) is by far the worst type of water that one can use for water supply. Many people don’t know this, but most lakes and rivers are kept filled by underground water supplies. So all the contaminants that make up spring and well water are in the surface water, but also naturally occurring runoff takes place which includes parking lots with oil, city stormwater runoff, and whatever else could be on the ground that is washed away into the lakes and rivers.
Municipal Water – Municipalities most often collect their water from either surface water or well water. In the midwest, wells are more commonly used. They use large 12″ well casings and pump massive amounts of water out of the groundwater supply (read this article to learn more groundwater depletion), which all to say, is not a sustainable method. But in the east, it is much more common to draw from lakes and rivers for water supply, which is surface water.
There is a lot to say about the quality of municipal water, so we wrote an article about it – Read it here.
But to give you a synopsis, there are many chemicals used in the filtration process, water is most often hard, and it is impossible for the municipalities to know what every home is receiving in terms of water quality. There is so much more to say, so go read that post.
Water – All water goes through the water cycle, so one could say that everyone is already harvesting rainwater, it just depends at which point the water is collected. No matter if it’s well water, spring water, surface water, or municipal water, you cannot know what’s in your water and control it. But with rainwater harvesting, you take complete control of your water source.
Why Pre-Storage Filtration is Important for the Ecosystem
After it lands on the roof, rainwater flows into the gutters, and through the downspouts. Conveyance is connected to the downspouts and takes the rainwater to the rainwater storage tank. Prior to entering, the rainwater goes through a pre-storage filter.
The filter highly oxygenates the water which is important for in-tank health, and removes contaminants such as leaves, large particles, and suspended solids over 500 micron. The pre-storage filter is most often made from a metal mesh and should never need to be replaced, but must be cleaned about two times per year to maintain efficiency.
Removing the large contaminants and particles is crucial in the overall rainwater harvesting system. Without this step, other processes and filtration will not work effectively, causing the system to not reach its full potential.
Water Enters the Storage
From the pre-storage filter, rainwater enters the tank. The water enters the tank so as to not disturb the biofilm at the bottom (info on biofilm below), in an inward and upward motion.
Groundwater Recharge | Overflow
When the rainwater fills the tank completely, water is sent through an engineered-design overflow device that allows water to exit the tank and go into groundwater recharge or other selected source, without comprising the inside cleanliness of the tank.
Biofilm – The Natural Water Cleaner
Did you know that while in storage, rainwater is being cleaned continuously? Let me introduce you to the biofilm. The biofilm is a naturally occurring blanket of microorganisms that layer on the bottom of a properly designed rainwater harvesting tank. And while a layer of bacteria in a water storage tank would sound bad, it is actually very healthy for the water.
Scientists have conducted research on the biofilm in rainwater storage and its benefits for over 15 years. The biofilm acts as a natural filter, continuously removing particles in the water and helping maintain the primary goal of rainwater storage.
Exiting the Tank
It is not only important how the water enters the tank, but also how it exits. Using a floating filter intake, the water passes through yet another filter on its way out of the tank. It is collected just a few inches under the surface, where the water is at it’s best.
The Goal of Rainwater Storage
The primary goal for the rainwater while in storage is to meet 3 factors: Clear, odor-free, and slime-free. When these three factors are met, it is a good indicator of a successful rainwater water storage design.
U.V. Resistant Storage
The ultraviolet rays from the sun can cause algae growth within the tank which can lead to a host of problems and also keeps the water from reaching the goal of clear, odor-free, slime-free. Because of this, proper rainwater harvesting design will include ultraviolet-resistant storage.
It is important that the tank used is designed for potable use. Materials can leach into the water when using a tank for the wrong application. All rainwater harvesting tanks should be NSF-61 certified to assure no leaching will take place.
The beautiful reality of rainwater storage is that it is a self-maintaining system. This is only true, of course, if designed and built properly with correct components and processes in place. This is actually a serious reason why most DIY rainwater harvesting systems fail, certain parts will be used improperly, the storage tank doesn’t work for the application, filtration components are wrong, aeration doesn’t take place, switches, wiring, and controls are installed incorrectly, and many others.
Hiring a professional rainwater harvesting system turnkey supplier/installer is a sure way to obtaining great quality, safe, healthy rainwater for your entire home.