# Baggies full of water to repel flies **URL:** \ **Category:** Factual Questions\ **Created:** [September 6, 2001, 2:37pm UTC](https://boards.straightdope.com/t/baggies-full-of-water-to-repel-flies/80034 "2001-09-06T14:37:00Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![justinh](https://avatars.discourse-cdn.com/v4/letter/j/9fc29f/32.png) [@justinh](https://boards.straightdope.com/u/justinh)\ **Post date:** [September 6, 2001, 2:37pm UTC](https://boards.straightdope.com/t/baggies-full-of-water-to-repel-flies/80034/1 "2001-09-06T14:37:00Z")
Has anyone heard of hanging baggies full of water around to repel flies? Seen it tried but don’t know the reasoning. “It just works” is what I hear. ---
**Author:** ![KCB615](https://avatars.discourse-cdn.com/v4/letter/k/ea666f/32.png) [@KCB615](https://boards.straightdope.com/u/KCB615)\ **Post date:** [September 6, 2001, 3:05pm UTC](https://boards.straightdope.com/t/baggies-full-of-water-to-repel-flies/80034/2 "2001-09-06T15:05:12Z")
It was tried in the 1700s, and didn’t work. There isn’t enough water inside the bag to knock down a fire that was big enough to burn/melt the bag open in the first place. Another tactic that was used was a barrel of water with a gunpowder charge to blow the end off of the barrel. As you can guess, that didn’t work either. Because these things didn’t work, in 1875 a piano factory owner in New Haven, CT invented the heat activated sprinkler head. Now you have the same heat activating qualities the bag of water has, and a large water supply backing up the sprinkler heads. Works so well that to date, there have never been multiple fire deaths in a properly sprinkled building. ---
**Author:** ![KCB615](https://avatars.discourse-cdn.com/v4/letter/k/ea666f/32.png) [@KCB615](https://boards.straightdope.com/u/KCB615)\ **Post date:** [September 6, 2001, 3:06pm UTC](https://boards.straightdope.com/t/baggies-full-of-water-to-repel-flies/80034/3 "2001-09-06T15:06:21Z")
Wait, am I bad. Flies. Not fires. Thats what I get for reading with my glasses off (droops head and walks away). ---
**Author:** ![manhattan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/manhattan/32/7_2.png) [@manhattan](https://boards.straightdope.com/u/manhattan)\ **Post date:** [September 6, 2001, 3:13pm UTC](https://boards.straightdope.com/t/baggies-full-of-water-to-repel-flies/80034/4 "2001-09-06T15:13:58Z")
**Jeremy** , only you (and possibly **Tomndebb** ) could make a goof of that magnitude and _still_ eradicate ignorance. The fact that those methods of fire supression were tried was unknown to me and probably others. Thanks. ---
**Author:** ![Ringo](https://avatars.discourse-cdn.com/v4/letter/r/779978/32.png) [@Ringo](https://boards.straightdope.com/u/Ringo)\ **Post date:** [September 6, 2001, 3:14pm UTC](https://boards.straightdope.com/t/baggies-full-of-water-to-repel-flies/80034/5 "2001-09-06T15:14:44Z")
When I asked this question once > [@](#): > > We just had lunch on the patio of a little restaurant. My partner noticed that there were baggies with water in them hanging from the tops of the pillars that support the tin roof. Now, maybe we’re the only two people who had never seen this before, but it was new to us. A fellow diner told us that the bags are there to keep flies away, and she swore that it works. Does this work? If so, how? [metroshane](http://boards.straightdope.com/sdmb/member.php?action=getinfo&userid=2782) said: > [@](#): > > i’m in texas and i have seen them in old bar-b-q houses, and i tried it. it seems to work but it may be phsychological. i’ve heard it’s because when lite passes through the bag, the reflection of the water makes it look as though water is everywhere, which flies don’t like, or something like that. also it’s supposed to only work if suspended with white string. And [Homer](http://boards.straightdope.com/sdmb/member.php?action=getinfo&userid=2534) said this: > [@](#): > > I worked at a BBQ place for three years and we always had problems with flies during the summer. The last summer I worked there, we did the whole baggie thing, and the number of flies did go down. May have been a bad year for flies, may have been psychological, but whatever it was, it seemed to work. And that was enough for the manager. ---
**Author:** ![Bumbazine](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bumbazine/32/362_2.png) [@Bumbazine](https://boards.straightdope.com/u/Bumbazine)\ **Post date:** [September 6, 2001, 8:22pm UTC](https://boards.straightdope.com/t/baggies-full-of-water-to-repel-flies/80034/6 "2001-09-06T20:22:32Z")
My SIL was telling us about this a couple of weeks ago. Apparently it works if there is a ceiling fan running in the room. The water in the bag will display a view (reflection?) of the moving blades of the fan and the flies think that there is something moving just over the doorway and won’t come through. I suppose the water would also show any other movement in the room as well. An interesting theory anyway. ---
**Author:** ![DMark](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@DMark](https://boards.straightdope.com/u/DMark)\ **Post date:** [September 6, 2001, 11:00pm UTC](https://boards.straightdope.com/t/baggies-full-of-water-to-repel-flies/80034/7 "2001-09-06T23:00:25Z")
> [@](#): > > \*Originally posted by KCB615 \* > \*\*Wait, am I bad. Flies. Not fires. Thats what I get for reading with my glasses off (droops head and walks away). \*\* don’t feel bad, dude…one of the threads below is “Consistant No Hitters” and I thought it said, “Consistant No Hitlers” and was wondering what in the hell that thread was about…someone sorry there ain’t been another good dictator in awhile? Needless to say, the baseball thread through me for a loop for a minute. I need a better monitor. back to the flies… ---
**Author:** ![starfish](https://avatars.discourse-cdn.com/v4/letter/s/87869e/32.png) [@starfish](https://boards.straightdope.com/u/starfish)\ **Post date:** [September 7, 2001, 2:15am UTC](https://boards.straightdope.com/t/baggies-full-of-water-to-repel-flies/80034/8 "2001-09-07T02:15:03Z")
> [@](#): > > \*Originally posted by beatle \* > \*\*When I asked this question once > > > [@](#): > > > > We just had lunch on the patio of a little restaurant. My partner noticed that there were baggies with water in them hanging from the tops of the pillars that support the tin roof. Now, maybe we’re the only two people who had never seen this before, but it was new to us. A fellow diner told us that the bags are there to keep flies away, and she swore that it works. Does this work? If so, how? > > \*\* A restaurant manager told me the bags of water were to keep birds from under the roof. The water refracts the light passing though. As a bird moves toward it, it makes it look like something is moving and the bird will veer away. This obviously will not work on birds which land in the parking lot, then fly in. It might help. It can’t work that well or everyplace would have them.