Electrical shock from my pool water!

[plucky71]

Have you ever heard of such a thing? I am actually getting shocked from my pool water.
I reached my hand into the skimmer basket and received a electrical shock. I am able to duplicate it all around the entire pool. I only feel the shock if I have some type of cut on my hand and the shock pinpoints right at the wound. It only works if my feet are wet or the concrete is wet. It wont do it if I am standing on the fiberglass 6" rim going all the way around my pool.
When it happened to me, my son said, now you will believe me. Apparently He told me about it last year and I blew him off.

Any suggestions?

 

[CraigMW]

Sounds like a bonding issue. Do you know if the pool shell and the deck are tied together by a bonding wire? This is not the same thing as an equipment ground. I'm not sure if bonding is typically required in fiberglass pools, but it could be that something metal in the pool (e.g. pool ladder, light niche ring, etc) is at a different electrical potential than the deck itself. If this is the case, the only fix is to have the water bonded to the rebar in the concrete deck, and then to the equipment at the pool pad. Unfortunately, this is tricky to figure out.

 

[danpik]

Definitely a bonding issue. This "shock" you are feeling is basically the same as a static shock. Do you have a water bond? Do you have a bonding system?

I wrote this a while back to help some people with understanding the difference between bonding and grounding......

Bonding and grounding are two often misunderstood concepts.

To start, we will look at grounding first. In the 120 volt electrical supply system for your pool pump there are 3 wires. Hot, Neutral, and ground. The hot and Neutral serve to move power from the source and back to the source so the pump can run. The ground wire in this system serves only as a non resistive conductive path back to source should something happen internally in the pump. For example, if, for some reason, the hot wire came in contact with the motor housing, the housing could become energized. Without the ground present, the housing could sit there waiting to shock any unsuspecting person or animal who happened to touch it. You would be the conductor to ground. Ground being the ground you are standing on. Now, because the resistive properties of the ground you are standing on are too high for the current to short circuit back to the source, it would most likely not trip the overcurrent protection (fuse, breaker). A couple of times here I have referred to "source". This is the power company transformer on the pole out at the street. The hot and neutral connections are both on this transformer and the returning current wants to get back to what is called the center tap on the transformer either via the grounding system or the neutral system. If there is a ground wire present in the circuit, the hot wire coming in contact with the motor housing would immediately trip the overcurrent protection as there would be a dead short in the system.

Bonding. The really mis-understood concept.
Have you ever experienced a static shock?...You know, you shuffle your feet across a carpet in the dry season and touch a metal doorknob. If you were bonded to that doorknob when you shuffled across the floor you would not have felt it when you touched it. Everything in the universe has what is referred to as electrical potential. Humans have a certain potential, a piece of steel has its own potential, water its own, etc, etc, etc. Most times this potential is not different enough to feel it. When you shuffle your feet on the carpet though, your potential changes from that of the doorknob. When you get close enough to the doorknob though both you and the doorknob want to get to the same potential. when that happens, a spark jumps the gap and evens out the potential. Fortunately there is little amperage behind it so there is no chance of getting electrocuted. Now, lets look at your pool. your pool pump is grounded back to the source thru the ground wire. But, it still is at some level of potential. Your pool water is at some other level of potential, your heater at its own level, heck, the ground you are standing on is at some level of potential. This means that all of the items in the vicinity have some varying degree of electrical potential. Under most circumstances these potentials are so close to each other that you never feel any kind of shock. however, every once in a while something happens to change the potential of one of the items. It could be a stray voltage induced from an underground electrical service, It could be a slight resistive leakage of current in your pumping system. What ever it is there is a potential difference. Now imagine you are getting out of the pool and as you touch the metal side of the pool you get the shock of your life. Hopefully not enough to kill you but a good shot none-the-less. Guess what? You just became the bonding conductor in the system. Had all of the components in the system been bonded together by the #8 bonding wire you never would have felt it. The wire is a non-resistive path between all of the components and since electricity is lazy, it will take the least resistive path. This bonding system will also protect you if you were standing on the ground and decided to touch the water to see how warm it is. If the bond is in place there would be no potential difference between the water and the ground even if there were a stray current floating around.

Hopefully this helps clear some of this up

 

[jasonknox]

danpik - That was a great explanation. I love the static electricity example, anyone can relate to that.

