What should I do before the technician arrives?

For plumbing: if water is moving, the main shutoff is your best friend — usually at the meter near the street or where the service line enters the house. Closing it converts an emergency into an appointment. For anything less urgent, clearing the cabinet under a sink or the space around a water heater means the tech spends time diagnosing instead of moving your storage bins.

For cooling and heating: if you saw ice on the AC lines, shut the system off so the coil thaws before arrival — a frozen system hides the readings we need. Note the thermostat behavior, any breaker trips, when the filter was last changed, and what the equipment sounds like when it misbehaves. Intermittent problems especially benefit from a phone video of the misbehavior, because equipment loves to perform perfectly the moment a technician walks in.

For everything: the recent-history question matters more than people think. 'It started after the storm,' 'we just had the roof done,' 'it only happens on laundry day' — these sentences regularly cut diagnostic time in half. Write down what you have noticed and when it started; dispatch passes it to the tech before the doorbell rings.