To prevent potentially dangerous electrical issues, it's imperative that you turn off the power to your pool equipment — such as pumps, motors, filters, heaters, chlorinators, and lighting fixtures. Even if you turn off the power to your pool equipment, it can still be damaged by wind, rain, and debris.
Step 1: Cover That Pool Up
Although it's not recommended for a major storm, you can use a pool cover for lighter sprinklings, or moderate rain that doesn't involve any severe wind to protect your water. Remember, the rain is acidic and is out to get your chlorine.
Remember, rain is acidic. Hence, pool overflowing from rain causes the Alkalinity and pH levels to lower. Very low pH causes pool water to turn very clear and acidic, which destroys your pool surface and equipment.
Shocking your pool isn't necessary, although, it's not a bad idea either. If you get an extremely heavy rain fall, you could shock your pool for good measure. This will help fight off any contaminants that the rain may have brought to your pool.
It is entirely safe to run your pool pump when it's raining – most of the time. Running your pool pump during rain should not affect the pumps' ability to do the job it was designed to do.
The pool will only overflow by the amount of rain in excess of the amount of rain needed to fill the pool to the top. So if your pool is the normal 3” below the top, the rain would need to exceed 3” before any additional rain would be available to overflow onto the deck.
Protect the pump motor from water damage
In addition to removing circuit breakers, consider moving the motor indoors or covering it with a waterproof material to prevent water from getting inside.
Go to the back of the filter and unscrew the drain plug. Turn the pump back on and let the water run until it reaches the point where you want to drain the water out. Turn the pump back off and put the plug back into the drain plug.
But large quantities of precipitation combined with an overflowing pool and poor drainage can cause problems such as flooding, structural damage to the surrounding buildings as well as out of balance swimming pool water chemistry. No fun.
If the pool overflows, now only will the pool chemicals be diluted, but they may contaminate the pool deck and surrounding landscape. Removing excess water quickly is important to prevent this.
Give your pool a good shock treatment 1 to 2 days before the storm hits. You can bring the chlorine level up pretty high to prolong the pool being depleted of chlorine.