 

[plucky71]

Thanks for the replies. I do not know if it is bonded. I am assuming that it does not since we are getting shocked. Since we can only feel it through a cut in our skin it must be a very low amount. How much of a safety hazard is this?

 

[ShockerLU3]

I would classify the danger as pretty extreme. Look on the back of your pump motor. There should be a bare or green covered large guage wire connected to a screw or lug there. Make sure it is not loose or corroded. If it is, a little sandpaper or wire brush and a screwdriver or wrench is all that's needed to correct. The connection should be bright copper on the wire and shiny metal on any lugs/ terminals. Tight means tight with a tool, be it a screwdriver or wrench. After you check there, follow the wire to it's other end to check for the same issues there. It should be attached to something metal and may travel in a ring around the pool underground.

 

[CraigMW]

The voltage differential is probably only a few volts, but the danger is that the pool is not bonded. This means that if any significant voltage does enter the pool, a person stepping into the pool would serve as the grounding path and experience that voltage, which could be hazardous. You might want to have it looked at by a professional. At a minimum, call your power company and ask them to test the differential. It sounds as though there may be some power equipment that is causing a ground voltage imbalance.

 

[Ohm_Boy]

The comparison to a static shock may be misleading. A static shock occurs when a charge builds up and discharges through someone, but once the discharge happens, the charge is dissipated, and it's done. This is not the case with a current in an unbonded pool, as the voltage potential will not 'go away' once a discharge has occurred. The voltage potential in this case will be sustained even after contact is made.

Additionally, the voltage is generally not a good indicator of the level of danger in a stray current situation. The voltage may be only a volt or few volts, but there may be literally tens or hundreds of ampacity in the feed. Realize that in some cases, this *could* be emanating from the power distribution grid itself, which for all practical purposes has an unlimited current potential.

Dry, undamaged human skin can have a surface resistance of 20,000 to 100,000 ohms, which will limit the current that can flow through one's body at low voltages, but once the outer layer is breached, resistance to current flow drops to around 300 ohms or less. Immersion in water will also lower the outer skin resistance. At these low levels of resistance, current can flow easily with only minimal voltage potential.

According to NIOSH*, 16 milliamps (0.016 amp) is as high a current as an average man can grasp and still let go. A little bit of Ohm's law calculation tell us that this can be achieved through the human body with only 5 volts. A 20 milliamp current through the body can be fatal.

This is what the bonding mechanism is designed to protect against. Whatever current would be presented due to voltage potential would be conducted through the virtually zero ohms of resistance of the bonding conductors, and not through the 300 ohms or so of a human body.


* - NIOSH publication 98-131, worker deaths by electrocution http://www.cdc.gov/niosh/docs/98-131/pdfs/98-131.pdf

 

[danpik]

The comparison to a static shock may be misleading. A static shock occurs when a charge builds up and discharges through someone, but once the discharge happens, the charge is dissipated, and it's done.

Agreed, It was not intended that there is a direct comparison between a static shock and stray voltage floating around a pool. It was intended to serve as an example of howbonding works. It may need some tweeking to the wording. The reality isthough, for the sake of the original posters question, that there is a bonding issue with the pool. From the specs the OP gave the pool is an inground fiberglass build. Acording to the NEC a non conductive surface does not need to be bonded. However, there should be a bond loop in the concrete deck, if there is a concrete deck and tied to all metal components in the pumping/filter/heater system. The last few NEC updates also call for a water bond of 9 square inches minimum. This has to be a conductive, non corrosive material in contact with the water. Should there be a stray voltage source energizing the water you should never feel it.

Two things need to be done by the OP. the bond needs to be checked and verified and the source of the stray voltage needs to be identified and fixed. One will be easier than the other. The bond can be checked visually and with an ohm meter. The stray voltage can be something as simple as a defective extension cord laying on the ground. I recently had one that the power company wound up digging up the street to fix a defective neutral feed.

 

[Ohm_Boy]

Sorry, I did not mean to imply that your post was somehow bad, wrong, or remiss. I just wanted to clarify the static-vs-continuous thing, Then, as usual, having started typing, I couldn't stop spouting until a few paragraphs had passed.

