# Lightning and indoor pools **URL:** \ **Category:** Factual Questions\ **Created:** [August 18, 2002, 8:44pm UTC](https://boards.straightdope.com/t/lightning-and-indoor-pools/124505 "2002-08-18T20:44:55Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Acco40](https://avatars.discourse-cdn.com/v4/letter/a/58956e/32.png) [@Acco40](https://boards.straightdope.com/u/Acco40)\ **Post date:** [August 18, 2002, 8:44pm UTC](https://boards.straightdope.com/t/lightning-and-indoor-pools/124505/1 "2002-08-18T20:44:55Z")
Can I be electricuted by lightning while swimming in an indoor pool? Today I was told to get out of the water when doing lap swimming at the health club because they said I could be struck. I know that water is an excellent conductor, but would lightning really be a concern if I was swimming indoors? I’ve never heard of a policy like this at any other club I’ve ever been a member of — is this a common health club policy? ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [August 19, 2002, 12:24am UTC](https://boards.straightdope.com/t/lightning-and-indoor-pools/124505/2 "2002-08-19T00:24:07Z")
Not only is it common, but it is probably universal, to prevent the remote possibility of electrocution. Swimming pools are grounded, so the possibility is not great, but it is emptied in any event at the first sound of thunder or sight of lightning. ---
**Author:** ![d12](https://avatars.discourse-cdn.com/v4/letter/d/71c47a/32.png) [@d12](https://boards.straightdope.com/u/d12)\ **Post date:** [August 19, 2002, 1:08am UTC](https://boards.straightdope.com/t/lightning-and-indoor-pools/124505/3 "2002-08-19T01:08:46Z")
Electricity will ALWAYS take the path of least resistance. If it’s happened once it’ll most likely follow the same path unless something has influenced it to do otherwise. ---
**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\ **Post date:** [August 19, 2002, 3:47am UTC](https://boards.straightdope.com/t/lightning-and-indoor-pools/124505/4 "2002-08-19T03:47:18Z")
Found this. [http://www.lightningstorm.com/ls2/faq/index.jsp](http://www.lightningstorm.com/ls2/faq/index.jsp) > [@](#): > > Question: Is it necessary to evacuate a pool during lightning? > > Yes. There are a few cases in and around swimming pools every year in the U.S. During the summer of 2000, two boys were killed at an outdoor pool in Florida. Documented cases of indoor pool lightning victims are scarce. The whole indoor or outdoor pool complex should be considered unsafe during lightning unless proven otherwise. The open surface of the pool is one factor, but the power, plumbing, and mechanical connections to the pool are a very important factor, too. Water and electric lines are very good conductors. The most likely scenario is for lightning to hit a utility pole outside a pool. The current then travels through wires into the pool area. Every pool has a pump, and the pump is designed to move water. That connection can be the site of a transfer of lightning current from the power system into water in the pool, then to wading pools, the shower area, and anywhere there is standing water. Everyone in contact with water in the complex could be a lightning strike victim. Lightning safety experts recommend staying out of the water for 30 minutes after the last flash or thunder. Studies found that waiting 30 minutes eliminates most lightning risks as the storm leaves the area. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [August 19, 2002, 5:00am UTC](https://boards.straightdope.com/t/lightning-and-indoor-pools/124505/5 "2002-08-19T05:00:19Z")
There are a couple of misconceptions in the above posts. > [@](#): > > \*Originally posted by d12 \* > \*\*Electricity will ALWAYS take the path of least resistance. If it’s happened once it’ll most likely follow the same path unless something has influenced it to do otherwise. \*\* Two things here. First, electricity does follow the path of least resistance, but it’s not quite like some people seem to think. Consider the simplest case, that there are 2 different paths for the electricity to take. This is what we engineer types call a “current divider” because the current divides between the two paths (duh, ok, engineers aren’t very creative with names, what’s your point…). The thing is, not all of the electricity takes the path of least resistance. The current will divide itself proportionally according to the resistance. The path that has the least resistance will get more current, but the path with the most resistance still gets some. The second thing from the above quote is that lightning isn’t quite that predictable. Lightning forms “streamers” that reach up from the ground and down from the sky. Whichever one happens to make contact first is where the bolt goes through. It may go through the branch of a tree one time, pick another branch the next time, or maybe pick a nearby post. Who knows. > [@](#): > > \*Originally posted by Acco40 \* > **I know that water is an excellent conductor** Actually, as far as conductors go, water is a pretty poor conductor. The thing that makes water so dangerous is that while it is a poor conductor, it is in fact a conductor (compared to something like wood, which is a fairly good insulator), and also that it takes a very small amount of electricity to do the body quite a bit of harm. Electricity kills you primarily from one of two things, either it cooks you to death or it interrupts your