Does hanging a zip-lock bag with pennies in water actually work to keep flies away? Well, it depends on who you ask...

Unsplash Via Tobias Roth
Unsplash Via Tobias Roth

Does a Zip-Lock Bag With Water and Pennies Really Get Rid of Flies?

A few years ago, right at the start of Summer, all of a sudden I had a ton of flies in my garage.

I bleached, scrubbed and pressure washed every inch of the garage but couldn't get rid of the flies.

Finally, I tried the old pennies and water in a zip-lock bag trick, and after a couple of days, the flies were gone.

Was it just a coincidence, or did the zip-lock bag trick actually work? If it did work, why?

Unsplash Via Jin Yeong Kim
Unsplash Via Jin Yeong Kim


My theory is, if this really works, is that there is some sort of chemical reaction between the copper pennies and the water that releases some sort of gas the flies don't like.

That's just my theory is probably horribly misguided. I did some digging around on the internet to see if I could find some answers and here's what I found. reports that in 2007, North Carolina State University conducted a research project to find some answers.

Well, the findings didn't conclude anything really.

From -

Researcher Mike Stringham reported on his findings after spending 13 weeks studying the effects of water bags on flies at an egg-packing plant. After meticulously counting droppings left by flies on white spot cards, he concluded that the bags, rather than repelling the flying annoyances, actually attracted more of them. Via lucahuter Via lucahuter

Now, it doesn't say that he put pennies in the water, the study only says zip-lock bags filled with water were used.

One theory suggests that the water repels flies because it scares them.

When the flies see themselves in the reflection of the water they see multiple giant versions of themselves and they don't like it.

That still doesn't explain what the pennies are all about though.


As you can see, the YouTube comments support the fact this trick actually works.

YouTube via MudRFunR
YouTube via MudRFunR


However, I did find some information that might make some good sense.

The water and the pennies create a prism that reflects colors, and also projects the image of the water.

Flies don't like water, and they don't like the colors given off from the pennies. Flies have compound eyes so the bags look like a giant body of water to them, therefore they leave.

For me, this trick worked like a charm. Has it worked for you?

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