The proper balance is quickly restored. After large storms, which add 2-3 inches of rain water to your pool, you'll have to add chemicals as needed and wait to make sure they don't adjust too high. Restoring your pool's proper balance will require more than just adding chemicals.
The Department of Environmental Health recommends avoiding activities such as swimming, surfing, and diving for 72 hours after it rains. Research has shown that the risk of infection is the highest during and the day after rain, and declines to around normal levels after three days.
Shock the pool
It's not time to fix your pool chemistry just yet – that said, there's nothing wrong with giving your water a little boost. After heavy rainfall, your pool's chlorine levels will be much lower from fighting off contaminants. Shocking your pool replenishes the chlorine lost from the rain.
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.
Use shock treatment on your pool one or two days before the storm. Add chlorine levels significantly during the treatment and let it run for 24 hours to allow the treatment to fill the entire pool. Make sure all furniture or items around your pool are safe to prevent injury to persons or property.
The main time to deal with the mess is after the storm has passed. However, it's not a bad idea to pretreat your pool water. Adding some algicide to your pool water will help you get out ahead of the algae. It can help prevent an algae bloom when the rain clears and the sun comes out and warms the water.
The quick answer is no. You don't need to drain your pool, as there is no risk to your pool by it being full. The only thing you lose with a pool filled to the rim is your skimmer's surface cleaning action. Overall, it still draws water and the equipment is just fine.
Pool overflow usually happens during a storm or flood and is more common in areas with heavy rainfall or where the amount of rainfall is more than 3 inches. Usually, pools are built to handle up to 3 inches of rainfall. But if the rainfall exceeds 3 inches, many pools will experience pool overflow.
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.
The best measure to keep your pool from overflowing and causing damage is to make sure that your yard drains properly; try running a hose to see where the water runs to and how fast. Make sure the deck is pitched slightly away from the pool to keep contaminants flowing out of your pool rather than into it.
While shocking and adding algaecide is effective in getting rid of algae, it should not be done together. This is because when you mix chlorine and algaecide together, it renders both of them useless. Hence, you should first shock the pool and wait for the chlorine levels to fall below 5 PPM.
The presence of too much algaecide can lead to a foamy pool water. Small bubbles will begin to be produced as the water is pushed through the return jet and back into the pool. Do not confuse these bubbles and foam with another common problem, which is air in your pool lines.
Chlorine—yep, your typical sanitizer—is much more effective at killing algae than algaecide is. Even if your water gets cloudy and your walls get slimy, chlorine can still kill it. That's because chlorine oxidizes bacteria and single-celled algae, which means they trade electrons.