Matt.e, hot tubs and PME

The other approach to reducing step voltage is to have the users feet effectively insulated to a degree from terra-firma - hot tubs surrounded by decking or installed in wooden floored sheds effectively achieve this already, the reason it is not recommended is that the degree of isolation achieved is hard to verify, and if the decking can be lifted and taken away, then what.. In substations the same effect is achieved by gravel that is free draining (think like railway ballast), for a barefoot environment that is not applicable. Damp concrete slabs laid without a damp proof membrane actually can be quite well earthed to the ground below - if you have ever measured the Ze of rebar in a cement sub floor or foundations, in the manner of Mr Ufer's electrode, even without the conductive cement additives, quite respectable earth resistances are possible.


Of course if there are lethal step voltages around a property due to PME that are nothing to do with the hot tub, then many non-electrical wet activities, like children playing in inflatable paddling pools and watering the garden in flip-flops also become dangerous, so any tingles should be reported and investigated as soon as possible.

The other approach to reducing step voltage is to have the users feet effectively insulated to a degree from terra-firma - hot tubs surrounded by decking or installed in wooden floored sheds effectively achieve this already, the reason it is not recommended is that the degree of isolation achieved is hard to verify, and if the decking can be lifted and taken away, then what.. In substations the same effect is achieved by gravel that is free draining (think like railway ballast), for a barefoot environment that is not applicable. Damp concrete slabs laid without a damp proof membrane actually can be quite well earthed to the ground below - if you have ever measured the Ze of rebar in a cement sub floor or foundations, in the manner of Mr Ufer's electrode, even without the conductive cement additives, quite respectable earth resistances are possible.


Of course if there are lethal step voltages around a property due to PME that are nothing to do with the hot tub, then many non-electrical wet activities, like children playing in inflatable paddling pools and watering the garden in flip-flops also become dangerous, so any tingles should be reported and investigated as soon as possible.