Which is safer/safest pump style in a garden 'splasher style' swimming pool?

note that in a full size swimming pool the pump is not submersible, but connected to the larger pool by a considerable length of pipe. The resistance of the water and the length to cross-section ratio means that in effect the water enters and leaves the pool in a way that there is no dangerous potential difference in the water. Similarly pool lights are firstly ELV and secondly enclosed in such a way that the light enters the water through a window from a sealed box with a light in it. Again, even if that box fills with water, and it is not really supposed to, the ability to induce a significant difference in voltage between any two points in the pool is very much limited.

Standards aside, a system where the voltage is in the water is lower, is likely to be safer, unless the construction quality in the lower voltage model is poorer as a consequence. However, as Graham notes the wet human  is a lot more vulnerable than a  dry one, and apparently innocent things like metal steps introducing a near earth voltage can become a hazard  during a fault if current paths have not carefully considered and eliminated. (simple measures like decking or plastic steps can raise the impedance of the fault loop to external ground)

However if the automatic disconnection in the form or RCD etc is working as intended, the risk is moderate, as you have to be in the water when the pump is on,  and in a place in the water where there is a significant voltage gradient, at the very moment  when a fault occurs. I'm sure plenty of folk ignore or forget the advice to unplug and live to swim another day, but the risk is not truly zero.

Mike.

edit PS
you might find this discussion of hand held electrode type baby bath heaters interesting - some of the thoughts are the same.

electrode type baby bath heater

It is amazing the difference between CE and safety mark parts of the world, and the rest.

Thanks. It is interesting you raise the point about potential for cheaper construction quality in a lower voltage model - this has been playing on my mind a lot - to the point while considering purchasing a DC pump, I was thinking perhaps I would need to buy a high watt rated LED SELV transformer because then I'd "know". The issue is you cannot see inside the transformer so you've no idea if there are any faults in the double insulation etc (or in fact if its a cheap knock off with key parts missing).

With the current filter pump (which is 'essentially' a submersible sitting in a sealed 2litre jug of water with two pipes attached), I did consider that if I were to earth the water inside by putting an electrode through the side, this might be a neat solution - but does rely on faith in the RCD and switching to TT to avoid spurious earth currents from PME.

Thanks. It is interesting you raise the point about potential for cheaper construction quality in a lower voltage model - this has been playing on my mind a lot - to the point while considering purchasing a DC pump, I was thinking perhaps I would need to buy a high watt rated LED SELV transformer because then I'd "know". The issue is you cannot see inside the transformer so you've no idea if there are any faults in the double insulation etc (or in fact if its a cheap knock off with key parts missing).

With the current filter pump (which is 'essentially' a submersible sitting in a sealed 2litre jug of water with two pipes attached), I did consider that if I were to earth the water inside by putting an electrode through the side, this might be a neat solution - but does rely on faith in the RCD and switching to TT to avoid spurious earth currents from PME.