What to know
- Mosquitoes can spread germs that make people sick.
- Just one septic tank can produce thousands of mosquitoes.
- Mosquitoes get inside broken or unsealed septic tanks and lay eggs.
- After they hatch and grow, thousands of adult mosquitoes fly out of the broken or cracked septic tank each day.
![An adult Aedes aegypti mosquito emerges from water. Four pupae are adjacent.](/mosquitoes/media/images/Aedesaegyptimosquitopupae.jpg)
Mosquitoes and septic tanks
Mosquitoes may be laying eggs inside your septic tank if it is
- Open or unsealed
- Broken with cracks or spaces between the blocks
- Missing a ventilation pipe screen cover
![Hundreds of mosquitoes line a wall of a septic tank.](/mosquitoes/media/images/MosquitoesinSepticTank.png)
![A broken cement septic tank cover with a "no" symbol.](/mosquitoes/media/images/RepairBrokenSepticTankCoverscdcwp1583338090215_1.png)
![An uncovered septic tank ventilation pipe sticks above the groun.](/mosquitoes/media/images/Coverventilationpipescdcwp1583338113666.png)
Inspect and repair your septic tank
Check local regulations before repairing a septic tank on your own. You can work with a licensed septic tank installer to
- Seal the septic tank.
- Repair cracks or gaps in the exterior walls of the septic tank using cement or expanding foam used for home insulation projects.
- Look for a product that is made to fill big gaps and is water resistant.
- Follow directions on the product label.
- Cover vent or plumbing pipe openings using mesh with holes smaller than a mosquito.
- Fill abandoned or unused septic tanks with dirt or gravel.
![Septic tank ventilation pipe with a mesh cover. A checkmark is added.](/mosquitoes/media/images/Withscreenmeshcdcwp1583338095511.png)
![A septic tank with a concrete cover. A check mark is added.](/mosquitoes/media/images/Septictankwithconcretecovercdcwp1583338093905.png)
![A septic tank with a PVC cap. A check mark is added.](/mosquitoes/media/images/SeptictanksealedwithPVCcapcdcwp1583338091793.png)