Collecting Rainwater for Toilet Flushing
by Jim Harrington
In our home in Atlanta, The Original Rainwater Pillow system initially installed for irrigation has now been adapted to supply water to flush toilets. The plumbing code in Georgia requires that the rainwater be of potable water standards. This is accomplished by adding a second filtration system as described below.
The first step was to determine how much water flow is required to flush the toilets. We upgraded our pump to an on demand pump that will provide 2.5 gallons of water per minute. A demand pump is necessary because toilets are designed with float valves that control filling the tank.
Once the water flow of 2.5 gallons per minute was determined as sufficient, we were able to specify an Ultraviolet Light disinfection system. UV systems are rated by flow requirements.
As the water is pumped from the pillow, it flows through a series of filters prior to exposure to the UV light. The first filter is 20 microns which removes the larger debris thus extending the life of the second 5 micron filter. Cleaning the water down to 5 microns is required for most UV light disinfection systems. Biological agents will be removed by this filtration, followed by UV light treatment thus creating potable water.
Lastly, often a charcoal filter is added to help reduce any odors and chlorine. In our system, we will not be including a charcoal filter. I am pre-treating the water with an aeration system to remove any odors. This is alternative process for water that will not be consumed.
The filters and UV light need to be replaced once per year. The glass tube on the UV light will need to be cleaned 2 -3 times per year.
By diverting rainwater from our collection system for use in flushing our toilets, we will save approximately 25,000 gallons per year!
For more information on rainwater harvesting or using it for toilet flushing, visit: www.rainwaterpillow.com.