One of the major benefits of designing a building with siphonic roof drainage and rainwater harvesting systems is reduced overall construction and facility operation costs.

Additional benefits include reduced discharge of rainwater to lakes, streams, rivers and sanitary systems, and decreased dependence on municipal water supplies.

Benefits of Rainwater Harvesting:

1. Industrial and Commercial Use

a. Water conservation
i. site irrigation,
ii. toilet and urinal flushing,
iii. janitorial use, and
iv. fire protection.

b. Reduced municipal water consumption and industry uses
i. car washes,
ii. commercial laundry,
iii. process water (e.g., microelectronics, metal molds, electroplating, printing, etc.),
iv. evaporative cooling tower make-up,
v. mechanical equipment make-up water, and
vi. evaporative cooling of roof surface (reduction in A/C load).

c. Stormwater runoff reduction
i. assists storm water NPDES permitting,
ii. allows for better use of property (e.g., less area used for on-site detention),
iii. above ground and below ground storage (cisterns) reduce mosquito nuisance on site,
iv. decreases soil erosion and local flooding by reducing run-off rate and quantity, and
v. improves water quality to near by streams, rivers, and water sheds.

e. Promotes good public relations (i.e., showing a positive environmental concern by eliminating run-off).

2. Military Use

a. Can be used for all industrial/commercial uses listed above,
b. decreases dependency on delivered water supplies, and
c. can serve as reserve source if primary water supply is contaminated.

3. Residential Use

a. Water conservation
i. lawn and garden irrigation,
ii. toilet flushing,
iii. laundry,
iv. car washing,
v. filling pools and hot tubs, and
vi. residential fire protection supply (can reduce insurance premiums).

b. Reduced dependency on strained municipal water supplies
i. reduce monthly water bill by reducing municipal water needs,
ii. avoid water restrictions by collecting your own water,
iii. reduce or eliminate need for water treatment systems (e.g., softeners), and
iv. adds sale/resale value to homes with reduced water bills and fewer water restrictions.

4. Supplement or replace well sources of low yield or water quality

a. Rainwater is naturally soft (low in mineral content)
i. reduces/eliminates water softening equipment, and
ii. reduce the amount of detergent needed for laundry.

b. Can be used to supplement low volume wells instead of drilling additional or deeper wells.
c. Can enable development in areas without sufficient municipal or well water sources.
d. Can enable development adjacent to wetland areas and streams due to reduction in rainwater discharge rate and quantity to surrounding waters.
e. In many cases can be used as potable water supply (can be completely “off the grid” where necessary).