I see your point, a nail through a cable can take out the 5 amp 1-minute delay RCD with the 30 mA 40 mS I have seen that happen, but in the main, water is the cause, and it slowly gets worse, so we see using an approx x3 between RCD's the 10, 30, 100, 300, 1amp and 5 amp does in the main give...