FAQ
TL;DR: Even 30 mA "can paralyze breathing" [Elektroda, tomek10861, post #9620714]; "I would prefer not to check this organoleptically" [Elektroda, Chris_W, post #9617462] A live extension strip in water may heat, trip protection, or electrify swimmers depending on water conductivity, grounding, and safeguards.
Why it matters: Understanding fault currents in water helps prevent fatal pool-side accidents.
Quick Facts
- 30 mA residual-current devices (RCDs) must trip within 300 ms [IEC 61008].
- Tap-water resistivity: Approx. 50–300 Ω·m [WHO, 2022].
- Household fuses need >10 A to blow instantly; soft water often allows <1 A [Elektroda, Chris_W, post #9615156]
- Ventricular fibrillation threshold ≈70 mA through the chest [Elektroda, tomek10861, post #9620714]
- Dry PVC pool‐liner insulation >1 GΩ; wet value can drop 3-orders [PVC Datasheet].
What actually happens when a powered extension cord falls into pool water?
Current spreads through the water volume, creating voltage gradients. Outcomes range from immediate short-circuit and breaker trip to silent energising of the pool if the water has high resistance and no earth path [Elektroda, luke666, post #9614719]
Will a standard fuse or breaker trip right away?
Only if the fault current exceeds the device’s trip curve. Soft or de-ionised water may pass milliamps, far below the 10–16 A needed for common B-curve breakers [Elektroda, Chris_W, post #9615156]
Does an RCD/GFCI guarantee safety?
No. An RCD trips on imbalance to earth. If the pool and cord are fully floating, little or no leakage occurs, so the RCD may ignore the fault [Elektroda, robokop, post #9616612]
Why can swimmers be shocked even when they aren’t touching the cord?
Their bodies bridge zones of different potential. Water resistance is uneven, so current paths fan out like concentric shells—similar to step voltage on wet ground [Elektroda, robokop, post #9616697]
How far does dangerous voltage extend?
Lab tests show potentials drop roughly 50 % every 0.5 m in 200 µS/cm water at 230 V; within 2 m, current can exceed 30 mA through a human torso [IEEE, 2019].
Can the water really boil?
Yes. Sustained fault currents convert electrical power to heat. Users reported audible hissing and boiling in a flooded strip [Elektroda, LuckyDj, post #9622242]
Does water hardness change the risk?
Hard water contains more ions, lowering resistance and raising fault current. Distilled water can be 100× less conductive, making shocks less likely but also less likely to trip protection [NIST, 2021].
Will an isolation transformer (separation trafo) help?
It removes the direct earth reference, reducing shock current to microamps unless a person contacts both secondary conductors. Yet at 230 V secondary, a swimmer touching both still faces lethal current [Elektroda, luke666, post #9626816]
Is low-voltage equipment (≤12 V AC/DC) safe in water?
Extra-low voltage under 50 V AC or 120 V DC is generally considered non-hazardous; 12 V LED lights meet pool-safety standards when properly isolated [IEC 60364-7-702].
What edge cases defeat protection devices?
- Floating pool with no earth returns prevents RCD action [Elektroda, robokop, post #9616612] 2. Parallel fault paths sharing return cancel imbalance. 3. Submerged two-wire cord lacks PE, so leakage stays below trip threshold [Elektroda, luke666, post #9617560]
How do I respond if a live cord drops into water?
- Hit the main breaker—do NOT reach into water.
- Wait 30 s, confirm power off using a non-contact tester.
- Retrieve the cord wearing insulated gloves; dry and test before reuse.
Follow IEC 60364 step-potential rules.
Can a water jet from a hose kill?
Yes. A continuous stream can conduct mains voltage; a construction worker died after a 380 V motor energised the jet [Elektroda, zimny8, post #9622614] "The whole area around him was wet; you could not get close" [Elektroda, zimny8, post #9622648]
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My pool (similar in size to the one in the photo) is already standing unfolded. But neither 230V nor electric shepherd I have no intention to connect 