How to Keep Mosquitoes Out of Rain Barrels

painted rain barrels

Rain barrels are growing in use as homeowners try to become “greener” and as water is becoming harder to get. You shouldn’t drink water that has been sitting in a barrel, but your grass and plants can. However, you must know how to keep mosquitoes out of rain barrels or face their nuisance factor – and the diseases they can bring.

In some cases, people opt for something larger, such as a cistern. However, a cistern has the same concerns as a rain barrel. Still, both provide for rainwater harvesting. We’ll show you how to keep mosquitoes and other critters out so you can harvest the rainwater insect-free.

Steps to Take

rain barrel with mesh top
Photo Credit: Justin Smith / Canva Pro / License

Rain barrels are designed to keep mosquitoes out. But all the mesh and caulk you use may not keep out all the mosquitoes. 

There are things you can do with your collected rainwater that will help with mosquito control:

  • Put in vegetable oil or cooking oil. Put in a ¼ cup once a week and after a storm. The oil will put a film on the surface of the water that will suffocate mosquito larvae that show up.

An alternative: Spoon in liquid dish soap. One tablespoon per week. It puts a film on top of the water, causing female mosquitoes to drown before they can lay their eggs. But be sure to use soap that won’t damage plants later.

  • Drop in Bti as a larvicide. A naturally occurring bacterium found in soils, Bacillus thuringiensis israelensis slowly dissolves, releasing material that will kill mosquito larvae. Commercial products that contain Bti are widely available in doughnuts or granules. Government agencies use and recommend Bti products as well.
  • Drain or use all of the water within five days. That removes standing water before mosquitoes can go from egg to adult, and prepares the rain barrel (by making it empty) for the next rain.

Preventative Measures

graphic for How to Control Mosquito Populations vertical
Photo Credit: Juan Rodriguez

Rain barrels can quickly become the perfect place for mosquitoes to breed. To prevent mosquito breeding in your water catchment system, follow these tips:

  • Use: Water that is gathered in the barrel needs to be used right away. The barrel must stay dry between rains.
  • Fix: Repair damage to the barrel or screens that are worn, openings that are clogged, and lids that have become loose.
  • Dump: If you even think that mosquitoes are using your barrel to lay eggs, dump out any water immediately. It will get rid of any larvae that mosquitoes have placed inside. If there is stagnant water, dump that out right away.
  • Scrub: Make it a point to scrub the inside of the barrel annually, using vinegar or warm, soapy water. It will get rid of any mosquito eggs that were attached to the walls on the inside.
  • Store: If you live in a place that gets snow and ice in the winter, rain barrels should be emptied and covered or turned upside down so there is no water to freeze, or be moved to a storage shed.

Where Mosquitoes Try to Get In to Rain Barrels

graphic showing how a rain barrel works
Infographic by Juan Rodriguez 

1. The opening on the top: Keep a tightly-sealed screen on it. Or use a fine mesh, one with openings of 1/16th of an inch.

2. The lid around the opening: Use a smooth one. The fancy ones have designs on which standing water can sit.

3. The overflow port: It keeps water from spilling out of the opening on the top, but it can also provide a way for mosquitoes to get in. Put a mesh screen around the opening. 

4. The faucet: Put a mesh screen around the opening. Keep the valve closed. Water will sit on the inside of the barrel below the valve; dump out the barrel to prevent that. 

Note: Hoses and downspouts should not feed directly into the rain barrel. An air gap is required so that water must pass through the screen of the intake opening.

A pro’s tip: Keep a hose attached to discourage mosquitoes from trying to fly in through the faucet.

What Rain Barrels Can Be Used For

Photo Credit: Katie Elzer-Peters / Flickr / CC BY 2.0
  • To water lawns and gardens outdoors. In the average home, 30 percent of its water use goes to the lawn and gardens, according to the Environmental Protection Agency. However, there are places in which the outdoors accounts for 60 percent of a family’s water use, a concern in this age of water conservation. 
  • To water plants indoors, but be even more careful with fruits, vegetables, or other things you plan to eat. Unlike outdoor plants, indoor plants seldom have enough soil to filter the water (and in both cases you should water the soil, not the plant directly).
  • Washing the car
  • Window washing
  • Cleaning outdoors areas, such as driveways, paths, and patios 

Using a rain barrel will save a home up to 1,300 gallons of water during summer, according to the EPA.  

Remember: A rain barrel is catching water that is coming off the roof. While the water that fell is pure, the roof that it is rolling across can have dust, leaves, pollen, and pesticides – and gutters are primary spots for mosquitoes to lay their eggs.


What Diseases Are Spread by Mosquitoes?

Mosquitoes spread these diseases to humans, roughly in order of concern:
● Malaria 
● Yellow fever 
● West Nile virus
● Eastern equine encephalitis
● Dengue
● Chikungunya 

Mosquitoes transmit these diseases to animals, both pets and livestock:
● Dog heartworm
● West Nile virus 
● Eastern equine encephalitis

Can I Make My Own Rain Barrel?

Yes, it is possible to make a rain barrel as a DIY project. Start by gathering these supplies:
● 55 gallon plastic barrel
● Small brass faucet
● Small garden hose adapter 
● Two locknuts
● Plumber’s tape
● Caulk
● A mesh screen

You put the faucet near the bottom and the garden hose adapter near the top, using the locknuts, tape, and caulk. You put the screen across the top of the barrel. 

A pro’s tip: Avoid decorative tops: They will provide a place for standing water. If you want to make it attractive, you can paint the outside of the barrel. Some painted barrels are quite attractive.

Where Do You Place Your Rain Barrel?

A rain barrel is best placed under a downspout located at a:
House. In can be painted or otherwise dressed up to become a design object
Garage, especially if it is a stand-alone.
Shed, no matter the size
Garden near a wall. Keep it in mind as you draw up plans.
Gazebo. There is a solid roof, so it will have gutters.
Greenhouse. There are kits available just for this.
Pavilion, even though it doesn’t have a floor

A pro’s tip: If you have a lot of runoff, you can put two rain barrels side-by-side.

A Call to Action

Rain barrels and cisterns are valuable and fun, but you need to take care of them, especially when it comes to mosquitoes. You can handle the maintenance as a do-it-yourself project, and decide on the construction and installation.

But if you want to turn to a professional, Pest Gnome connects you to the best pest control experts in your area.

Make a decision, and take action. 

 Main Photo Credit: Selena N. B. H. / Flickr / CC BY 2.0

Ted Rodgers

Ted Rodgers has been an editor and writer for a half century at least, and has had to deal with pests throughout. His home is still standing, which is one (small) definition of success in dealing with them. He is willing to pause in his battles long enough to share what he has learned. He borrows from Beatrix Potter when he shares this truth about pests: “Tiddly, widdly, but not piddly.”