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Frequently Asked Questions
about the FreeRain System
and Water Harvesting

Q: What treatment is required of the harvested rain water for toilet flushing? Irrigation?
A: Currently the revised NC Building Code requires that harvested rainwater that is used for toilet flushing be disinfected and dyed blue or green. No treatment or dying is required for harvested rainwater that will be used for irrigation.

Q: Is the disinfectant and color dye harmful to my lawn?
A: The harvested rainwater that irrigates your lawn will NOT be disinfected or colored. FreeRain uses a disinfecting and color dying system that only treats the water entering the building for use in toilet flushing or cooling tower make-up water.

Q: How do you size the FreeRain cistern for the project?
A: The ideal tank size depends not only on the impervious square feet (e.g. roof) of the property, but also on the projected usage of the harvested rainwater. For toilet flushing applications in a commercial or government office building, we often size the tank by calculating the gallons demanded per day multiplied by the number of days of storage that the owner prefers. Sizing the system for irrigation purposes requires knowledge of the gallons demanded for one irrigation cycle and the square footage of roof (or other surface) that will be used to harvest water. While the calculations inform our decision, the final tank size depends on the owners investment preferences. As the tank size increases, the water savings increase. The owners LEED certification goals must be considered too.

Q: How much water do you capture for each square foot
of impervious area?

A: For each square foot of impervious area you capture about .62 gallons for each inch of rain fall.

Q: What credits do you receive for a cistern from N.C. DWQ (the North Carolina Division of Water Quality) to offset the size of the Best Management Practice (BMP)?
For each gallon that you are able to store in your cistern you get a 1:1 credit that can be used to decrease the size of your BMP. Currently, the DWQ only allows the credit to apply to rainwater harvested off rooftops. The DWQ Technical Guidance for Rainwater Harvesting is on the Stormwater Permitting Unit home page. (See the "Rainwater Harvesting" link on about line 5 or 6.)

Q: Where else are cisterns used in the country? How progressive is the Triangle in terms of cistern use/policy?
Rainwater harvesting has been in practice for many years in the western part of the country where the systems are a necessity because of the extreme water shortages. The Southeast is catching up and Georgia has introduced some policies and codes encouraging rainwater harvesting. The Triangle is becoming increasingly aware of our water shortage problems and in the last couple of years has begun recognizing rainwater harvesting as a proactive solution. Some of the current rainwater codes and regulations in this area are not as progressive as in other parts of the country but they are continually evolving and heading in the right direction.

Q: Can my existing building or residence be retrofitted
with a FreeRain System?

A: Yes, most buildings can be retrofitted with a FreeRain System. Obviously, there are additional challenges in accessing the site and establishing the conveyance system but FreeRain has a variety of tank options and solutions for your retrofit project.

Q: What is the required maintenance of a FreeRain System?
Very little. Like irrigation systems, FreeRain does need a winterization before freezing and a start up in the Spring. The filters have an automatic backwash to keep them clean. Also periodically the catch basin should be checked and any leaves and debris removed. The tanks themselves should require no maintenance. FreeRain has systems which have been operable for 10+ years and these tanks have never required pumping or cleaning.

Q: What effect does a “green roof” have on the ability
to harvest rainwater?

A “green roof” has plants, trees and grasses planted on the roof to increase the building’s thermal efficiency and to reduce runoff. Obviously, the result is a rainwater harvesting system will need to rely more on harvesting water from other impervious surfaces such as parking lots because the “green roof” will have a lower runoff coefficient than a typical flat, metal or shingle roof. A FreeRain System can be utilized to irrigate a “green roof” during periods of low rainfall to ensure that the plants stay healthy.

Q: What is my municipality’s policy regarding cisterns? Will they require testing or monitoring?
Current regulations in North Carolina do not allow a municipality or any other organization to prohibit the use of a cistern. Each municipality is different in their policies regarding testing and monitoring of the systems, but most do not require anything. Please contact FreeRain and we will investigate what would be required to install a cistern for your project.

Q: If rainwater harvesting systems are so great, why do I not hear of more systems being installed and used?
A: Rainwater harvesting systems are still relatively new to this area but FreeRain has installed systems over the last 10 years. As green building and LEED become more prevalent the use of rainwater harvesting systems will become more widespread. Also since FreeRain tanks are buried underground and very little is visible from the surface your neighbors will probably not even realize that you are utilizing a system.

Q: What are the obstacles preventing widespread adoption of rain water harvesting systems?
The main obstacle is changing people’s perspective that water is a cheap and unlimited resource. While the cost of potable water in most municipalities is not even a penny a gallon, as the area grows our finite water sources will beginning running out and building additional reservoirs and water treatment facilities will cost taxpayers billions of dollars. Once the general public recognizes that not only are FreeRain systems the environmentally right thing to do but also will save them money they will push local and state governments to pass more progressive and proactive policies to encourage rainwater harvesting. FreeRain believes in the near future rainwater harvesting will be recognized as an important part of the solution to our water crisis and the systems will become widely used.

Q: How much does a FreeRain system cost? And what is my payback period?
FreeRain is customized for each individual project. Depending on the project the size of the tank used, type of tank, assess to the jobsite etc. are all variables that affect the cost. Please contact us at (919) 460-1180 for a free consultation and estimate. The same it true of the payback period. For some large commercial jobs FreeRain pays for itself on DAY 1 as a replacement solution for more expensive BMP’s or high irrigation tap fees. For developers FreeRain may create more developable area if the cisterns can replace land consuming water retention ponds and this could pay for the FreeRain system several times over.

Q: How much of a difference does the installation of a FreeRain system make in the grand scheme of our areas water shortage problems?
Rainwater harvesting could make a dramatic difference. In a typical office building, 90% of the water used is for non-potable usages, and in a residence irrigation can account for up to 50% of total water usage and toilet flushing 20%.

Q: What can I use rain water for?
A: The most common uses for rain water are landscape irrigation and toilet flushing, but there is wide range of uses for non-potable rain water such as; car washing, make-up for cooling systems, washing down parking lots, wetting clay tennis courts, etc.

Q: What types of tanks does FreeRain use?
A: FreeRain Systems utilize a variety of tanks. We often use underground concrete tanks because we have found those to be the most cost effective solution. However, some institutional and government clients like state building and museums prefer above ground tanks so that they draw attention and serve an education purpose.

Q: Can the FreeRain System help me with nitrogen reduction requirements?
A: Yes. The FreeRain System itself gets 0% nitrogen removal. The downstream BMP (i.e. sand filter) still controls the overall nitrogen removal rate, but the storage volume of the sand filter can be reduced by the volume provided by the FreeRain System. So you can eliminate some sand filter - equal to the volume of the FreeRain that will be drained in 2-5 days - and the overall nitrogen calculation stays the same. See the "DWQ Technical Guidance" linked herein for more information.

Contact FreeRain today to learn more about how our rainwater harvesting system can benefit your current or future projects.

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