OK, so I know this has been discussed at many of the past conferences, but I have a question.  How many of you close your indoor facilities during a thunder & lightning storm?  And if you do close, WHY?

I am trying to gather as much info as I can to present to my staff.

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Bob -

Our indoor pool is in Roseville, CA and we don't deal with too much thunder & lightning storms and have only been open about year, so we are kind of new to this topic. But we have currently taken the stance that is the same as our outdoor pools and we would clear the pool as deemed by our outdoor pool policy. I will be interested to see others comments.


but why do you have that stance?

We clear the pool as well, simply because it seems to be the industry standard, and is recommended by the national lightning safety institute. (See the 1st link - in the 2nd link below it mentions that several states have actually included it in their code.)  Tom Griffith's great article in AI a while back stated that he couldn't find any instances of injury or death from lightning strikes and indoor pool swimmers, but the section of the NEC he mentioned didn't really support what he was saying, and too many other organizations advocate otherwise.  (see the "letters to the editor section on the AI magazine page)



If more information came along with substantiated data saying otherwise, I could see changing policies, bat at this time I don't have enough information to stray from what is practiced by almost everyone else in the industry.

I've seen a few different guidelines. 1)Use same guidelines for indoor used for outdoors; 2)Indoor pool is fine if properly grounded and bounded; 3)evacuate pool and shower areas if cloud to ground lightning is within 6-8 miles.


Personally, I evaculate if cloud to ground lightning is within 6-8miles as recommended by the National Lightning Safety Institute.


There is evidence to support the facility is safer if it is properly grounded and bounded but there are very few that truly fall into this category. If you have portable guard stands, metal bleachers, other metalic objects that are in proximity of the pool and not grounded to the building there is a risk.


To my knowledge there have not been any documented injuries/deaths by lightning striking an indoor pool (someone correct me if I'm wrong), but there have been cases of lightning striking objects in and around indoor pools.


So what I'm hearing is that it is the "standard of care" but no one can tell me why.  If the arguement is made that there is a "chance" that it might happen, then we shouldn't let anyone swim because they may drown, have a heart attack, seizure, etc.  If we want to eliminate all "possibles" we wouldn't allow swimming.  The NLSI says that it "could" pass through the electrical system or the plumbing.  So the electrical current would have to pass through the curcuit breaker, and if those didn't trip then it would all go into the pool?  Or if it comes in with the plumbing (which in most cases is PVC which doesn't conduct) it would have to pass through the pump, the filter (UV system if you have it) the heater, and then to the pool.  I think there is a better chance of being hit by a car in the parking lot of the pool than of being struck by lightning in the pool.
I completely agree with your last statement. There is a beter chance of being hit by a car.

I agree in that you do run a higher risk of being hit in a parking lot!


I don't think it's an "all or nothing" answer though, otherwise we'd all be out of a job!  We all know we can't eliminate risk entirely, but we take steps to eliminate it by following established guidelines by experts in the field. (especially ones that can defend us in court when needed :).  If I were to build a parking lot, I'd follow the standards set forth for safety by architectural/engineering organizations.  When I buy a car, I want one that has high safety ratings and will keep me safe.  And when I establish protocols in response to electrical storms, I follow the recommendations of experts in the field, such as NLSI.


Which isn't to say 'the experts' aren't ever wrong of course...  I guess what I'm saying is I don't have enough information otherwise to feel comfortable sticking out my neck so far by establishing alternative policies.

Bob, I think you're spot on with your statements regarding the dangers of driving and swimming. And you are definitely correct in believing that a patron would be far more likely to be injured engaging in either activity.

What I think you may be missing, though, is that we have systems in place to manage the risks associated with swimming (ie. lifeguards, swim testing, PFDs, etc.) and driving (ie. speed limits, seat belts, licensing requirements, etc.).

As is the case with all weather-related phenomena, we just don't have the technology or resources to predict or manage the dangers as well as we do with other dangerous activities. So, rather than simply ignoring the "chance that it might happen", we do our very best to protect swimmers. When it comes to lightning near water - regardless of indoor pools, outdoor pools, or brown water - our only defense is clearing the pool. If we had other alternatives than maybe clearing the pool wouldn't be necessary.

I think the issue is that someone cried "wolf."  How can you not close your indoor pool when there is an opinion otherwise.  In the extremely unlikely event that something happened, you would be trashed in court.


Even the NLSI admits that there is no evidence anyone has ever been hit or hurt in an indoor pool.  They editorialize that it is because it is not reported.  I find that hard to believe with something as sensational as a lightning strike, especially if there were injuries.  It is very easy to say it has happened once (although they can't); it is impossible to say it will never happen (that can't be conclusively determined scientifically).  There has been one incident in Quebec where the lightning reportedly came in through a window and struck the pool.  As far as I know, the 20 people in the pool suffered no ill effects.  Interesting.


I worked several years at indoor pools in an area prone to thunderstorms.  We never had any problems even when the building was hit directly, which because of the height of the structures happened with regularity.  It did cause problems, as the hit would shut down the pumps and we would have to spend time recoating our DE filters.  My opinion, based on my experience, is not in agreement with the NLSI.  However, I am trapped by the problem that something cannot be scientifically proven to never happen or can't happen.  Doesn't the lack of any injury statistics mean anything?  Of course don't let the insurance company that made you remove your diving board influence you.


I am a very firm believer in closing an outdoor pool at the first sign of lightning or thunder.  I was about 50 feet from a pool that I watched get hit by lightning.  It destroyed the pump and filter.  Unfortunately, I have seen many outdoor pool operators reluctant to close their pool even when lightning is present all around them.  I have even had them refuse to do anythng when I was actually at the pool telling them "officially" to close their pool.  I think much more education and work needs to occur at outdoor pools before we worry so much about the indoor pools.

Check you local codes as some do require adherence to the NSLI recommendations to close when the Flash to Bang ratio indicates a storm within 6-8 miles even for indoor pools. If you have an indoor facility and you don't close when there is a storm in the vicinity at least have an EAP for power outages and know that if your filter stops you have to get people out and cannot put them back in until the filter is back up and running and again check your local codes for how long it has to be running prior to occupancy.

When we were developing our aquatics best practices guide we discussed this topic at length. At the time, we were also struggling to find any evidence of there ever being a recorded injury or fatality.

Our stance on lightning policies forever changed though after one of our loss prevention representatives heard a first-hand story from one of our YMCA customers. The Y employee, who also happened to be the Aquatics Director, received a report from a water aerobics instructor that reported feeling a minor shock in the pool during a thunderstorm. It turns out that several of the water aerobics participants also felt the shock. Luckily, no one sustained an injury. But the swimmers first-hand accounts were enough for us to formally recommend all of our customers to clear the water during a thunderstorm.

If anyone would like to speak directly with the loss prevention representative that spoke with the aquatics director, shoot me a message and I will do my best to put you in contact.

John - that is very interesting.  What did you conclude as a recommendation for best practices to define what "during a thunderstorm" means as far as specific proximity?  Are you endorsing the NSLI recommendation?


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