Live bath taps

[jtaunton]

The plughole must have some metallic element and be connected to something, otherwise you wouldn't be able to measure a voltage between it and something else, but if I have got this straight......

The taps are usually insulated (i.e the last set of piping to them is plastic) and if you drain them of water, there is not voltage between the plughole and the taps. If you turn back on the water supply, you then get a voltage, so it seems as if the water is acting as a conductor.

Could your pipes have inadvertently been bonded to neutral and the plughole to earth ? Use a long wander lead to check between a known earth (at the CU) and taps, plughole for resistance and voltage.

 

[Killemall]

AC or DC?

 

[mapj1]

The more I hear the less I like.
OK, either your plastic waste pipe or overflow pipe is not self draining and is really full of dirty water up to the point where it joins something metallically connected to something else, or there is a connection to the underside of your bath you do not yet know about, that 'connects' to the water. No handles or feet on this bath are there? or could it leak onto cables feeding an electric shower. or similar
We know that the when the link hoses between taps and the metal supply pipe is full, this is not at the same voltage as the bath waste.
Noddy solution is to link the taps to the first bit of metal on the waste pipe but thats not a real fix unless we know where its coming from.

TNC-S (aka PME -yuk, personally I don't like it for the reason to follow) means your neutral and earth will be at the same potential as each other, being conected at the meter board, but that when there is much load connected, this voltage is no longer the same as that of true earth, and pipes that go outside, such as metal waste pipes and gas and water mains, unless strapped to the main wiring earth, will appear to be 'live' relative to the wiring earth - in reality it is the otherway round of course, but the shock feels the same.
Also more insidiously, if you (or your neightbours) supply neutral drops off or goes high resistance, the earthing will be asked to carry the full house load current, until the fault is rectified, which as the fault is otherwise symptom less could be a long time, but all 'earthed' objects indoors become slightly live. (the symptom is a drop in supply voltage, but if youtr earth goes to the same water main as a neighbours, and they have PME too, then that water pipe will be the 100A bridge, so the voltage change is only tens of volts. BUT with that fault, changing the stop tap is lethal.)

Is there any chance of testing relative to an earth that is really 'terra firma'

Did you get anywhere with isolating the supply to sub-circuits one at a time by circuit and seeing if the reading drops or disappears?

 

[gazza30]

Hi Mike
I have checked all of the circuits one by one and there is no difference on the taps.
i tried turning them all off and then on one by one and with each one i turned on check the voltage od the taps.
But to go one better than that if i disconnect the earth bonding link from the consumer unit the voltage is the same also.
I put the earth bonding link back and disconnected the bonding on the taps (the first bonded item in the bathroom) put a volt meter between the plug hole and the earth bond and there was no voltage showing but still showing at the tap.
any more ideas
Is it a good idea to try an earth rod in the ground and bond the bathroom from that or will this be a waste of time?.
the plug hole on the bath is crome like plastic.

 

[andy]

Hi Mike
I have checked all of the circuits one by one and there is no difference on the taps.
i tried turning them all off and then on one by one and with each one i turned on check the voltage od the taps.
But to go one better than that if i disconnect the earth bonding link from the consumer unit the voltage is the same also.
I put the earth bonding link back and disconnected the bonding on the taps (the first bonded item in the bathroom) put a volt meter between the plug hole and the earth bond and there was no voltage showing but still showing at the tap.
any more ideas
Is it a good idea to try an earth rod in the ground and bond the bathroom from that or will this be a waste of time?.
the plug hole on the bath is crome like plastic.

have you checked that the bonding to the bathroom from the MET is not broken?

 

[Adam_151]

I don't suppose you own a clamp meter do you?, gazza30.

Some readings with one of them would be useful to check for things map has said about

 

[gazza30]

Andrew the bonding is complete as i can check it baqck to the cu
adam sorry i do not have a clamp meter

 

[kendor]

it is the taps because if i sut the water off and disconnect the taps and drain the water from the pipes and then test there is no voltage present.
my sink taps and the water inlet for the toilet are doing the same thing but the problem is only in the bathroom.
p.s the plug hole on the bath is also plastic.

Now what does that point to? Water introducing a hazard?

 

[mapj1]

tried turning them all off and then on one by one and with each one i turned on check the voltage od the taps.

I'm puzzled. Well, if even with them all off you STILL get a voltage in the bath OK, its not your electrics. If all off = no voltage, but voltage appears with any one circuit on, but makes no odds which one, even if its just the light circuit with no bulbs in the house lit, then there is something very odd. We need to know the voltage between terra firma and the PME earth at the meter board. I have a horrible feeling the whole house is floating away from true earth, and there may be a neutral- earth fault curent flowing to compensate.
How much of your plumbing is shared with the neighbours, and how much of the waste pipe is plastic before it reaches something metal that goes into the ground outside? - could it all be wet inside?
delay as was away at weekend - bac on ball now!

 

[gazza30]

Hi Mike
Hope you had a good weekend.
Now then none of the plumbing is shared with the neighbours the plastic waste from the bathroom goes through the wall to a drain outside but the plastic does not touch the water.
I will check the earth as you asked tomorrow and let you know the result.

thanks

Gary

 

[andy]

bacon ball now!

mmmmmm...... bacon mmmmmmmmmmmmm

 

[gazza30]

bacon ball ??????????????????????????????????????????????

 

[gazza30]

I have checked the earth at the cu there is an earth wire to the electric meter and one to the gas meter and the earth bonding circuit all of the other earth wires are from the house electrical circuits is this right?.

 

[securespark]

cosh

The problem with water is that the more pure it is, the more it is inclined to pick up impurities, IYKWIM.

Didn't see page 2, talk about being on the ball.....Doh!!

(The bacon ball, that is!)

 

[Damocles]

You have copper water pipes? If the pipes are copper then the taps will be at the same voltage as the pipes. If there is direct metal contact this is obvious, but if there is a plastic flexible connector it is less obvious and via the water. No water, no connection.

Even though you can feel a shock it does not necessarily mean it is dangerous, or that water conducts. You are not dead. Everything conducts to some extent, just a question of how much. Dirty water conducts more than plastic, quite a bit less than metal.

If you are measuring things with a digital voltmeter which has an input impedance of several Mohm it can read a voltage difference betwen essentially insulated conductors. If you connected a 100M resistor between live and an isolated tap, and a second 10M resistor between tap and earth you would get about 24V on the tap. Could measure it with the digital meter, and the tap would be safe. Might be able to feel it if you were all wet and grabbed the tap with one hand and the earth with the other.


This does not explain where you are getting a source of things at different voltages. Is it possible that there is a true independant earth being introduced somewhere? Metal bath? Steelwork in the building? Metal drainpie outside or at the loo? metal overflow? Any cables nearby which might somehow be inducing a voltage in your bath water? Plastic pipe fittings splitting conductive sections which are supposed to be bonded. Compression fiittings made up with ptfe tape everywhere insulating the sections. metal pushfit with platic spacers?

Is that main stop tap bonded back to the meter and you are quite sure it is bonded directly to the rest of the bathroom pipework?