Closing an indoor pool in a thunderstorm

On Monday, MrsSponte took BabySponte to his swim class at the YMCA. When she got there, she was told that class was canceled due to thunderstorms, even though the Y’s pool is inside, under a thirtyish foot high ceiling.

Is there a real chance of a lightning strike causing a problem with an indoor pool, or was the Y being overcautious/believing in urban legends?*


  • Or were the lifeguards using the thunderstorm as an excuse not to work? Back in the day when I was a lifeguard (at an outdoor pool), we, on occasion, would claim that just about any loud noise was the rumble of thunder, close the pool, and take a break.

I can’t see it as being any more dangerous than any other indoor activity. I suspect they were being overcautious out of ignorance.

Is the reason in any way related to the reason why my mom calls during thunderstorms to remind me not to take a bath while there’s lightning outside?

Plumbing is one of those good grounds for lightning that hits a building.

A nearby strike could send electricity up the water pipes into the pool

No. Those pipes come from underground. I’ve never seen a pool fed by above ground metal plumbing.

Yah, I have a huge problem with the “lightning may reach the pool through the plumbing” theory. At my YMCA, for example, the (two) pools are huge; well more than a hundred people could be in them at the same time. Given the potential number of casualties, and given that we live in the lightning strike capital of the U.S.A (South Florida), where thunderstorms can brew up literally in minutes, so that an order to leave the pool may not be given in time to get everyone out, I cannot believe that the Y’s pools were not designed to eliminate as much as possible the threat.


Will all due respect the National Lightning Safety Institute has a paper titled A Cautionary Perspective for Indoor Pools.

In chapter 4 it states “six states have recommendations or regulations for suspending indoor pool activities when under lightning threat: Delaware, North Dakota, South Dakota, Maryland, Rhode Island, and Michigan. Delaware’s state code reads “during electrical storms the use of a pool (indoor or outdoor) shall be prohibited.” Several large national groups describe building interior pool hazards (*) or have recommended indoor pool activity suspension (**) when nearby thunderstorms threaten.” See

In the state the OP lives in there was a report that "There are no confirmed lightning-caused deaths of individuals in indoor pools, but there are numerous documented cases where lightning has traversed a structure and killed an individual who was inside it. They were generally using the telephone, touching metal doors or windows, or were in contact with water sources such as sinks, bathtubs, and showers. Examples of observed pool-related lightning damage include the destruction of a main circulation pump, injuries to employees touching electrical panels, the concrete footing of a slide blown apart, and even visible lightning inside the pool area. " See

So while no one has been killed people could be injured

It is probably mostly an abundance of caution thing. *See, e.g., *

And I don’t have any more details on this, but:

I defer to those smarter about electricity and the like, but I think the proposed mechanism isn’t lightning enters pool through drainpipe, but lightning strikes building, travels through wiring, enters water, leaves through drain. I have no idea if that:

  1. Could happen; or
  2. Has happened.

Whether underground or overhead, they are supposed to be bonded to earth per 250.104(A) and (B). All of the reinforcing metal in a pool shell and surround is also supposed to be bonded per 680.26.

My guess is that they are exercising extra caution, given that if a lightning strike were to occur, and if there was an unknown difference in the equipotential bonding of two adjacent places on or about the pool, and if a person were to make contact with those two unequal adjacent places at that time, injury could occur.

A long shot? You bet.

Here is the staff report I recently wrote on swimming and lightning, generally:

And the comments thread: Water and Lightning Strikes - Cecil's Columns/Staff Reports - Straight Dope Message Board

And notice that those injuries were to individuals engaged in activities where the presence of the pool was irrelevant. As I said, no more dangerous than any other indoor activity.

Lightening can hit the roof or wall of the building, and then take the pool to the grounded pipes. It’s not very likely it would hit the ground and take to the pipes to electrify the pool.