After some advice: Mild tingle from shower when in use

[TheGovernor]

Hi all,

Just after some pointers please, I have an electrician via my Homecare agreement coming out tomorrow to have a look, as fiddling with electrics is well outside of my comfort zone.

Essentially, when the shower is in use I can feel a mild tingling when in contact with the metal collar of the hose and the main body of the shower - it's a gravity fed system, so no pump or electrics involved in powering the shower. This happens in both our en-suite and bathroom, only when in use and stood in the shower sopping wet.

Oddly, the tingling is more obvious if I have a cut on my hand or similar...

From what I can gather this sounds like a bad earth or neutral problem?

So, all I'm really after are any pointers in terms of what to tell him and what to look for when he's testing, I'm wary that he might dismiss the concern because it is quite subtle.

What kind of tests should I expect him to do, should he be using any specific test equipment?

I just generally like to have a feel for things to help protect myself against someone doing half a job, I've got no intention of trying to work this out myself.

Any help and advice that you can offer is greatly appreciated.

 

[ban-all-sheds]

it's a gravity fed system, so no pump or electrics involved in powering the shower.

But I bet there are some involved in heating the water.

Oddly, the tingling is more obvious if I have a cut on my hand or similar...

That's not odd.

Anywhere where you have sensitive nerve endings exposed would do the same. (Please don't try it to see how it feels)

I'm wary that he might dismiss the concern because it is quite subtle.

Tell him what you are experiencing - he should not dismiss it.

What kind of tests should I expect him to do, should he be using any specific test equipment?

He should be checking the presence and effectiveness of the supplementary bonding and checking for a voltage between the hose and the mixer.

If there's an immersion heater he should test that for leakage.

If there's an RCD on the immersion heater circuit he should check that it's working.

 

[TheGovernor]

it's a gravity fed system, so no pump or electrics involved in powering the shower.

But I bet there are some involved in heating the water.

It's all fed off a gas boiler, but of course the boiler needs electricity to work, which is I think what you might mean?

Oddly, the tingling is more obvious if I have a cut on my hand or similar...

That's not odd.

Anywhere where you have sensitive nerve endings exposed would do the same. (Please don't try it to see how it feels)

Yes, although having Googled a bit, I'm not the only person to have observed this for a similar set of symptoms...

I'm wary that he might dismiss the concern because it is quite subtle.

Tell him what you are experiencing - he should not dismiss it.

He/she may be fine, but you know what some tradesmen can be like (no offense intended to anyone!), I'm just concerned to give him enough info and in the right way that he has to do a proper investigation...

What kind of tests should I expect him to do, should he be using any specific test equipment?

He should be checking the presence and effectiveness of the supplementary bonding and checking for a voltage between the hose and the mixer.

If there's an immersion heater he should test that for leakage.

If there's an RCD on the immersion heater circuit he should check that it's working.

There is a immersion, although it hasn't been used ever really, so is switched off.

It's quite hard for me to get any closer to the fault because it'd be all trial and error, plus I'd be using my body as a test device, which probably isn't the most sensible thing to do!!

Saying that, I did get my wife to switch off the power to the upstairs lights and I swear it reduced (but didn't eliminate) the effect, it seemed to "tail off" just after the power was down, but not disappear completely. I'm almost loathe to offer that up, because I don't want to send him off on a wild goose chase for something so unscientific...

Thanks very much for your comments though, they are really appreciated, and electricity makes me nervous...

 

[bernardgreen]

First of all DO NOT USE THE SHOWER UNTIL IT HAS BEEN PROVEN SAFE

Any electric shock, fatal or just a tingle, to a human being requires two points of contact with the body and there must be a voltage difference between them.

In a shower there are two contact points mostly one is a hand and the other a hand or the feet. The shock or tingle will be strongest at the smaller of the two contact points. A finger is a small area of contact while a foot is a much larger area so the concentration of the current through the body is higher in the finger than in the foot . The higher the concentration the more sensation which means you are likely to feel it in the fingers but not in the feet.

So identify both contact points to assist the electrician to locate what is creating the voltage difference. Do it from memory and not by more experimenting in what is a suspect shower.

Are they shower trays or showers over baths ?

 

[TheGovernor]

They are both shower trays bernardgreen. I have only ever experienced the tingling when having a shower, i.e. stood in it soaking wet, so my feet are only in contact with the tray, which is plastic.

We also have a shower over the bath which is in the main bathroom, separate to the two I've already mentioned (it's a weird design my house and not half as grand as having three bathrooms sounds!!!), but I've not used this so can't say for certain whether it happens there too or not...

I'm hoping that whoever comes does look at it seriously, and is prepared to put the time in as I sense it won't be a five minute job!

If he just whips out a multimeter and tells me it's all fine, should that reassure me or concern me? Is there other test equipment he should use?

[Edit] I know neon-screwdrivers are generally frowned upon, but out of curiosity I just found that when the neon is touched to the shower it lights up, likewise to the taps in the sink, in fact to any tap etc in any bathroom... should I ignore this or does it add anything of value for the guy coming tomorrow?

 

[flameport]

If he just whips out a multimeter and tells me it's all fine, should that reassure me or concern me? Is there other test equipment he should use?

