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What happens if I find building wires submerged in water?

14 August 2017

Have you ever come across a flooded section of a house containing building wire and wondered what to do? 

Well it’s something our technical team often gets asked about, so we thought we’d provide a short guide. 

Firstly, it is important to isolate the installation from the mains supply before attempting to check or repair flooded cables. For obvious reasons, the sooner the flood recedes and action is taken the more likely it is that the cables will not be adversely affected. 

We can tell you that there is a good history for cable reuse if the flood has receded within one or two days and the water is uncontaminated – that’s important. In this situation, we believe there will be little detrimental effect to the cable.

Longer periods of submersion, or where the water is contaminated with chemicals, or effluent may be more problematic. 

What to do after the flooding has subsided
Where flooding has occurred and then receded, open all sockets, junction boxes, switches, ceiling roses and any other terminations to allow trapped water to drain. Remove conductor ends from terminals to allow inspection, cleaning and drying. Where possible wipe the cable surfaces to remove silt and to dry them. It may also be possible to use portable air-blowers to speed up drying. 

Of course, the time to dry indoor installations will vary depending on the prevailing ambient conditions of temperature, humidity and ventilation. The sooner drying and cleaning is achieved the less harm is likely to have been caused. 

After cleaning and drying has been completed it is recommended that a full installation test to BS7671 (IEE Wiring Regulations) is carried out to the standard required on a new installation.

What if the water is contaminated? 
If the flood water is contaminated, then there is a possibility of long term effects on the cable, including corrosion, environmental stress cracking and premature aging. The risk involved is difficult to quantify and whether the circuits are replaced or not may well involve considerations of the importance of the circuit and the consequences of a premature failure. 

Note: A quick and relatively useful indication of contamination of the flood water may be to test for pH to determine its level of acidity/alkalinity.

Please note that this guidance should not be used to contradict any proposed course of action given by consultants or insurance company assessors who will be better placed to comment on specific cases. 


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