Straightforward Mosquito-Proof Rainwater Tank – Mom Earth Information


When warm weather finally hit the Missouri Ozarks this spring, I wondered if I had to drain my newest rain-collecting system before it turned into a mosquito repository.

I want to encourage the reproduction of several useful lower life forms here, including earthworms, ladybugs, toads, and lizards. Snakes are also very welcome. Mosquitoes are not on my list of protected species, however. Aside from the diseases they transmit, a swarm of pesky skeeters will rush me into the house and scream how I miss winter.

Last spring, my husband surprised me with a fancy 425-gallon portable storage tank, one of the most beautiful gifts of my life. Since we don’t have any cattle, we instead leveled a spot for the tank to collect rainwater under a downpipe. But by the drought of the century, it was August before there was a level of moisture in the tank. But wow, was this nutritious rainwater ever appreciated when it finally arrived. My dried out plants loved every drop.

The tank came with a threaded cap that we replaced with a circle of window grilles. My husband drilled numerous holes in the bottom of an old flour canister that fitted snugly into the opening, then placed it on the sieve. The downspout, a section of 6-inch PVC pipe, is inside the canister, which holds the strainer in place and allows any accumulated leaves to be easily drained.

I made a remarkably sunproof cover for the tank by sewing recycled bedsheets together (on my trusty pedal, of course) and then painting the fabric with some leftover green enamel paint. The fabric cover provides sufficient shade for the tank to prevent algae growth, even if it is more than 100 degrees Celsius, and should extend the life of the plastic tank.

I suspect mosquitoes hate the dome-shaped device as they are banned from their preferred habitat – warm, still water. Did you know that mosquitoes can multiply in 10 days? In wet weather, even a cow’s muddy footprint provides a breeding ground for them. I’m not that gifted at math, but expect it to be a multitude of mosquitos in no time.

The 70-gallon storage tank I brought home from the local thrift store for $ 20 doesn’t have such a domed lid. While conveniently exposed right outside my greenhouse door, I knew that preventive mosquito measures would soon be required. I’d read about a variety of techniques, like chemical dunks, goldfish, and a little bit of vegetable oil, but none was exactly what I was looking for.

When I complained about what kind of device would keep winged bloodsuckers away and still allow me to soak in my 2 gallon watering can, my innovative husband showed up.

Incidentally, a few years ago I casually mentioned that I wanted a scarecrow to keep the birds from stealing my pumpkin seeds. My husband fused PVC pipe, galvanized metal fence wire, and 2 x 4 inch wood to create a fully clothed, rotating, life-size mannequin with articulating arms that shook shiny cake tins against potential intruders. The scarecrow worked well not only for birds but also terrified squirrels, rabbits, and raccoons, and eventually became a popular family member. We called him Woody.

I can just throw a sheet over the storage tank, I muttered when I remembered Woody.

My husband walked past me, made a lot of noise in the shop, and stormed back with an arm full of tools and supplies. “Here. Take a picture of it,” he said and threw the stuff on the floor.

That’s it? I wondered.

In less than 30 minutes we put together a simple, sturdy strainer and plywood cover to keep the mosquitos out and let me and my watering can in. You don’t have to worry about increasing the bug population.

Build your own

First, place a slice of window grille material over the tank, leaving enough space for your watering can. Fold the open end under the raw edge a few times to stabilize it. We used an aluminum shade, but I suspect a nylon shade would work just as well. Drape the strainer over the tank sides, trim it to allow for an overhang of about 4 inches, then use a strong rope to securely tighten it. Use a razor to cut an opening about 1/2 inch smaller than your downspout so it fits snugly.

Next, cut a sheet of plywood that is at least 4 inches larger than the width of the tank and the length of the opening. Underneath, screw strips of 1 1/2 by 1 1/2 inch scrap wood on three sides to hold the cover in place and to keep the plywood from warping. Screw on another wooden strip as a handle and to hold the lid rigidly over the screen. We converted an old plywood sign from a manufacturing company so that one side was already varnished. I just primed the remaining raw wood surfaces and called them good.

I can already see the excitement of the mosquitos floating over the adorable water tank but not coming in to reproduce. The cover and tank may not be as nice as our old buddy Woody, but they cost little and should protect our rainwater for many seasons of the year.

In the meantime, we’re writing down ideas for more rain collection systems, including the inventive garden rainwater facility that Cheryl Long, editor of Mother Earth News, wrote about in the August / September 2012 issue.

Photos by Linda Holliday

Linda Holliday lives in the Missouri Ozarks, where she and her husband founded Well WaterBoy Products, a company dedicated to helping people live more off the grid, and who invented the WaterBuck pump.

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