 

[plucky71]

I would classify the danger as pretty extreme. Look on the back of your pump motor. There should be a bare or green covered large guage wire connected to a screw or lug there. Make sure it is not loose or corroded. If it is, a little sandpaper or wire brush and a screwdriver or wrench is all that's needed to correct. The connection should be bright copper on the wire and shiny metal on any lugs/ terminals. Tight means tight with a tool, be it a screwdriver or wrench. After you check there, follow the wire to it's other end to check for the same issues there. It should be attached to something metal and may travel in a ring around the pool underground.

The connection lug on the motor was bad. I replaced it and it made things better. I can no longer feel a shock, but my son can still feel it. He said it is not as bad as it was. I will work on it some more tomorrow.
Even if the shock is gone, I would assume I still need to have the electric company look for the source.

 

[plucky71]

Also, the heater is not connected to the bonding wire. Is there a special location to connect to? I will also do that tomorrow.

 

[danpik]

There may be a lug somewhere on it to connect to. I use a pipe clamp on the heat exchanger to fulfill the water bond requirement when heaters are hooked to pool.

 

[plucky71]

Another question. The wire comes out of the ground and then to the equipment. Then it does not attach to anything else. Should it end at a grounding rod or something?

 

[CraigMW]

There may be a lug somewhere on it to connect to. I use a pipe clamp on the heat exchanger to fulfill the water bond requirement when heaters are hooked to pool.

Danpik: Thinking out loud here, so don't take offense. Isn't the water bond supposed to be in the pool, for example, in the light niche? If it takes place at the heater, that's a pretty long pathlength back to the pool. Given the resistance of water, it probably wouldn't serve much use for bonding. In addition, the water bond would be intermittent since any break in the flow (e.g. gate or 3-way valves, or pump turned off) would prevent current flow. I will admit that it's an interesting idea, and maybe this is done routinely. I'm just trying to wrap my head around the logic.

 

[plucky71]

I think he was just answering my question of where to attach the bonding wire at the heater.

 

[Ohm_Boy]

The wire that bonds the outer case of the motor is [should be] connected to a bonding loop underground. It should make a continuous loop around the pool, and should connect to the re-bar in the concrete. It should connect to any metal [conductive] parts of the pool itself.

All metal or conductive parts of your pool system, as well as the water itself, should be connected together. This has nothing to do with any grounding system or rods. It is strictly to keep all touchable components at the same voltage potential (whatever that may be) so that you cannot be shocked by being between any of them.

 

[plucky71]

Thanks. I am still working on it.

 

[plucky71]

I connected the bonding wire to the heater and the pump. It still shocked my amazing handsome kind enthusiastic loving cool son . :idea: I removed the metal ladder from the pool, and presto! No shocko!

 

[danpik]

There may be a lug somewhere on it to connect to. I use a pipe clamp on the heat exchanger to fulfill the water bond requirement when heaters are hooked to pool.

Danpik: Thinking out loud here, so don't take offense. Isn't the water bond supposed to be in the pool, for example, in the light niche? If it takes place at the heater, that's a pretty long pathlength back to the pool. Given the resistance of water, it probably wouldn't serve much use for bonding. In addition, the water bond would be intermittent since any break in the flow (e.g. gate or 3-way valves, or pump turned off) would prevent current flow. I will admit that it's an interesting idea, and maybe this is done routinely. I'm just trying to wrap my head around the logic.

None taken. The NEC does not spell out where the water bond has to be, It only spells out that it has to be a water contact area of at least 9 square inches. I will agree that some systems that have bypass loops in place for heaters could circumvent the bond and that would have to be taken into consideration when designing the bond system.There are a few devices out on the market that are designed to be a water bond. One good one is mounted in the skimmer and sits tight against the wall. Another one replaces a hose connection at the pump or skimmer with a stainless steel fitting that can be bonded to. Resistance of the water is not realy an issue in this situation as the bond is meant to equalize potential difference by eliminating resistance between two different potentials. Without the bond in place you become the resistive path between the potentials and it can sometimes be painfull. Here is an incredible video of how voltage potential works. http://www.youtube.com/watch?v=LIjC7DjoVe8 At 1:38 in the video he somewhat explains how potential works.

Remember, in a grounding system, we are flowing current from the defect in the electrical system back to source. The ground wire acts as a low resistance path so you don't get shocked. In a bonding system we are simply keeping two or more voltage potentials equal. As long as the bond between these different potentials is of low enough resistance they will equal out and you don't become the conductor