Concern - there is obviously some kind of fault, so if they just say 'all is well' they are lying.

 

[TheGovernor]

Thanks for the reply, I'm really grateful for any pointers at this stage.

I've been wracking my brains as you might imagine, wondering what might have triggered the problem. I then started to think that it has been happening a while and I'd just dismissed it as sore fingers (with it being so mild)..

I then remembered we'd had a new central heating pump fitted about a year ago, then remembered seeing something about pumps leaking to earth, so I'm wondering if that is a possible route. That's also on the lighting circuit as I recall, which might link my "test" to the pump...

 

[bernardgreen]

What you have said about the neon lighting up when it is touched onto a tap is worrying. It might be that your "earth" wire is not at true ground potential.

In that situation I would measure the voltage on the pipe work relative to true ground by using a ground ground rod. The maximum permissable voltage between the "earth" wire and true ground is 50 volts but in reality should be no more than a couple of volts.

If it is more than a few volts then there is a problem with the earthing system and all items connected to the "earth" wire are in fact not earthed and may be high enough in voltage to create the tingle you feel.

Do you have under floor electric heating ? A fault on that can give rise to the effects of tingle and neon driver lighting up on "earthed" pipework.

 

[TheGovernor]

Hi bernardgreen, no, no underfloor heating... if it was the whole earthing system for the house, any thoughts on how that becomes faulty over time?

While I noticed this a while ago, it hasn't been like this forever, would I be right in reading something about loads of rain affecting earthing points (of have I dreamt that?)?

 

[bernardgreen]

The "earth" wire in the installation is more accurately a CPC Circuit Protective Conductor and its function is to provide a way for faults to trip protective devices such as fuses MCBs or RCDs.

In days of old it was connected to earth ( as in ground ) using either a rod driven into the ground or via a wire coming to the house from the local electrical substation where there was ground rod.

For various reason this changed to use either a ground rod ( known as a TT supply ) or by using the Neutral wire from the sub station to carry both Neutral and Earth ( known generally as a PME supply ) The Neutral is connected to a ground rod as the substation.

If the Live and Neutral wires coming into you house were swopped then the "earthed" CPC would be at 230 volts above ground. This is not in itself dangerous provided there is no way someone inside the building can make contact with anything that is in any way connected to the ground outside. Birds can perch on 11,000 volt cables in perfect safety but get a massive shock if they touch anything else that has an electrical path to ground or one of the other wires.

Shower trays and baths can have paths to ground via the drain pipes. Even plastic pipes that have had waste water flowing through them have a poor quality ( High impedance ) path through them and this path may reach ground via the sewer pipes.

There is also capacitive coupling between the human body and the ground, the neon screw drivers rely on this coupling, that allows a small amount of current to flow if the person or screw driver touches a live wire.

 

[TheGovernor]

That's really interesting bernardgreen...

It prompts a few questions in my mind:

Our house is a 1997 build so would guess it is likely to be a TT supply?

That kind of implies we've always had this problem but I've not noticed it until relatively recently?

Or, possibly the grounding at the substation might be faulty, which means every house in the road has this problem?

I wonder how that could be fixed if either of the above are true?

I suppose my mind is moving towards trying to work out what could be the trigger for me suddenly noticing this (which is either anew fault, or my lack of observation of the fact it's always been like this).

Is the fact that when we turned off the upstairs lighting at the CU the effect diminished a red-herring? I kind of understand that of course we're running out of information without someone actually looking at it.

Hopefully the guy who comes this afternoon knows his onions and can either find a real fixable fault in the house, or can identify where the issue is so it can be resolved. Because this is via the Homecare agreement with British Gas, I'm now half expecting a "refusal to fix as it's a design fault".

 

[JohnD]

A 1997 house is very likely to have PME.

The neutral is connected to earth at many places, not just at the substation. PME stands for Protective Multiple Earth. It is unlikely to have become detatched at all of them.

It will also have been bonded to many metallic water pipes in your house and your neighbours, some of which may go into the ground (although this is not done with the intent of adding more earthing rods, it does have this effect, but you mustn't rely on it, because at any time the pipes might be replaced with plastic).

 

[TheGovernor]

A 1997 house is very likely to have PME.

The neutral is connected to earth at many places, not just at the substation. PME stands for Protective Multiple Earth. It is unlikely to have become detached at all of them.

Ah interesting, making it more likely to be an internal fault (assuming it is PME), bringing back into the frame the lighting circuit as a possible culprit (I realise we're into conjecture here, but it's useful to help me think through the possibilities

It will also have been bonded to many metallic water pipes in your house and your neighbours, some of which may go into the ground (although this is not done with the intent of adding more earthing rods, it does have this effect, but you mustn't rely on it, because at any time the pipes might be replaced with plastic).

Understood, thank you

 

[JohnD]

If you have PME there will (should) be a label saying so, adjacent to your meter.

 

[TheGovernor]

You're correct JohnD, there is a sticker that say PME Terminal in the meter box, so that answers one question.

Based on your previous post, that (to my simple mind!) makes the problem much more likely to be inside the house than related to the house itself not being properly earthed...?