electric shock from a cold water tap

gerardmshort

i our utility room i get a shock when the cold water flows

i live in a rural location

any ideas

meercat

https://www.boards.ie/discussion/2058231823/electric-shock-from-a-cold-water-tap

The earthing arrangements need to be checked in the whole house

Especially a loop impedance test.

a rec should be contacted ASAP

2011

There is more than one issue here. I wouldn’t leave this if I were you. Get a qualified electrician to check it out asap.

kirk.

Ya as above usually a combination of issues

Earthing arrangements unsatisfactory combined with a fault

May not necessarily be that either, get it investigated quickly

10-10-20

Beyond the excellent and very-much correct guidance provided above, one thing that I'll add is that you just need to consider whether this could be an electro-static discharge related shock rather than a shock in the mains-current sense. A static electric shock would normally have the characteristic 'snap' and associated instantaneous tingle, but would be a once-off event until you move your body/clothes/hair and re-touch the tap.

Some items of clothes and footwear (as well as hair-sprays and flooring) may induce the build-up of electric charge upon your body which is then dissipated as you touch a grounded device or surface. These situations would normally be made more noticeable in a warm and dry room as the accumulated voltage is increased in these situations.

To dissipate any possible the static build-up, touch the unpainted metal frame of another earthed device or appliance to see if the same discharge occurs.

Beyond this described scenario, the earthing needs to be checked out by a qualified person.

Antenna

The OP says it happens "when the cold water flows" so I take it that nothing is felt when putting hand on the tap before turning it on? That would rule out static discharge.

Maybe its just a vibration in the pipes when the water is flowing which is being perceived as a very mild AC shock?

Whatever the cause, it would be good to hear of any clarification, updates or resolution from the original poster, out of respect to everyone above who has taken the time to reply

kirk.

I'm not sure this scenario of shocks from flowing water is making a lot of sense to me

The usual scenario would be live metalwork or taps as the resistance of water in a length of pipe is high, unless there's electrical equipment close to the tap like an instantaneous heater or pump switching on which could cause flowing water to give a shock

Slightly Kwackers

A neon screwdriver strikes at 60V, any leakage would probably be above this, so borrow one or better still a Voltmeter.

Is the floor bare concrete? I was once in a yard when I felt a tingle from a control panel cabinets exterior. I dragged a nearby metal dustbin close to it and measured the Voltage between panel and bin, it turned out that there was over 100V between the panel and earth as the ground wire to the feed had corroded.

RCD's have been in common use for a very long time now, so if current was flowing to ground I would expect a trip event if it was in a "utility room".

A "back room, "box room" or "cow shed" might not have an RCD :-)

Anyway it would do no harm to hit the test button on any RCD's you have regardless.

kirk.

Voltmeter probably wouldn't tell him much unless he has a reference to earth like your example of the bin.

Phase testers can give a good indication alright.

If the pipework is plastic I'd say the chances of flowing water being live are low as resistance of water in 1/2" pipe is high per metre.If metal it's usually just live metalwork.

Op needs a REC anyhow to check the installation

2011

https://www.boards.ie/discussion/comment/118662605#Comment_118662605

These neon screwdrivers are notoriously unreliable which is why they are banned from many sites. They have been known to routinely provide false positives and false negatives. Any electrician worth their salt will use professional test equipment only.

As above this issue needs to be properly investigated by a qualified electrician.

2011

https://www.boards.ie/discussion/comment/118662646#Comment_118662646

A reference to earth is easily obtainable with a "wander lead". This is commonly used in a situation such as this.

kirk.

https://www.boards.ie/discussion/comment/118666291#Comment_118666291

Do you mean a wander lead connected to MET ? I wouldn't necessarily trust that in these situations .

kirk.

https://www.boards.ie/discussion/comment/118666288#Comment_118666288

Which is why I said ' indication '

I'm not advocating their use for testing or general use as they are a dated piece of electrical test equipment

kirk.

https://www.boards.ie/discussion/comment/118666288#Comment_118666288

This an advanced form of the phase tester

The single point contact tester , "Detects live panel casings"

Not advocating their use use either

https://www.amazon.co.uk/Martindale-VT7-Single-Voltage-Indicator/dp/B00PB25Y12/ref%3Dmp_s_a_1_3?crid=3TJTB0LN4K9CG&keywords=vt7+tester&qid=1645437124&sprefix=vt7%2Caps%2C195&sr=8-3

2011

https://www.boards.ie/discussion/comment/118666579#Comment_118666579

Why would you not trust such an established method?

