One Neglected Swimming Pool Can Produce Thousands of Mosquitoes


As the weather starts to warm, the thought of jumping into a swimming pool is becoming more enticing; however, not all swimming pools are in good condition making them a threat to public health, as well as an eye sore. Mosquitoes can develop from eggs to biting adults in very little standing water. Hundreds of thousands of mosquitoes can come from just one neglected swimming pool putting an entire neighborhood at risk of mosquito-borne diseases including West Nile virus (WNV). What can you do about an unmaintained swimming pool in your neighborhood? If you live in Contra Costa County, you can report that pool to the Contra Costa Mosquito and Vector Control District (District).

How to Report a Neglected Swimming Pool to the District?

To report a neglected swimming pool or hot tub, call (925) 685-9301 or click here. Anonymous reports are accepted.

What Happens After I’ve Reported a Neglected Swimming Pool to the District?

If you are a neighbor, once you have reported a neglected swimming pool to the District, there is nothing more you need to do. Due to privacy requirements, we cannot share specific details about what District employees do on the property with anyone other than the residents responsible for the pool.

In a typical situation, after a neighbor reports a neglected swimming pool to the District:

The District will send letters requesting access to the pool or confirmation that it is not producing mosquitoes.

If the resident thinks the pool is in good condition, the letter directs the resident to take a picture that shows both the letter AND the swimming pool clearly and then send the picture back to the District.

If the resident does not respond to the letters, a District employee will attempt to contact the resident at home two times to request access to the swimming pool to inspect it.

If there is no answer at the time of the employee’s visits, a door tag will be left on the door with further instructions.

If the resident does not follow the instructions on the second door tag or provide access for an inspection, a final notice is mailed to the resident.

If no resolution is obtained after the final notice, a judge can issue a warrant providing access to the swimming pool for a District inspection.

If the District employee finds evidence of young mosquitoes in the water, the employee may place mosquitofish in the swimming pool to eat the young mosquitoes before they grow into biting adults. Depending upon the life stage of the developing mosquitoes present, the District employee may also treat the pool in an appropriate way to protect public health.

It is important to know that while mosquitofish reduce the risk of mosquitoes, the fish do not clean the water. A pool may continue to look very neglected, yet it is not producing mosquitoes because the fish are hard at work.

How to Prevent Mosquito Production in a Swimming Pool or Hot Tub

  1. Keep the swimming pool or hot tub in proper operating condition by cleaning, filtering, and maintaining it.
  2. Request the District’s mosquitofish service. A District employee will inspect the water feature to determine whether the fish are appropriate, and if they are, the employee will place the fish in the pool or hot tub.

The bottom line is producing mosquitoes is illegal and increases the risk of mosquito-borne disease for you and your neighbors. So, whether you can keep the swimming pool in good working order, request mosquitofish, or decide to remove it or fill it in, as long as it does not produce mosquitoes you are protecting public health for yourself and your neighbors.

About Kevin

Manager of Mainframe Operations and Optimization – USS-UPI, Co-Founder and Board Member - Friends of Oakley A Community Foundation, Trustee RD 2137, Advisory Board – Opportunity Junction
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