Water In The Wires

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I have a problem with one of my downstairs socket circuits. When it rains for a long period (eg in July!), the circuit sometimes (but not always) trips. It seems obvious to me that water is getting in somewhere. My thought about solving this is to find out which bit of the circuit is causing the problem and then replace it. 

Seems to me that the simple way to do this is:

Turn off the circuit at the consumer unit. 

Work out the layout of the circuit using a multimeter. I assume it's a ring circuit but could be spurs.

Bypass each section of the circuit in turn with cable and narrow down which one seems to be causing the problem - i.e. see which one seems to stop the rain/tripping sequence. 

This could be time-consuming, but apart from that, is there anything against doing it this way?

Is there a better way? Could I measure the resistance between live and earth for each section, for example?

Thanks. 

 
+1 to the above.

It's more likely condensation rather than water ingress as such.

But does the affected circuit feed anything outside at all?

 
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Thanks - as far as I can see, that is basically something that measures resistance, but up to higher resistances than a standard multimeter? So if I use my normal multimeter, which goes up to 2M ohm, and find anything less than that in one part of the circuit, then I've probably found the culprit? 

 
You could start by simply removing the sockets from the walls and seeing if there is any evidence of moisture ingress - rust, damp..... but unless you've got proper test kit you could well be wasting your time.

Do you have any electrics in the garden off the downstairs socket circuit?

 
The problem with a normal multimeter us that it is simply unable to put enough current or voltage through the wires, therefore it will not show up any faults as such.

an MFT can put as much as 1000volts down the cable at perhaps 10amps,  

 
Last edited by a moderator:
Thanks - as far as I can see, that is basically something that measures resistance, but up to higher resistances than a standard multimeter? So if I use my normal multimeter, which goes up to 2M ohm, and find anything less than that in one part of the circuit, then I've probably found the culprit? 
Welcome to the forum, a normal multimeter is unlikely to perform a suitable test to identify your problem.

Doc H.

 
Once found a fault under downstairs floorboards, when it rained junction boxes laying on the dirt below were being drowned. Had been rewired by throwing cable from one side of the room to other, with junction boxes everywhere for good measure just thrown down on the floor.

 
reminds me of a place we went to during the month of horrendous rain and gales last winter. Lifted floorboards to find a foot of water and old VIR cables....

 
No the circuit doesn't supply anything outside, but I think it has been adapted from an old circuit that used to go to a slightly leaky conservatory. So there may be old parts of the circuit that are still subject to water ingress. The fact that heavy rain causes the problem does suggest this, rather than condensation - but, as is obvious, I am no expert. 

 
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