The use of wander leads is a very standard and accepted practice throughout the electrical industry. A quick google will demonstrate this, here is just one example:

https://ciftraining.ie/wp-content/uploads/2020/11/Presentation-for-Download.pdf

https://www.boards.ie/discussion/comment/118666616#Comment_118666616

Fair enough. I just don't see the point in using an unreliable device for "indication".

How is it that you think that this £30 "advanced form of the phase tester" works without a proper refrence? This would not be considered professional test equipment. It belongs in the bin.

kirk.

What are you connecting the wander lead to ?

kirk.

A voltage test between the MET and metalwork is not a reliable method of detecting the presence of live metalwork as they may both be at the same potential in a fault condition

2011

FYI, on the instructions for the "advanced form of the phase tester" you are proposing it states:

3.3 Testing for the Presence of Voltage Warning Single pole phase testing is not suitable to determine if a circuit is not hazardous live. A double pole voltage test should always be used for that purpose.

See link:

https://docs.rs-online.com/ad40/0900766b8129a4c5.pdf

As can be seen even the manufacturer of the device yuo are endorsing states that "double pole voltage" is required.

https://www.boards.ie/discussion/comment/118667216#Comment_118667216

There are lots of places you could connect, the MET would be a good one to start with.

https://www.boards.ie/discussion/comment/118667242#Comment_118667242

If you verify that the MET, and all conductive parts are at the same voltage then there is no shock risk.

kirk.

https://www.boards.ie/discussion/comment/118667206#Comment_118667206

There's times when you don't want or have s reference

That's where the single point contact testing comes in

As said they're only indicators

2011

https://www.boards.ie/discussion/comment/118667368#Comment_118667368

Think about what you have written!

The risk only occurs when there is a potential difference between two simultaneously accessible points. Therefore it follows that if there is no reference there is no risk. This is why birds can safely land on MV and HV overhead lines. This is why safety isolating transformers are sometimes used i.e. the secondary side has no earth refrence.

In a domestic installation a reference can always be found.

I know you keep saying the above are "only indicators" but even the manufacturer undermines their own product! Avoid, avoid, avoid!

kirk.

https://www.boards.ie/discussion/comment/118667364#Comment_118667364

We are debating indication and testing , both have their uses here

I don't need to think about what I'm writing as I have a lot of experience troubleshooting faults

"If you verify that the MET, and all conductive parts are at the same voltage then there is no shock risk"

The above is totally wrong , think about neutral inversion and electrical shock from metalwork connected to MET

I have seen it many times where metalwork is live and at same potential as MET, that was my point as the fault may be local or otherwise

Gant21

The electricity could be carrying the current. Hot water is more conductive due to the molecules make up.

2011

https://www.boards.ie/discussion/comment/118667713#Comment_118667713

I don't want to turn this into a pi55ing contest, but I have a bit of experience too. You suggest an instrument to be used in a way that conflicts with what the manufacturer recommends. Then you say this is for "indication" only, in which case please state what you think it indicates.

Ok, I'm thinking about neutral inversion now explain to me why the voltage should not be measured between two points. If concerned about neutral inversion why not simply test to see if the neutral is grounded?

How exactly would you test for this once you had concluded your “indication only" test? 

kirk.

https://www.google.com/amp/s/martindale-electric.co.uk/product/vt7-single-pole-voltage-indicator/amp/

https://www.google.com/amp/s/martindale-electric.co.uk/product/vt7-single-pole-voltage-indicator/amp/

Not endorsing the product but as can be seen its used is described below

"The probe is GS38 compliant and is ideal for detecting live panel casings

kirk.

https://www.boards.ie/discussion/comment/118667803#Comment_118667803

I made my point and I'm not getting bogged down further

You said there is no shock risk if met and metalwork are at same potential and I pointed out your mistake

I have seen it happen many times where metalwork is live and at same potential as met

2011

https://www.boards.ie/discussion/comment/118667866#Comment_118667866

No I did not say that. My exact words from my unedited post (#18) above are "If you verify that the MET, and all conductive parts are at the same voltage then there is no shock risk." Pay particular attention to the part that I changed to bold in this post. A current will only flow between two points when there is a potential difference between them. Conductive parts are basically anything that can conduct.

