My lights dim for a second when the AC or water pump kicks in — is that a problem?

Short answer: a brief, slight dim when a large motor (AC compressor, water pump) starts is usually NORMAL — motors pull a big inrush current for a split second as they start, which causes a momentary voltage drop, and the lights dip until it settles. It's physics, not a fault, IF it's slight, brief and not getting worse. It becomes a concern when the dimming is DEEP, long, worsening over time, or accompanied by flicker/buzz/warmth at a fitting or the board — those point to a loose connection, an undersized/overloaded circuit, or a wiring problem worth checking.

Normal (don't worry) if: - The dim is slight and momentary (a fraction of a second) right as the motor starts, then steady. - It's a big load doing it (AC, pump) — the bigger the motor's inrush, the more noticeable. - Nothing else is wrong (no burning smell, no warm fittings, no worsening).

Get it checked if: - The dimming is deep or lasts more than a moment, or is getting worse over time. - Lights on many circuits dip hard, or a specific circuit flickers. - There's any buzzing, warmth or a burning smell at a socket, switch, fitting or the distribution board — that's a loose/high-resistance connection, which is a real fault (and a fire risk), not normal inrush. - Sensitive electronics reset/reboot when it happens.

What's behind a bad case: a loose or corroded connection (higher resistance = bigger voltage drop + heat), an undersized cable/circuit for the load, or the motor lacking a proper soft-start. On a big AC/pump, a soft-starter reduces the inrush and the dip.

So: a gentle, brief dip on a big-motor start = normal; a deep/worsening dip, or any warmth/buzz/smell = get a licensed electrician to check the connections and circuit sizing before it becomes a bigger problem. Anyone's "harmless flicker" turn out to be a loose neutral?