Rainwater catchment systems can vary greatly in price and payback time. Some systems will pay themselves off quickly (e.g., in systems that select inexpensive materials and where clean water is expensive), some systems will take years to pay themselves off (especially in areas where materials are expensive and clean water is very inexpensive), and some systems will pay themselves off immediately where clean water is difficult to obtain. A simple way to examine the costs is to total the construction and maintenance costs and compare them to the replaced water costs (Figure 6-1).
In the La Yuca rainwater system, two payback periods were found: one with low-cost water and one with high-cost water. The payback period for the high-cost water (specifically $1.25 per five-gallon jug) was approximately 1.7 years. The payback period for the low-cost water (specifically $0.50 per five-gallon jug) was approximately 5.2 years. The yearly steps up in the rainwater catchment system line represent the filter replacements. These filter replacements are paid back quickly in both the high-cost and the low-cost water scenarios.
Ultimately it is up to the users to determine the value of the system.