By analyzing 55 years of location-specific daily rainfall data, Cleanflo can determine the maximum potential volume of rainwater that is actually usable based on:
- Daily Rainfall Data
- Water Demand
- Storage Tank Volume
In real world scenarios a system can never reach ‘maximum potential’ because there is loss from the roof, pre-filter, and tank overflow events. Also, the size of rainwater storage tank and how much water is used daily from the tank play an important role in determining how much rainwater you can actually collect and use. Actual useable rainwater forms the basis to determine 'return on investment', because storage tanks are the single most costly item in a rainwater harvesting system, determining the smallest tank size that will collect the most water based on the three criteria listed above, will significantly impact the total cost of your rainwater harvesting system.
All daily rainfall data was obtained from Environment Canada from almost 400 stations across Canada, for 55 years, from 1955 to 2010.
Our software automatically selects the geographically closest station to your project site, feel free to view our station list (Station List)
Rainwater harvesting systems are designed with water demand in mind. The use of incorrect water-figures can result in a system that is either over, or under designed. In the case of an under-designed system, the system may be unable to consistently meet the daily water needs of its users requiring the tank to be topped-up from hauled water or a secondary water supply. In the case of an over-designed system, potentially wasted capital investment.
In either situation it is critical that the water demand value employed in the design process be as representative as possible.
There are two methods to determine the the Water Demand.
- Historic Records - Water records or meter readings that provide an accurate water demand.
- Estimations - Cleanflo estimates your water demand based on:
- Number of occupants
- Days used per week
The Rainwater storage tank is the heart of the rainwater harvesting system and should be carefully selected. Cleanflo identifies the optimal tank size to maximize water savings, when any larger tank would provide only a small additional amount of 'Useable Rainwater'.
Tanks are sized by the following criteria:
- 15% "Dead space" -
- Rainwater harvesting tanks often have unused volume referred to as “Dead space” to account for, undisturbed rainwater at the bottom of the tank, and the head space at the top of the tank.
- Rainfall Collection Loss -
- Not all rainwater contacting the catchment surface (roof) is collected in the tank, some is lost due to collection loss. Initial loss factor - The initial amount of rainfall loss before collection takes place, Continuous loss factor - the percentage of rainfall that is lost during the rainfall event (due to roof, wind, leaky gutters, etc.)