Shock off taps

I'd ask if the shock feels more like a "jolt" or more like a "buzz" ... the former might suggest static rather than mains?

I'd maybe try a voltmeter & long lead to a temporary electrode outside somewhere to the taps and various other exposed bits - just for a different viewpoint.

   - Andy.

aligarjon said:

I have taken an earth continuity reading from a socket to the kitchen tap pipework and am getting about 20 ohms. I don't know how accurate that is as the pipes are extremely difficult to access and appear to be painted. I cleaned them up as best I could but am literally only able to get the end of a tester prong on to it at a stretch as everything is behind the kitchen units. The taps are connected with flexi hoses.

What is the resistance from earth to the kitchen taps themselves please? Presumably, the flexi-hoses provide electrical continuity between the pipes and the taps. If they do not and the kitchen sink has supplementary bonding, that could be the link. Otherwise, if the taps are electrically isolated, a shock would not be possible.

Dry skin has a finite resistance: this would be lowered in the event of cuts and grazes. However, you might expect that wet hands (when turning the taps off) would also experience a tingle. In any event, some people might be more sensitive to a few mA than others.

Thanks Andy. I did mention static to her.  I get a lot of static shocks myself. Getting in and out the van. I had a  good one at Bristol Airport a few weeks ago with a metal hand rail. So once I get the shock I have discharged and I don't get a second one. Would the principle be the same here. Maybe ask her to touch it again after getting the first one and see .  

Gary

voltmeter & long lead to a temporary electrode outside

seconded - a connection to a TT earth that is not at the same potential as the flagstones (how good is the dampcourse ?) may imply something rather unpleasant is happening. Are there other properties on the same substation or pole transformer that are PME and may be also connected to a metal water main ?

If its a farm is there an electric fence in operation that may be introducing some bounce to the earthing systems ?

Shocks though wet and or damaged skin can be detected at far lower voltages than a dry skin contact, and could bu because of voltage offsets of a few volts - consider the classic 9v battery vs tongue as an example.

The 'electrode outside' could just be a garden fork or a long uninsulated screwdriver or similar. Readings of much more than single figure volts RMS should be investigated.

IT may be nothing but sustained and repeatable 'tingles' may be an early warning of something very bad indeed. Let us know how you get on.

Mike

I have discharged and I don't get a second one.

yes, or to make initial contact via something that limits the current - slightly damp wood or cloth or if you have one, a resistor of a few 'megs' - it is likely to be worse in bare feet it it is mains derived, or worse in insulating footwear if it is 'stat'.

Mike

aligarjon said:

I did mention static to her.

aligarjon said:

So once I get the shock I have discharged

So static should be brief, but tingles more prolonged. Save that, perhaps, first contact discharges a capacitor of some sort. Mike, over to you.

Hi Chris. The resistance at the taps was a lot higher, 150ohms plus. I wasn't convinced how good my probe connection was up there either which is why I tried the pipes below and noticed the flexi hoses.

Gary

150 ohms will not limit a shock current very much, it may mean there is a very small gap in the electrical contact with a watery fill across a thin washer or sealing compound of something. 

A multimeter AC volts to a concrete or tiled floor can be measured using a suitable bundle of salt water damp cloth with a bare wire or metal foil in the bundle as an 'artificial bare foot' contact. Not sensible on carpet or wooden laminates or anything else with a finish that wont like the damp of course ;-) 

Was the rod test (34 ohms) a Zs to the rod , or a prongs in the ground type test electrode tester, and were all other rod connections removed during the test ?

Mike

Hi Mike

The rod test was taken as a zs test at the CU with the cable disconnected from the CU. 

There were no parallel paths .  I could see the cable leave the CU and down the external wall to the rod.

I have asked to speak to the tenant again as I don't currently have a contact number for her

Gary

gets occasional shocks off kitchen taps and shower

Other thing to ask ... what else where they touching at the time?  If it's a mains shock there must be a circuit and it's possible the "other" contact is the live bit, rather than the taps. Things like "live walls" aren't unknown and things like C-stud partitions or even foil backed plasterboard can spread the voltage a long way from the fault. Resistances can conspire to make a shock painful without the current being quite enough to trip a 30mA RCD.

   - Andy.