As stated below, its what is dissolved in the water that determines the level of conductivity. I used to work on old overhead cranes with variable speed control that had a tub containing a water/salt solution and a moving contact that was lowered in and out of the solution to form a 'variable resistor' to control the crane speed. The crane drivers used to mix their own solution up to how they liked the response of the controls. If there wasn't enough salt though, the crane would be very slow or not move at all.
Talk about coincident. I recently watched an urban explorer video in a Welsh Slate Mine. They were using Three such buckets for controlling the winches. www.youtube.com/@IKS-Exploration Abandoned Slate Mine.
@@G1ZQCArtwork Very interesting. I could not make out all the details of the installation. The ones I worked on had a second contact out of the tub, so the circuit was made from the moving contact through the solution into the tub contact. Certainly some examples of wound rotor motors to be seen there. Thanks for the link.
@@three-phase562 These mechanisms also served as a resistor for slow start for big motors, to get them to start moving before applying the full load. Quite dangerous in an enclosed space, the gasses given off are Hydrogen & Oxygen. BOOM. Its done today by switching coils.
Inconclusive. What.!? Water is a very poor conductor, but it depends on the Mineral content, which obviously varies across the country. Pure distilled Water (de-ionized) has virtually no conductivity. Tap water can show full mains voltage down to Earth potential, but at an extremely low current capability. Impossible to state how much, due to the variable minerals in it.
@@GSHElectrical John Ward did an experiment on this subject.: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-MF9DCNkaE8I.html Q & A: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-W1pXsMjF3Dg.html John is very good at explaining the technical stuff.
Tap water would have to be well outside of what would be an acceptable mineral content for it to become conductive to the extent that a few meters of plastic pipe would drop below 1MOhm [where technically it would pass an IR test if performed by someone with no self respect] 0.9% Sodium Chloride solution - a.k.a. the sailine drip they use at the hopsital - would be about 500kOhm/m if you put it in 15mm PEX pipe at room temperature. And really if your tap water was anywhere near this conductive something would be going horribly wrong at the waterworks and the water would be so foul that even in London they'd think it's off. That said, things like floodwater and drains can be really dangerous. Be very careful if wading through escapes of water where there may be a live electrical supply nearby.
The water in the pipe might not carry any sizeable current but it is a potential hazard when it comes to electricity. Years ago I was called out to a flat . The guy was getting a shock from a metal draining board or tap. . The fault was on a water heater in the adjacent flat and the main voltage operated trip had failed. The fault current had no where to go as the coil had burned out in the old trip . My customers flat wiring was fine it was just the fault current from the flat next door travelling through the water in the plastic pipe giving him the nasty shock . After that experience any plastic pipe installation I work on 1I still get the plumber to put in a copper section and earth that section to prevent anything like this happening again
In the 70s I used to travel round sites putting load tests on standby generators up to 750kW. We used tanks of water, raising and lowering 3 plates about 6 inches apart with 3 phase 415v on them. If the water was fresh, we only got around 30 amps so had to put salt in. Too much and it's resistance decreased as it heated up so we ended up with an inch of plate carrying 1000amps, so it was quite an art to getting it right.
So if the incoming pipework is bonded to earth and then has a plastic connection that then continues in copper, should that copper pipe also be bonded?
If you've got a metal frame under your dining table you don't need an earth lead to bond it. In general if metal objects aren't extraneous we don't need to bond them, and arguably bonding them can create a potential hazard. There are a few exceptions to this. Under Section 705 [Agricultural and Horticultural Premises], supplementary bonding is still required for all accessible metal - I believe this is because mixtures of damp manure etc makes everything essentially extraneous regardless. Historically supplementary bonding was also required in bathrooms, and there’s a lot of “sparkies” who haven’t seen a copy of the regs since 1985 and like to bond everything. But of course all bathroom circuits must now be RCD protected and so it’s unimaginable how a modern installation would require supplementary bonding in the bathroom. Even on old versions of the regs, an e.g. metal tap fed from plastic pipework installed on an acrylic bathtub does not need bonding and preferably shouldn’t be bonded.
