Which fly is this, and what is it telling you?
You can sort these out from across a room once you know what to watch for, and the answer determines your entire plan. House flies are dull gray, roughly a quarter inch, and they land on food, counters, and skin. They come from garbage, pet waste, and manure outdoors. Little house flies are smaller and hover in open air, often circling in the middle of a room without settling anywhere. Drain flies look furry and mothlike, sit motionless on walls near plumbing, and fly in short weak hops when you disturb them. They live in pipe film. Phorid flies are the runners: they sprint across a surface before flying, and they signal something decaying and wet. Blow flies and flesh flies are the shiny metallic blues and greens, and they are the only group that means you should start searching immediately for a dead animal. In a Washington rowhouse this identification also tells you who owns the problem. House flies usually point outside to a shared alley container, while drain and phorid flies point inside, often to plumbing that serves more than your unit.
A month-by-month calendar for the District of Columbia
December through March, outdoor pressure is minimal. With winter lows averaging 28 degrees, house fly development stretches toward the slow end of the curve, and flies present in these months are coming from indoor sources: drains, wet potting soil, or a wall void. Some adults simply overwinter inside heated buildings. April and May bring a slow build. Material in bins and debris piles starts warming, pupae that overwintered in that debris finish, and the first outdoor flies appear around waste rather than in kitchens. June through September is the peak. Summer highs near 89 degrees and 66 percent humidity push generations through quickly, and this is when weekly trash discipline stops being optional. If your bin goes out every other week, you are producing flies faster than you remove them. October cools things off and pressure drops through November. This is the best month to clear debris piles, since that material is exactly where the next spring's pupae would otherwise spend the winter.
Alley bins and the block-level problem
This is the part of Washington fly control that no single household can solve alone. Attached housing with rear alleys puts many containers in one strip of pavement, often in partial shade, often with lids that no longer seal after years of collection trucks. What happens inside those containers is straightforward. Loose food waste at the bottom holds moisture, summer heat accelerates it, and the University of New Hampshire's figures apply: 75 to 150 eggs in a cluster, 350 to 900 per female over a lifetime, maggots hatching within a day. One container can supply a whole block. Adults fly between yards without difficulty, which is why treating only your own property produces disappointing results and why two neighbors can compare notes and reach opposite conclusions about whether a treatment worked. The workable move is collective. Agree on bagging everything, get failed lids replaced, rinse containers, and if the alley serves a mix of houses and small businesses, raise it with the business owners too. A provider surveying the block rather than one address will find this fast.
What a proper first inspection covers
Watch what happens in the first thirty minutes. If someone begins spraying before naming a source, you are buying a week. Outside, the walk should cover the alley container area including lid seams and the sludge at the bottom of each bin, any compost, the spot where a dog spends time, debris and clipping piles, and low ground that stays wet after Washington rain. Rear steps and areaways in older attached houses collect organic material and deserve a look. Inside, drains get tested individually with an overnight tape test rather than treated as a group. Someone should check under sinks for slow leaks, look at houseplant soil, and pull appliances if small flies concentrate in a kitchen. Basements with floor drains get particular attention. If metallic flies are present, the inspection extends to the attic, chimney, and soffits. Ask for a written finding: species, source location, corrective step, and follow-up date. Without that document you cannot meaningfully compare a second quote, because you will be comparing prices for unspecified work.
Renters, landlords, and shared plumbing stacks
In a divided Washington rowhouse or an older apartment building, a drain fly problem usually belongs to the building. Units connect to the same stack, so adults emerge from a fixture two floors away and end up in your bathroom, and your own scrubbing accomplishes nothing. Report it like a maintenance issue rather than a complaint. Name the exact fixture, give the date you first noticed flies, estimate how many appear and when, and include your tape test result if you ran one. Requesting drain line service gets a plumber or maintenance tech scheduled; reporting flies tends to produce a spray visit to your unit that changes nothing. Handle your own side first so the request is clean: brush your traps, keep trash bagged and out on the building's schedule, and stop overwatering plants. If the source is the shared alley container area or a common basement drain, say that specifically. Those belong to the owner, and in the District of Columbia's attached housing the shared elements are where these problems usually live.
Comparing two quotes without guessing
Set the quotes next to each other and look for a named source before you look at a price. A line that reads monthly fly service describes a subscription to adult knockdown. A line that reads brush and foam three drains, replace failed lid on rear container, reinspect in fourteen days describes a repair. Second, count visits. Drain biofilm regrows, so two to four weeks of dosing is normal, and Washington's four-month outdoor peak means a seasonal plan covers more ground than a one-time call. A cheaper quote is often cheaper because it includes less. Third, ask what each provider identified and how they know. If two companies name different species for the same problem, one of them did not look, and that matters more than the price gap. Fourth, get the retreat policy in writing, including whether a return trip inside the plan window costs extra. Finally, ask which parts you could do yourself. A provider willing to hand back the easy work is usually giving you the more honest number overall.