Post-Flood Mosquito Prevention Tips

Post Date:07/03/2013

News release from Orange County Health Department

The Orange County Health Department is providing information and resources for taking care of personal swimming pools and areas of standing water. After multiple days of heavy rain, residents of Orange County are ready to begin the cleanup and drying out process, but this must be done properly.

Personal Swimming Pools (Based on the NC Department of Health and Human Services’ Rules Governing Public
Swimming Pools 15A NCAC 18A .2500,

  • Maintain the clarity of the water, so the main drain grate is visible from the pool deck
  • Disinfect the pool in accordance with the manufacturers' instructions
  • Use a test kit to sample water quality
  • Do not drain pool water into storm drains

For draining personal swimming pools, Wendy Smith, Stormwater Management and Environmental Health
Educator with the Town of Chapel Hill recommends the following: ?

  • Only release dechlorinated water (the pH range should be between 6.5 and 7.5 before discharging) to avoid killing creatures and plants
  • Wait 5-7 days before draining to allow chemicals in the pool water to dissipate
  • Emptying pool water into natural areas, such as yards and gardens in slow, small batches to minimize the risk of additional flooding from already saturated ground and to avoid soil erosion
  • Do not discharge pool water into the street or storm drain system. Discharge that enters the street can pick up motor oil, pet waste, trash, and other pollutants, carrying them into the storm drains and local surface waters

Mosquito Prevention

The first step in preventing your home from becoming a mosquito breeding ground is to reduce the amount of standing water. Typical areas where water accumulates include: wheel barrows, flower pots, bird baths, tarps, inflatable children’s pools, and clogged gutters. It is best to dump all existing water from these areas as to avoid providing an easy place for mosquito larvae to thrive.

For areas of standing water, NC State University’s Department of Entomology recommends that “homeowners wanting to treat small areas, such as bird baths, garden pools, etc., might want to try a bacterial insecticides that are available at many garden supply and retail stores. There are several products formulated as "donuts" ("dunks") or as granules that contain the bacterium Bacillus thuringiensis israelensis or "Bti". This bacterium kills mosquitoes, but does not harm fish, birds or other wildlife. The "dunk" versions are well-suited for small breeding sites (100 sq. ft. or less) and will control mosquito larvae for about 30 days.”

Source: NC Cooperative Extension,

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