No potential difference = no current will flow = no shock risk.

So it would seem that you believe that both the manufacture of the VT7 device and I are incorrect in our assertion that the "testing for the Presence of Voltage Warning Single pole phase testing is not suitable to determine if a circuit is not hazardous live. A double pole voltage test should always be used for that purpose."

I see that you do not want to get "bogged down" in stating how you would deal with test this.

Instead you misrepresent what I said (by ignoring "all conductive parts") and then state that I am incorrect!

https://www.boards.ie/discussion/comment/118667827#Comment_118667827

The thing about instructions / manuals and datasheets is that all of the text in them applies, not just the parts that you like. When dealing with a mains voltage installation it is not just unwise to ignore manufacturer's warnings it is potentially dangerous.

kirk.

You're still wrong 2011 can you not see ?

The MET and all conductive parts can be at the same potential and you can still receive a shock from either the MET or the conductive parts

Faults can be local or otherwise

My reasoning for mentioning single point indication is that 2-wire testing (either resistance or voltage can be misleading unless you know what you're doing)

For example all metalwork and CPCs locally may be live or the entire installation metalwork and MET may be live , in these cases wander leads may be misleading unless you know what you're doing

kirk.

I am only advocating single point testing as an indicator and no more

Other testing is still required

I can outline a test procedure here when I get time if you wish . A wander lead would probably form part of it.

I suppose you would also throw all non-comtact testers in the bin too as they are unreliable , even though they are an invaluable troubleshooting tool ??

2011

https://www.boards.ie/discussion/comment/118668359#Comment_118668359

What is single point testing an indicator of ??

So now that you finally acknowledge that a wander lead would "probably" be part of your conclusive test it would seem that we are on the same page.

Regarding the reliability of non contact testers I think this link says a lot:

https://www.reliableplant.com/Read/23450/Noncontact-electrical-tester-recalled#:~:text=Noncontact%20electrical%20tester%20recalled%20by%20Fluke%20due%20to%20shock%20or%20burn%20hazard,-RP%20news%20wires&text=Hazard%3A%20The%20testers%20can%20fail,electrical%20shock%20or%20thermal%20burns.

https://www.boards.ie/discussion/comment/118668335#Comment_118668335

How can you get a shock if everyhting is at the same potential? Let's think this through, all accessiable (this means everything that can be touched) conductive parts (anything that conducts) are at the same potential yet you think a current can flow?

The OP gets a shock when he/she touches the tap. That menas that something else they are in contact with is at a different potential. Do you agree? This is a yes / no question.

Regarding your "....can be misleading unless you know what you are doing" statement, I agree 100%. That is why in my very first post on this thread stated "Get a qualified electrician to check it out asap" as a person with this qualifiation should know what they are doing (post #3). This is not a DIY issue here. You will also see that I pointed out in the same post that there is more than one issue in this case.

Slightly Kwackers

https://www.boards.ie/discussion/comment/118666288#Comment_118666288

I never came across a site that banned their use. Personally I haven't used one for years, but they provide an indication of Voltage in excess of 60V without a problem. You need to adopt the practice of using a known source to check the thing before and after though.

Obviously an AP or SAP would be shown the door if he used one, but it does not mean that the device is useless. A neon lamp is governed by the laws of physics, just like a Fluke.

The reason for the neon, is that I was caught out once by a hot tap, It must have been turbulence, but I felt a 50Hz "tingle" from the water flowing from it. I thought it was odd as there was no sensation from the body. On checking it was dead.

As the topic relates to "home" I would assume that "professional" equipment isn't available, even if it was, it's capable of being misinterpreted as is the neon

buried

Don't know if this is of any use but I had the same problem about 15 years ago, this same thing was happening. I noticed that the exact same time it had occurred, a neighbour that lives a good 200 feet away from my house across the field installed a new outdoor light for his farmyard, and everytime that outdoor light was switched on, that's when I would receive a shock from the tap. I told the neighbour, and he ultimately fixed his light, he said it wasn't earthed by the guy he got to do the job. Never got a shock again from the tap.