The shocking truth
Since we are already talking summer (thanks to last week’s blog), let’s keep it going this week. Enter, swimming pools. We love them, especially when its 90°F, sunny, and there’s not a cloud in sight. Everyone is in the pool – the kids, the dogs, the grandparents. It is a party. You might be worried about the safety of your children, your impending sunburn, the pool chemicals, or perhaps, if your BBQ chicken is burning on the grill, but have you ever thought about electricity while you swam? Probably not. Unless, you’ve ever felt a slight tingling when you touched the pool deck. If so, that’s stray voltage! If you’ve felt it, you know exactly what we are talking about. If not, it’s more common than you may think.
What is stray voltage?
A stray voltage is an electric potential (voltage) between two conductive surfaces. Ideally, there should be no difference in voltage between the two objects, but when there is, you have a stray voltage! In our case, stray voltage is coming from the grounded conductors of an electrical system nearby and the surrounding “earth” ground. When you are dealing with a pool, stray voltages usually feel like a small tingling sensation when you touch a puddle of water on the pool deck or a handrail/ladder attached to the pool. In the most extreme of cases, electricity in pools can cause paralysis and ultimately lead to drowning.
Why does it happen?
Thanks to our good friends at the Electric Power Research Institute (EPRI), we have the answers. First, uncleared electrical faults from both residential and commercial services nearby can create unsafe voltage levels on metal parts or conductive surfaces near your pool. In case you need a refresher, an electrical fault is an abnormal flow of current in an electrical system that can interrupt electricity output or cause equipment damage or failure. Electrical faults can be caused by equipment failures, human errors, and environmental conditions. Bad bonding is also often the one to blame. Missing or inadequate bonding around the pool’s exterior deck allows unwanted current to flow to the humans (or animals) in the pool during an electrical fault. There are many reasons why voltage might be leaking into your pool, but it can be as simple as a wiring mistake – carrying live current to a connection on a pool’s underwater light. Think about the constant moisture coming from the pool, too. Insulation and metals in the pool’s structure are set up for deterioration and corrosion in that kind of environment! Chlorine in the water and the alkalinity of a concrete deck can easily lead to electrical degradation or increase conductivity in the pool water.
What can you do to prevent it?
If you are a homeowner/pool owner, this is not a problem you should try to tackle yourself. Enlist the help of an electrician, electrical inspector, or highly skilled pool maintenance technician, so you can keep your family, friends, and water-loving dogs safe.
When it comes to pool inspections, there are a lot of factors to consider. Is it a public, commercial, or private pool? Chlorine or salt water? Above or in-ground? Where is the pool located? When was it built, or has it been built yet?
Since there are thousands of possibilities to consider, we are just going to stick to the basics. Be sure to check with your local or state-wide government prior to building and opening a swimming pool, as swimming pool laws regarding inspections and electricity can vary from one county (or situation) to the next.
Let’s get into the electrical testing recommendations that we would suggest, no matter the situation. Testing is usually performed on all wiring and run from the pool pump ground to lighting fixtures, drains, grating, ladders, slides, railing, and diving boards. Tests may also be performed between these individual elements to ensure that an adequate contact to ground is present for safe clearance of fault current.
Before anything else, you should be visually inspecting the wiring near the pool equipment or in the pool equipment room (if you are working with a fancy pool) to ensure that there are no violations of the current electrical code. You’ll also need to verify the electrical continuity and integrity of the pool’s bonding and grounding system with the help of a trusted insulation resistance and continuity tester. In these circumstances, a standard multimeter is not enough, as the output is not great enough to offset the presence of any voltage present in the pool. When compared to a traditional multimeter, a continuity tester can expose corroded wires with weak connections using a strong test current (usually 20 or 210 mA). For the continuity test, testing is performed on the equipment ground, not the grounding electrode system. Underwater lighting, in addition to all non-electric, metallic bonding points on all of the pool’s features will need to be tested for continuity and insulation.
There are a few more tests you should perform too. The first of which is a ground test. You should test from the service panel to the pool’s pumps, filter, heater, motors, junction boxes, switches, and piping. You may also want to check the adequacy of your grounding rod, itself. This can be done easily from any point in the electrical system with a ground tester.
Download ground testing guide
Can we just add a grounding electrode to the soil?
Unfortunately, no. Your pool is likely already surrounding by a massive grounding electrode system. Adding more grounding electrodes usually has little to no effect on improving the stray voltage issue.
So, how can we solve the problem? Let me introduce you to the equipotential bonding grid. If all of your pool’s conductive elements are bonded together in a common equipotential bonding system, then you are set. Unfortunately, if there are errors in this system and your pool is already built, this can be tricky. In these circumstances, the nature of the repairs may be costly, difficult and time-consuming. Luckily, the tests we discussed above can help identify specific issues in your pool’s mechanical and electrical system.
As Benjamin Franklin said, “An ounce of prevention is worth a pound of cure.” In this case, he is more than right. If you’re thinking of building a pool, prevent stray voltage altogether by installing an adequate and electrically sound equipotential bonding grid. If you are in the latter group (and your pool is already built), enlist the help of an electrician and ensure you are running the continuity, insulation, and grounding tests that we recommended above.