Rainwater harvesting has been around for thousands of years. One resource can date rainwater harvesting tanks back to 2600 BC in India. Of course technology has advanced throughout
the years and some of today's rainwater systems are very sophisticated systems.
The general population typically pictures a rain barrel when one mentions "rainwater harvesting." Rain barrels
are great systems for small gardeners who prefer to hand water plants. However, rainwater systems can be utilized for
much more than hand watering needs. Systems can supply water inside the home to wash clothes and flush toilets and some systems are
even the sole household water source. Likewise, rainwater systems can be designed for commercial and even industrial needs and
uses, including manufacturing processes, vehicle washing, laundry washing, etc.
Drought is a shortage, but not the absence of rainfall. Rain will still fall during
drought times and often it falls too hard for the ground to absorb and water is lost to surface runoff. Rainwater systems
will collect nearly all the rainwater that falls on the collection surface (roof). This water can then be applied to the
landscape at the appropriate rate that will allow the water to be absorbed in the ground.
Rainwater systems also allow for water storage to collect rainwater during wet seasons to reapply during dry seasons,
which often is when water demand is highest. Rainwater can also be harvested even during the winter months when rain turns
to snow. Snow covered roofs will melt and that water will be diverted to the rainwater storage tank to be stored for reuse.
Any licensed plumber can install rainwater harvesting systems. The components that make up a system are
specific to rainwater harvesting, but the components follow basic plumbing guidelines. Any plumber that is well versed in
float switches and pumps would be able to install a rainwater system.
Likewise, any septic system installer could install the tank with ease.
Properly designed systems can generate healthy water supplies. As outlined in the World Health
Organization publication, having a first flush filter will assist in removing any potentially harmful organisms from the
water storage tank. It is of utmost importance to have a first flush filter that does not clog, fail or harbor contaminants
to protect the water quality. The Wisy filters that RMS sells have a unique design that never clog. The stainless steel removable
filter dryies out between rain event, which prevents microbial growth and potentially contaminating the water supply.
Roof surfaces will have an impact on water quality. As outlined in the Virginia Rainwater Harvesting Manual,
metals roofs are ideal for rainwater systems and asphalt roofs should never be used. Copper roofing material should never be used either
as it introduces unsafe copper levels into the environment (see reference).
Water entering a tank should be calmed to prevent stirring of the tank and disturbing the biofilm, which naturally forms in
tanks. As explained in Coombes' report, biofilms are a
slimy layer that form on rainwater tank walls and floor. It is compromised of bacteria naturally occurring in soil and metals. The biofilm layer protects water quality as metals are
absorbed in this layer. Since the biofilm is made up of living organisms, oxygen is released into the water, again
maintaining water quality within the tank.
First flush filters are critical to tank health as well. Eliminating decomposing organic material like leaves,
sticks, and dead animals will prevent anaerobic conditions from forming in the tank,
which would degrade the tank water quality and even contaminate the water.
Learn about the Wisy 4-step process to promote a healthy rainwater system.
Tank water quality should always be protected no matter howe the water will be used.
Pre-filtering rainwater with a Wisy first flush filter will eliminate organic debris entering the
tank. Lack of pre-filtering will allow sticks, leaves, dead animals, etc. to enter the tank and will cause anaerobic
conditions, which results in cloudy, foul smelling water. Also, organic matter in the tank will require cleaning and will
clog hoses and irrigation heads. Money saved from excluding a Wisy pre-filter will be spent eventually for maintenance and may
even cost more money than initially saved.
Properly designed rainwater harvesting systems require minimal maintenance - that includes never
cleaning the tank. Due to the presence of beneficial biofilm in the tank (as reported here),
cleaning and disinfecting a tank would remove this beneficial layer. Tank cleaning should only be done if organic debris is allowed
to enter the tank, which would result in anaerobic conditions with foul smelling and unhealthy water. Appropriate pre-tank
filtering removes such organic debris to protect water quality and allow for the development of the beneficial biofilm layer.
There are many first flush filters on the market today and all are designed with the theory that the first
water that comes off the roof is the dirtiest and should be diverted from the water storage tank. However, not all first flush
filters are the same way and operate with the same efficiency. Some filters require initial water to fill up a well and
then once that well is full, the additional water is diverted to the storage tank. These types of first flush filters are described
here. These systems require maintenance as the well systems must
be cleaned often to remove any organic debris that gets trapped. If debris is not cleaned, the decaying debris will start to smell
and will jeopardize the health of the water in the tank.
The Wisy first flush filter uses a vortex action to separate the organic debris from the clean water. The first flush of water
that flows from the roof to the filter is diverted to the first flush outlet. Once the stainless steel filter insert is fully
saturated, the filter starts to collect clean rainwater and diverts it to the storage tank.
Many people wonder how water flows
to the side, storage tank outlet, and not straight down to the first flush outlet. Water follows the rules of adhesion and cohesion - meaning it
sticks to surfaces and itself. When the water enters the filter it sticks to the sides of the filter and once the filter is
saturated, it sticks to the filter as well. The water swirls around the filter and enters into the first outlet - the storage tank
outlet.
The highly engineered Wisy filters never clog and require cleaning 1 to 2 times a year (as opposed to after
every rainfall like other filters!). The stainless steel filter is self-cleaning due to the vortex action. As reported in the World Health
Orgizantions's report, "In order not to waste precious rainwater, inlet
filters should have capacity to handle larger amounts of water and should therefore preferably be self-cleaning."
Watch how the Wisy filter works - notice the vortex action of the water in the filter and the water flowing out of the storage tank outlet.
Rainwater harvesting systems are not "one size fits all." The appropriate tank size depends on:
roof area
local rainfall
intended use
Tanks should be small enough to overflow regularly to provide skimming of the water surface, but large enough to provide a
reliable water supply. one article
covers the supply and demand balance to sizing the appropriate rainwater harvesting tank.
Typically, the largest expense in a rainwater harvesting system is the tank. Choosing the right tank size can make a difference
in overall cost savings and investment payback.
Misusing the term "greywater" for "rainwater" happens often, but the two are very different.
Rainwater is the water that falls from the sky. Greywater is water that has already been used. An example of greywater
is the water that has been used to wash clothes is collected and reused to irrigate a lawn or to flush a toilet. The
treatment regulations for using rainwater and graywater are drastically different. Graywater can never be reused
for drinking water. Rainwater, however, once it undergoes treatment (i.e. carbon filters and UV light treatment)
can be consumed as drinking water.
In summation: Rainwater is collected from a roof system and is used for washing clothes. Greywater results from the clothes washing and is reused in the toilet. Black water is the resulting water from toilet use and is diverted either to a water treatment system or to a septic system.
