Warm weather brings flies, and with them a steady stream of folk remedies. One of the oldest is the plastic bag filled with water and a few copper pennies, hung in doorways and on patios on the theory that reflected light confuses a fly’s compound eyes. Pest control professionals do not buy it. An entomologist who studies fly behavior says there is no evidence the trick changes fly activity at all, and the bag may work against you: condensation on the plastic draws thirsty flies, and any leak creates a fresh moisture source near the doorway.
The same water that attracts flies also carries minerals, sediment, and taste problems inside the house. Knowing whether a water softener improves your drinking water is part of managing the supply properly, along with understanding hardness, pH, and how much water the household actually uses.
Why the Penny Bag Trick Fails
The theory behind the trick sounds plausible: light refracts through water and off copper, producing flickers that overwhelm a fly’s vision. Entomologists point out that flies rely on many cues, including scent, warmth, and carbon dioxide, and a stationary bag provides none of these deterrents. Meanwhile, it provides something flies actively seek: water.
What the Evidence Shows
- No published study links water bags to reduced fly counts around homes.
- Condensation on the bag surface is a drinkable water source for flies.
- Leaks and drips keep soil and decking damp, which attracts more insects.
- A hanging bag can catch sunlight and draw attention from flies in the area.
Moisture Is the Real Magnet
Flies need water to survive and breed. Any persistent moisture, from a pet bowl to a leaky hose bib, becomes a gathering point. Understanding hard water and gray water quality helps homeowners spot the mineral deposits and damp zones that encourage insect activity around the house.
House flies breed in decaying organic matter, and a single female can lay several hundred eggs over an adult life that typically lasts 15 to 30 days. Warm weather shortens the egg-to-adult cycle to about a week, so a neglected compost pile or pet area can produce new flies faster than any repellent removes them. That biology is why moisture control and sanitation outrank optical tricks in every field test.
What Actually Repels Flies
Entomologists recommend a short list of methods with real evidence behind them. DEET-based repellents work on biting flies and mosquitoes. Eucalyptus and citronella scents repel some species for short periods. Screens, fans, and traps handle the rest mechanically. The list is short because most products sold as fly repellents have never been tested against house flies; the ones that work either mask the scents that attract flies or block physical access.
Sanitation Comes First
- Take out trash daily and keep lids sealed.
- Remove pet waste from the yard within a day or two.
- Rinse recyclables before storage.
- Compost kitchen scraps in a covered bin or bury them.
- Clean spills promptly, especially sugary drinks on patios and counters.
Repellents and Barriers
Citronella candles and eucalyptus sprays mask the scents that draw flies, but they work best as a supplement to cleaning, not a replacement. Home improvement writers have also tested the bag with pennies method indoors and reached the same verdict as the entomologists: cleanup beats optical tricks.
Choosing a Repellent
For outdoor dining areas, DEET products at 10 to 30 percent concentration give hours of protection against biting flies. For a fragrance-only approach, citronella and eucalyptus offer shorter, milder coverage. Either way, keep food covered and surfaces wiped.
Physical Barriers and Traps
- Install 16-mesh screens on windows and doors.
- Use ceiling fans or patio fans to make landing difficult.
- Set sticky traps and baited jar traps away from dining areas.
- Keep doors closed or use spring closures during peak fly hours.
Traps and fans do not remove the source of the problem, but they cut the number of flies that reach food. A combination of screens, fans, and daily cleanup keeps most homes fly-free without any chemical products at all.
Moisture, Pests, and Water in the Landscape
The yard is where most fly problems start. Standing water in saucers, clogged gutters, low spots, and overflowing birdbaths all support insect breeding. Fixing drainage removes the breeding ground faster than any repellent.
Outdoor Water Management
- Empty plant saucers after rain or irrigation.
- Clean gutters twice a year and extend downspouts away from foundations.
- Level low spots that hold puddles for more than a day.
- Change birdbath water every few days.
Timing irrigation matters as much as volume. Early-morning watering lets foliage dry before evening, and drip lines deliver water to roots instead of spraying into the air. Gray water from laundry and sinks can irrigate ornamentals, but it should be applied below the soil surface and never stored, because standing gray water becomes a breeding pool for insects.
Outdoors, water conservation landscaping reduces runoff and eliminates the soggy corners where flies breed, while keeping ornamental beds healthy on less water.
Heating and Delivering Household Water
Once water quality is handled, delivery matters. Tank-style heaters store 40 to 80 gallons and reheat around the clock, while tankless units heat water on demand and skip standby losses entirely.
| Heater type | Capacity | Efficiency | Lifespan | Best for |
|---|---|---|---|---|
| Conventional tank | 40 to 80 gallons | 60 to 70 percent | 10 to 15 years | Low first cost |
| Tankless | On demand | 94 to 98 percent | 20 years | Homes with high hot water use |
| Heat pump | 40 to 80 gallons | Up to 300 percent | 10 to 15 years | Warm basements, mild climates |
Gas-fired instantaneous hot water systems deliver 2 to 5 gallons per minute, enough for one or two simultaneous showers, and they earn back their higher price through lower standby losses.
Recirculation pumps keep hot water waiting at the tap, which cuts the time spent running cold water down the drain. Pipe insulation slows heat loss between the heater and the fixtures. For a family of four, a 50-gallon tank or a tankless unit rated near 8 gallons per minute at a 70-degree rise covers the morning shower rush without running out.
Estimating Household Water Demand
The average American home uses about 82 gallons per person per day indoors, according to EPA WaterSense estimates. Showers, toilets, faucets, and laundry account for the largest share, and the numbers drive both water heater sizing and supply pipe design.
Average Use by Fixture
- Shower: 2.0 to 2.5 gallons per minute.
- Toilet: 1.28 to 1.6 gallons per flush for modern models.
- Bathroom faucet: 1.5 to 2.2 gallons per minute.
- Clothes washer: 15 to 40 gallons per load.
- Dishwasher: 3 to 7 gallons per load.
Sizing calculations for water demand in a water supply system start with these per-fixture numbers, then apply a diversity factor so pipes are not oversized for simultaneous use.
Peak demand rarely equals the sum of every fixture. A typical morning rush with two showers, one toilet flush, and a running faucet pulls about 8 to 10 gallons per minute for a few minutes, and supply piping is sized for that peak rather than for every fixture running at once. Street pressure, usually 40 to 60 psi, also shapes what the system can deliver.
Testing and Monitoring Home Water Quality
A basic water test covers pH, hardness, total dissolved solids, and chlorine, with extra checks for iron, lead, and bacteria when the source is a private well. Test strips give a quick read, while certified labs provide precise results for a few dozen dollars.
Reading the Results
- pH between 6.5 and 8.5 meets the EPA secondary drinking water standard.
- Hardness below 60 mg/L is soft; above 180 mg/L is very hard.
- Total dissolved solids above 500 mg/L may affect taste and scaling.
Test more often after changes: a new water heater, a well repair, or a shift in taste or staining. Iron above 0.3 mg/L stains laundry and fixtures, and hydrogen sulfide gives water a rotten-egg smell that aeration or filtration corrects. Catching these problems early keeps them out of pipes, fixtures, and appliances.
A Simple Testing Routine
- Collect a cold tap sample in a clean glass jar after the water has run for a minute.
- Run a test strip for pH, hardness, and total dissolved solids, or send the sample to a certified lab.
- Compare the readings against the EPA secondary standards.
- Treat problems at the source, then retest after the treatment system is installed.
The methods of determining the pH of water range from color-change strips to handheld meters, and a single annual test catches most problems before they stain fixtures or affect equipment.