heartbeat. Anyone who manages to survive a lightning strike will likely spend months in the hospital just recovering from the burns. It takes quite a bit of energy to cook you to death. It takes a very small amount of energy to interrupt your heartbeat however, and once it is out of whack it very often won’t recover on its own, so unless someone is standing next to you with a portable defibrulator, you’re toast. The minimum amount of electricity thought to be able to kill you (for ethical reason’s we’re obviously not really sure of this) is about 5 milli-amps (0.005 amps). To put it in perspective, your circuit breaker on your outlet (where you plug in your hair dryer) probably trips at 15 amps. So, even though water is a really poor conductor, it takes only a tiny fraction of the current that the line is capable of supplying to stop your heart. That’s why you need to keep the hair dryer OUT of the tub, thank you. Now let’s put this in perspective with a lightning bolt. Your hair dryer is plugged into a 120 volt outlet (maybe 220 depending on where you are in the world). A lightning bolt by comparison is millions of volts. I’m not sure of the exact ampere rating of a lightning bolt, but “pretty freakin high” is probably accurate enough for this discussion. When the lightning bolt hits the tree outside, the club building, whatever, there are going to be multiple paths that it will take. If it gets into the building steel, that’s a really good conductor, so it will likely follow that for the most part. But, remember what we have here are a bunch of current dividers, so some of the current is going to go through the not so good conductors, i.e. the swimming pool water and the people in the pool. Granted, only a tiny fraction of the lightning bolt’s energy will go through anyone in the pool, but keep in mind that a tiny fraction of a lightning bolt is more than enough to get your heart out of whack. I would think that it would be a pretty rare event, but definately not impossible for you to be electricuted in an indoor pool. ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [August 19, 2002, 5:01pm UTC](https://boards.straightdope.com/t/lightning-and-indoor-pools/124505/6 "2002-08-19T17:01:41Z")
> [@](#): > > \*Originally posted by engineer\_comp\_geek \* > \*\*Actually, as far as conductors go, water is a pretty poor conductor. \*\* Yes, pure water is a poor conductor, but people sweat in a pool and exude plenty of sodium ions. That, together with other impurities, makes it a good conductor. And BTW, the spelling is “electr_o_cuted.” And by definition if one is electrocuted, he or she is DEAD. I see newspaper reports that so-and-so was electrocuted and spent a week in a hospital. If one is electrocuted, that person will spend a long time underground. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 19, 2002, 10:53pm UTC](https://boards.straightdope.com/t/lightning-and-indoor-pools/124505/7 "2002-08-19T22:53:30Z")
Truly pure water is a half-decent insulator. Tap water or pool water or lake water is a conductor, but it’s still a pretty poor conductor compared to most metals. The three problems are that first, there’s generally an awful lot of water in a pool, so a current path can be very wide (this decreases the resistance), second, a person in a pool has most or all of their skin in contact with the water, and third, as **engineer\_comp\_geek** points out, with lightning, a poor conductor is all it takes. As for electrocution, a person is electrocuted if their heart stops from the shock. By some definitions, “heart stopped” = “dead”, but it’s still possible (in some cases) to revive someone whose heart is stopped. Of course, even after the heart is re-started, there might be very good reasons for keeping the victim hospitalized for a while. ---
**Author:** ![Malice](https://avatars.discourse-cdn.com/v4/letter/m/278dde/32.png) [@Malice](https://boards.straightdope.com/u/Malice)\ **Post date:** [August 19, 2002, 11:27pm UTC](https://boards.straightdope.com/t/lightning-and-indoor-pools/124505/8 "2002-08-19T23:27:12Z")
> [@](#): > > \*Originally posted by engineer\_comp\_geek \* > \*\*Now let’s put this in perspective with a lightning bolt. Your hair dryer is plugged into a 120 volt outlet (maybe 220 depending on where you are in the world). A lightning bolt by comparison is millions of volts. I’m not sure of the exact ampere rating of a lightning bolt, but “pretty freakin high” is probably accurate enough for this discussion. \*\* Average peak current in a cloud-to-ground lightning stroke: 100,000 Amperes, according to this site: [http://wvlightning.com/facts.htm](http://wvlightning.com/facts.htm) 100,000 amps… Yup, that’s pretty freakin high all right. ---
**Author:** ![barbitu8](https://avatars.discourse-cdn.com/v4/letter/b/839c29/32.png) [@barbitu8](https://boards.straightdope.com/u/barbitu8)\ **Post date:** [August 20, 2002, 2:31am UTC](https://boards.straightdope.com/t/lightning-and-indoor-pools/124505/9 "2002-08-20T02:31:14Z")
[Dictionary.com](http://Dictionary.com): > [@](#): > > e·lec·tro·cute Pronunciation Key (-lktr-kyt) > tr.v. e·lec·tro·cut·ed, e·lec·tro·cut·ing, e·lec·tro·cutes > To kill with electricity: a worker who was electrocuted by a high-tension wire. > To execute (a condemned prisoner) by means of electricity. A person is electrocuted only if he is killed. Show me one dictionary that gives the definition \*\* Chronos \*\* gives.