Building systems, explained through their physics
Working simulations you can operate, for the homeowner with a problem and the technician who wants the numbers.
Water in the house
Supply pressure, hot water and drains.
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P-1
Why Your Well Pump Keeps Cycling: Pressure Tank and Switch
Run a well system, open the tap and match your symptom to the part that is failing, most often a tank that has lost its air.
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P-2
Why Your Water Heater Needs an Expansion Tank, and What PRVs Do
Watch house pressure climb while the heater reheats a closed system, and see what the expansion tank, the PRV and the relief valve each do.
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P-3
Water Heater Running Out, Popping or Lukewarm? What's Going On
Run a tank cut open, gas or electric, watch cold water rise under the hot while the shower runs, and trace popping, lukewarm or smelly water to a cause.
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P-4
Gurgling Drain or Sewer Smell? How Traps and Vents Work
Flush the toilet, block the roof vent and watch the suction at a sink's trap, in inches of water, until it pulls the water seal and lets sewer air through.
Heating & cooling
Refrigerant loops and the air they condition.
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M-1
How a Heat Pump or AC Works: The Refrigeration Cycle
Drag the room and outdoor temperatures, switch between cooling and heating, and follow the refrigerant round the loop and across a pressure–enthalpy chart.
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M-2
Interactive Psychrometric Chart, and How to Read It
Drag a point to read dry bulb, wet bulb, dew point, relative humidity, enthalpy and more at once, in SI or IP units, or learn the chart one family of lines at a time.
How these are made
Each explainer is built by an AI-assisted production system and checked before it goes live: an independent test suite, written from the published equations and reference values, tests every simulation, and every factual claim is checked against its source by a reviewer who did not write it. The pages explain mechanisms and diagnosis. They do not walk you through hazardous work on gas, refrigerant or line-voltage equipment, and they say when to call a licensed professional. More about how the physics is checked.