Started as a janitor in 1993. Worked my way up to Chief Engineer at a 200,000 sq ft Class A retail building, then Maintenance Director at a senior living community. I've done every job on a building's crew, from mopping the lobby at 5am to writing the capital budget. I know what every room sounds like at 3am.
How to use this site
Pick the symptom your building is showing you. Each diagnostic walks you through the same way a good doctor would: presenting symptom → history → exam → differential → diagnosis → treatment plan → prescription → when to call for help → prognosis.
If you don't know what to call the symptom yet, scroll the "Reading the vitals" panel below. Most house complaints map to one of the systems listed.
Reading the vitals — match the symptom to the system
Banging or knocking
Usually heating / plumbing — when the system fires up or shuts down.
Boiler knocking / water hammer → Furnace banging on startup → Water heater popping →Chirping or beeping
A detector is telling you something — low battery, end of life, or the real thing.
Smoke alarm chirping every 30 seconds → CO detector beeping with no CO →Grinding or whining
Rotating equipment under stress — bearings, motors, compressors going.
Heat pump grinding outside → AC compressor warning sounds →Tripping / hot to touch
Electrical system catching a fault you can't yet see.
GFCI keeps tripping → Breaker keeps tripping → Breaker hot to touch → Outlet warm to touch → Lights flickering →Smell — sewer, gas, electrical
Three different alarms. One requires you to leave the building immediately.
Sewer smell in the house → Drain gurgling sound →Doors / windows misbehaving
Structural canaries. The building is shifting under you.
Doors not closing, sticky windows →Fire extinguisher questions
Lifecycle decision — when to recharge, when to replace.
Replace vs recharge →HVAC misbehaving
Furnace won't start. AC blowing warm. Heat pump short-cycling.
Furnace won't ignite → AC blowing warm air → Heat pump short cycling → Furnace overheating →Plumbing problems
Toilet, drain, water heater, water pressure diagnostics.
Toilet keeps running → Toilet keeps clogging → Low water pressure (whole house) → Water heater leaking →Appliances + bills
Dryer takes forever. Electric bill suddenly high. Humid basement.
Dryer takes forever → Electric bill suddenly high → Humid basement →Buying guides & product reviews
When a diagnostic prescribes a specific tool or detector, the product gets its own dedicated review. No generic "10 best" listicles where every entry is "great." Here's what we've reviewed.
Life safety — smoke & CO
Detectors that protect the people in the building. Reviewed by an SFFD-certified Fire Safety Director.
Best smart smoke alarms 2026 → Kidde 21029778 review → Nest Protect alternatives →Electrical tools
The meters and testers a homeowner actually needs — picked by a 30-year IUOE Stationary Engineer.
Best home multimeters 2026 → Klein NCVT-3P review →Water damage prevention
Sensors and whole-house shutoffs that prevent the #2 homeowner claim category.
Flo by Moen review → Best water leak sensors 2026 →Automotive HVAC
When DIY is appropriate, when it'll wreck your compressor.
A/C Pro recharge kit review →HVAC — heating + cooling
Heat pumps, thermostats, humidifiers, dehumidifiers, AC units.
Best mini-split heat pumps 2026 → Best smart thermostats 2026 → Best whole-house humidifiers 2026 → Best dehumidifiers 2026 → Best portable AC units 2026 → Best window AC units 2026 → Best HVAC UV lights 2026 →Plumbing + water heaters
Tankless, heat pump, sump pumps, softeners, filters, cameras.
Best tankless water heaters 2026 → Best heat pump water heaters 2026 → Best sump pumps 2026 → Best smart water softeners 2026 → Best whole-house water filters 2026 → Best plumbing cameras 2026 → Best basement waterproofing 2026 →Electrical
Surge protectors, generators, tester kits, capacitors, igniters.
Best whole-house surge protectors 2026 → Best home generators 2026 → Best electrical tester kits 2026 → Best AC capacitor replacement 2026 → Best universal furnace igniters 2026 →Life-safety — combo alarms
Post-Nest-Protect smart smoke + CO combo picks. NFPA 72 placement.
Best smart smoke + CO combo alarms 2026 →Comparison guides — pick by use case
When two products solve the same problem differently, the comparison guides decide for you based on actual physics and economics — not marketing.
HVAC comparisons
Smart thermostat ecosystems, heat pump vs furnace, AC types.
Ecobee vs Nest vs Honeywell → Heat pump vs furnace cost →Plumbing comparisons
Tankless vs tank, condensing vs non-condensing, salt vs salt-free.
Tankless vs tank water heater → Condensing vs non-condensing tankless → Salt vs salt-free softener →Electrical comparisons
AFCI vs GFCI, Klein vs Fluke.
AFCI vs GFCI breakers → Klein vs Fluke multimeters →How-to guides — annual maintenance + emergency prep
The DIY procedures that prevent emergencies — annual descales, flushes, sensor cleans, vent cleans.
Annual maintenance
The 30-min jobs that extend equipment life by years.
How to flush a tankless water heater → How to clean an AC condenser coil → How to clean a furnace flame sensor → How to clean a dryer vent → How to bleed a radiator →Life-safety + emergency
Test monthly. Replace at 10 yrs. Know your shutoff.
How to test a smoke alarm → How to test a GFCI outlet → How to shut off water to your house →What makes this site different
- Doctor's voice, not blogger's voice. Every diagnosis walks the same nine steps a good GP would: symptom → history → exam → differential → diagnosis → treatment → prescription → when to escalate → prognosis. No "10 reasons why" listicles.
- 30 years on the actual floor. Every diagnostic is reviewed by someone who has been on his hands and knees in a mechanical room at 2am with the failure in front of him. Not a content writer who Googled it.
- The prescription tells you what to buy AND when not to. Affiliate links are clearly marked. When the math says "skip the DIY and call a pro," the page says that — even when the affiliate link below would benefit from the opposite.
- Tools and products get their own deep reviews. When a diagnostic prescribes a specific tool or detector, that product gets its own dedicated page (built out over the coming weeks). The patient gets the right tool, not a generic "best of" listicle.
This site uses medical vocabulary on purpose — triage, differential, prescription, prognosis, on-call. Diagnosing a building IS diagnostic medicine in structure. But Al is not a licensed physician. "Doctor" is a metaphor for the diagnostic voice. Full disclaimers.