Design procedure, products and reference for electrical designers
Water and installed wiring is a subject where the engineering judgement is unusually clear-cut and the field practice is unusually poor. The temptation after a flood is to get the lights back on. That order of operations is how people are killed.
A circuit that has been submerged cannot be cleared by looking at it. Water carries dissolved salts and silt into every enclosure it reaches, and the residue stays after the water has gone. It tracks across insulation, sits in the bottom of accessories and bridges terminals that appear perfectly dry.
Insulation resistance testing is the instrument that answers the question, not a visual check and not whether the breaker holds. Isolate at the origin, lock it off, and treat the installation as live until proven otherwise.
This is where an electrical programme meets a building one. Plaster, screed and timber hold water for weeks after a surface feels dry, and an installation certified in a wet building sits in moisture the day after you leave. The sequence is extraction, then structural drying measured with a meter, then electrical work. Contractors handling standing water removal in Orlando and comparable firms elsewhere own that first stage, and co-ordinating with them beats arriving to find the walls still saturated and the programme stalled.
Judgement on individual items follows the construction. Moulded-case devices, RCDs and anything with a sealed mechanism are replaced, because the internals cannot be inspected or cleaned and a contaminated mechanism may still operate once or twice before it stops operating at all.
Socket outlets, switches and junction boxes that were under water are replaced. The brass is cheap and the consequence of a corroded terminal is not.
Cable is more forgiving: PVC-sheathed cable that was wetted but is undamaged at its terminations is often serviceable. Cable with wetting inside the sheath, which means through a cut end or a damaged gland, is not, because water travels along the strands well beyond the point it entered.
Flexible cords, extension leads and anything with a moulded plug go in the skip.
Buried and concealed conductors corrode where they have been wet, particularly at clamps and at any dissimilar-metal joint. Continuity at the main earthing terminal and at every bonding connection is verified again, not assumed from the pre-flood certificate, because the protective conductor is the part that keeps every other defect from becoming an injury.
Write the readings down, name the items replaced and the items retained, and state the condition of the building at the time of testing.
A flood-damaged installation attracts questions years later, from insurers and from the next engineer. A set of recorded values at a known date answers them far better than anyone's memory.