Fine mesh works

These are separate tanks one at each end of the house. Both tanks were sealed, underground and full of mosquitoes. We have been plagued with mosquitoes for years, despite our best effort to eliminate standing water that are potential breeding locations.

The only access to the sealed septic tanks is through the head of line vents projecting above the house roof, which are fitted with present versions of the plastic insect cowl.

The cowl vent slots look quite large, so we covered the vents with fine mesh.

The result is a dramatic reduction in mosquito numbers.

If we have this problem, it is quite likely every other septic system also has it.

Moreover, given the number of septic tanks in use and the health risk now posed by mosquitoes, it would seem wise for the health authorities to address the issue with better vent cowls that actually keep mosquitoes out of the system and a public education program to encourage modification of existing vents with the addition of fine mesh.