Tap corrosion and 0.5V measured to house earth

[m4rcus]

Hi,

I've now got a second tap in the cloakroom sink that has corroded, yet another tap of the same style elsewhere in the house is okay. I've been able to measure 0.5V between the tap and the house earth (plug socket).

Any ideas as to what's going on?

Cheers,

M

 

[RF Lighting]

Cheap taps?

 

[m4rcus]

I did that that to begin with and got another tap from the supplier... same thing happened. The other same tap in the main bathroom has not had the same issue. Plus the voltage thing confuses me.

 

[RF Lighting]

I assume you are measuring with a high impedance volt meter? What made you want to carry out this test?

 

[ericmark]

The problem has been recorded with narrow boats for many years. The use of copper rather than iron earth rods can mean there is a current between copper and iron items.

Using sacrificial anodes of zinc can reduce the problem but use of diodes between earth electrode and boat seems to be the normal method to stop the electrolyse between the items.

 

[m4rcus]

Hi, I did forget to mention that the corrosion is the chrome plating lifting off.

I thought about trying it with a high impedance meter just to see if there was anything going on, which is when I found the 0.5V. The house is 30 years old, with a new consumer unit a year ago. It did it before the new CU and takes about a year to show.

 

[bernardgreen]

Where the "earth" wire runs parallel to a Live wire in twin and earth cable there will be a small voltage gradient induced along the "earth" wire and this is what you may be reading.

If the voltage "disappears" when a low impedance meter is use then the voltage is induced and does not pose any serious hazard.

If the voltage remains the same when measured with a low impedance meter ( or using a high impedance meter with a shunt load across the probes ) then the voltage is not induced and could indicate a problem with the earthing system.