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Every home is four machines wearing one brick coat: a machine that moves heat, a machine that moves water in and out, a machine that moves electricity, and a quiet set of defenses that keep water and soil gas where they belong. This page is the brief: one interactive cutaway of the whole house, then a short plain-English chapter on each system. When you want the whole story, every brief links to its full chapter: HVAC, plumbing, electrical, flooring, and the environmental hazards.
One cutaway, every system. Hover over or tap each part: orange is warm air, slate is return air, blue is water in, brown is water out, gray is electricity, purple is the radon system, and green is the water-defense team.
Hover over or tap each part. Orange = warm air out, slate = air back, blue = water in, brown = water out, purple = radon, green = water defense.
How it works. Water supply pipe has to hold city pressure around the clock, so its material is everything. Galvanized steel (standard here from about 1900 to the 1960s) is steel dipped in zinc; the zinc sacrifices itself to corrosion for a few decades, and then the steel rusts inward, narrowing the bore year by year until the top-floor shower is a dribble. Copper replaced it because copper barely corrodes in Chicago water, and the Chicago Plumbing Code keeps copper as the standard for drinking-water piping in the city today. Drainage is a different job with different physics: no pressure, just gravity, so the material question is longevity and quiet. Cast iron does 50 to 100 years and fails from the inside; PVC plastic is effectively immune to corrosion, and since the city's 2021 plumbing code amendments it is permitted for drains and sewers in residential buildings up to 60 feet, which took real money out of replacing dead cast iron runs.
Supply pipes are arteries under pressure; drains are the throat, working by gravity. Galvanized arteries clog with rust like cholesterol, copper ones basically do not, and Chicago requires the good arteries. For the throat, old cast iron eventually rusts through from the inside, and the modern fix is plastic, which the code now allows in houses and most flats. Quick home test: run the top-floor tub and flush a toilet. If the tub goes quiet, the arteries are telling you their age.
Code anchors: Chicago Plumbing Code (Municipal Code Title 18-29), water piping standards and the 2021 amendments expanding PVC drainage to residential buildings up to 60 feet. Full chapter: Chicago Plumbing, Explained.
How it works. A wire is metal wrapped in insulation, and the insulation is what ages. Wiring from before roughly the 1940s used rubber-and-cloth insulation that dries, cracks, and flakes off after a century, leaving bare conductors in the walls; knob-and-tube versions also lack any ground wire, the third path that gives escaped electricity somewhere safe to go. Modern wiring uses thermoplastic insulation rated for decades more heat, always includes a ground path, and in Chicago it all runs inside the metal conduit the city's electrical code has required for over a century. That conduit is the old homes' saving grace: because the pipes are permanent, an electrician can pull brand-new wire through the original conduit without opening a single wall.
Imagine an extension cord left in the sun for 100 years: the plastic goes stiff and crumbly. That is cloth wiring, and it is why insurers ask about it by name. Modern wire is the fresh cord, plus a third prong for safety. And Chicago buildings hide a gift: the wires live inside metal pipes, so replacing century-old wire is often more like restringing a necklace than remodeling a house.
Code anchors: Chicago Electrical Code (Municipal Code Title 14E), metal raceway requirement; Illinois Carbon Monoxide Alarm Detector Act for the alarm rules mentioned above. Full chapter: Chicago Electrical, Explained.
How it works. Waterproofing is a chain of defenses, in order of cheapness. First the roof and gutters collect the rain and the downspouts move it; extensions and splash blocks carry it clear of the foundation. Second, grading: soil sloped away (about six inches of fall in the first ten feet) so surface water never parks against the wall. Third, below ground, drain tile, perforated pipe alongside the footing (or retrofitted inside the slab edge), intercepts ground water before it can build hydrostatic pressure, and delivers it to the sump pit, where the pump ejects it away from the house. Exterior membrane waterproofing (excavating and sealing the outside of the wall) is the premium last resort. Sewer backups are a separate problem with separate equipment: a check valve, flood control system, or overhead sewer conversion keeps the city's combined sewer from visiting your basement during a cloudburst.
Umbrella, raincoat, boots. The umbrella is your roof and gutters, the raincoat is soil sloped away from the house, and the boots are the drain tile and sump pump for whatever gets through. Most wet basements are cured with the umbrella and the raincoat alone, which cost almost nothing. The pump is for the rest, and a battery backup matters because big storms like to take the power out right when the pump is needed most. Sewer backup protection is a different gadget for a different problem: it is a one-way door that keeps the city sewer from backing up into your floor drain.
Sump, ejector, and sewer work in Chicago runs through permits under the Chicago Plumbing Code (Title 18-29). Flood history is a written disclosure item in Illinois home sales.
How it works. Radon is an invisible, odorless radioactive gas created as uranium in the soil naturally decays. It drifts up through slab cracks, floor drains, and sump pits, and in an enclosed basement it can concentrate to levels that matter: it is the second-leading cause of lung cancer after smoking. Mitigation is called sub-slab depressurization and it is elegantly simple: a small pit is sealed into the slab, a pipe runs from it up through the house (or along the exterior) past a quiet inline fan, and out above the roof. The fan keeps the soil under the slab at a slightly lower pressure than the basement, so soil gas flows into the pipe and out the top instead of into the house. A U-shaped liquid gauge on the pipe, the manometer, shows the vacuum is alive.
A straw with a gentle fan, sipping air from under your basement floor 24 hours a day so the gas leaves by the roof instead of the rec room. The whole system uses about as much power as a light bulb. Testing during your inspection costs around $150, we've seen full systems run between $1,500 and $3,500+ installed depending on the home's size and the system's complexity, and the little U-gauge with offset liquid is the "working" light.
Illinois specifics: sellers provide radon disclosure under the Illinois Radon Awareness Act, mitigation professionals must be state licensed (IEMA-OHS), and since June 2013 the Radon Resistant Construction Act has required new Illinois homes to include passive radon piping, so newer homes often need only a fan added.
How it works. Chicago heats with one of two loops. A forced-air system loops air: the furnace warms it behind a sealed heat exchanger, the blower and ducts deliver it to the registers, the returns bring it back through the filter, and in summer a cold coil above the furnace borrows the same ducts to run central air. A boiler system loops water instead: the boiler warms it, pipes carry it to radiators in each room, and the metal quietly radiates the heat, which is why vintage buildings have no ducts and, usually, no built-in cooling. Behind the word "radiator" hide two different machines, steam and hot water, and telling them apart matters at inspection.
Forced air is a hair dryer with straws to every room; radiators are hot water bottles plumbed together. One filters and cools as a side effect, the other is silent and nearly immortal but sprouts window units every July. The full chapter walks the furnace loop, steam vs hot water boilers, how the AC condenser moves heat outdoors, and the service-life numbers your inspector can pin on each machine.
Full chapter: Chicago HVAC, Explained, including "ask your inspector to age the machinery".
Educational summary, not code advice or an inspection. Primary sources: the Municipal Code of Chicago (Titles 14E, 18-28, 18-29), the Illinois Radon Resistant Construction Act, and the Illinois Carbon Monoxide Alarm Detector Act.
We are real estate brokers. We are not masons, plumbers, electricians, structural engineers, architects, inspectors, or attorneys, and nothing on this page substitutes for any of them. These guides are our team's plain-English interpretation of Chicago's codes and of how local buildings behave, written to educate, and codes change and buildings surprise. Before money moves, put licensed professionals and the primary sources we link in front of your specific property. We are glad to recommend the pros we trust.
Send it over. We will tell you what era its machinery likely is, what to verify at inspection, and what each answer costs in this market.
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