The following information was used to review and learn what is necessary to understand the concepts of design and implementation of a rainwater catchment system for the La Yuca rainwater catchment 2013 project.

Rainwater Catchment System[edit | edit source]

A rainwater catchment system is a system that collects, filters, and stores rainwater for community or household use.[1]

Roof Types[edit | edit source]

The type of construction material is important for a rainwater catchment system. Depending on what material is used for the roof, the collected water can be contaminated by carcinogens.[1]The roofing materials used in a rainwater catchment system should be chemically inert to keep contaminants out of the system. These materials include aluminum, fiberglass, plastic, and wood.[2] In addition to the roof material itself, the climate can influence the contaminate runoff depending on the material.

Metal roofs are commonly used for their smooth texture, Galvalume (55% aluminum, 45% zinc alloy coated sheet steel) is commonly used and can be treated with epoxy paint or a baked enamel coating. Clay and concrete materials are available for potable systems, clay and concrete are porous, however, which can lead to water loss, evaporation, and bacterial growth. Composite shingles should not be used for potable catchment systems due to the leaching toxins, in addition, wood shingles, tar and gravel are also know for leaching compounds and are therefore unsuitable. The most ideal roofing material for rainwater catchment is slate because of its smooth texture and lack of toxins. The cost of slate can be very high.[3]Various roof paints for roofs are suggested by the National Science Foundation to prevent leaching of carcinogens into the rainwater.[4]

Water Treatment Techniques[edit | edit source]

Water from a rainwater catchment system must be treated before it is considered potable. Techniques for cleaning water vary depending on what filters are available and the contaminants involved. "No one piece of treatment manages all contaminants".[5]

Treatment Result
Leaf screens and strainers prevents leaves and other debris from entering the tank
Sedimentation settles out particulate matter
Activated charcoal removes chlorine
Roof washer eliminates suspended material
In-line/multi-cartridge sieves sediment
Activated charcol removes chlorine, improves taste
Microbiological treatment/Disinfection
Boiling/distilling kills microorganisms
Chemical treatments(chlorine or iodine) kills microorganisms
Ultraviolet light kills microorganisms
Ozonation kills microorganisms
Nanofiltration removes molecules
Reverse osmosis removes ions(contaminants and microorgaisms)
Treatment techniques[3]

Water Quality[edit | edit source]

There are three criteria to having acceptable quality drinking water.

  • No fecal bacteria
  • No harmful chemicals
  • No bad taste or smell

Rainwater catchment systems have commonly found contaminants due to the location and isolation of rooftops.

Common contaminants of rainwater catchment systems[6]
Contaminant Source Risk of entering Rain Tank
Dust and Ash Surrounding dirt and vegetation
Volcanic activity
Moderate:Can be minimized by regular roof and gutter maintenance and use of a first-flush device
Pathogenic Bacteria Bird and other animal droppings on roof, attached to dust Moderate:Bacteria may be attached to dust or in animal droppings falling on the roof. Can be minimized by use of a first-flush device and good roof and tank maintenance.
Heavy metals Dust, particularly in urban and industrialized areas, roof materials Low:Unless downwind of industrial activity such as a metal smelter and/or rainfall is very acidic (this may occur in volcanic islands)
Other inorganic

Contaminants(e.g. salt from seaspray)

Seaspray, certain industrial discharges to air, use of unsuitable tank and/or roof materials Low:Unless very close to the ocean or downwind of large-scale industrial activity
Mosquito Larvae Mosquitos laying eggs in guttering and/or tank Moderate:If tank inlet is screened and there are no gaps, risks can be minimized.

The Dominican Republic has the similar water quality standards as the World Health Organization (WHO).

Translated water quality standards for the Dominican Republic[7]
Parameter (mg/L)
Surface Tension Agents 0.0
Chlorides 250
Chlorine 0.00
Copper, Cu 1.0
Iron, Fe 0.3
Magnesium, Mg 150
Manganese, Mn 0.05
Calcium, Ca 75
Phenol compounds such as phenol 0
Sulfates, SO4 250
Zinc, Zn 5
Total Dissolved Solids 500
pH 6.5<X<8.5


First Flush[edit | edit source]

The first flush in a rainwater catchment system is used to clear the roof of debris and airborne residue before it can reach the storage container. The gutter and leaf screen can keep larger debris out of the first flush.[3] Generally the first flush is meant to catch the first 10 min of rainfall, as that is a difficult volume to quantify one suggestion is to divert at least 10 gallons for every 1000 square feet of roof area, an Australian vendor suggests between 13 and 49 gallons per 1000 square feet of catchment surface. The two kinds of first flush diverters include just using a a PVC standpipe, when the standpipe fills the rainwater is diverted to the storage tank. The second kind is a the ball valve, a flouting ball within the PVC pipe shuts seals off the first flush volume and diverts the water.[11][6]

Maintenance[edit | edit source]

Rainwater catchment systems require consistent upkeep in order to reduce the amount of contaminants.

Periodically OR Every Few Rainfalls

  • First flush must be cleaned

Every Month

  • Primary screen the gutters and any gutter screens must be check for damage or clogging
  • 1/4 cup of chlorine must be added per 1000 gallons[3]

Every Year

  • Tinaco (or storage tank) must be emptied of sediment and disinfected
  • Sediment and Carbon filters must be replaced[12]

Climate[edit | edit source]

The Climate in Santo Domingo is tropical, with year round high humidity, warm temperatures, and varying rainfall. Santo Domingo receives an annual average rainfall of 57 inches. During the wet season (May - October) Santo Domingo receives between 5.5-7.4 in of precipitation monthly. During the "dry" season there are 2.1-3.9 inches of monthly precipitation. The annual temperature remains relatively constant year round, ranging from 24.4-27.1 °C[13]

References[edit | edit source]

  1. 1.0 1.1 Palau Catchment Manual
  2. Rainwater harvesting from rooftop catchments
  3. 3.0 3.1 3.2 3.3 Texas water harvesting manual
  4. National Science Foundation approved list of paints
  5. University of Nebraska, Drinking Water Treatment: Sediment Filtration
  7. ANTEPROYECTO II NORDOM 64 (3ra. Rev.)
  8. WHO World Health Organization Water Quality PDF
  9. Dominican Republic water quality
  10. Guide to workplace use of non-potable water
  11. First Screening video example
  12. Rainwater catchment maintenance manual
  13. World Meteorological Organization
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Authors Camille Penny
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Created August 5, 2013 by Camille Penny
Modified June 9, 2023 by StandardWikitext bot
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