Rainfall dilutes pool chemistry levels and lowers the readings for pH, alkalinity, hardness, stabilizer, and chlorine.
While light rain will have little, if any, effect on pool water, heavy rainfall can dilute a swimming pool's chlorine levels, allowing bacteria and algae to start growing. Rain can also lower a pool's pH. Chlorine becomes hyperactive at a low pH, causing it to be used up more quickly than normal.
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.
Heavy rains will deplete many of the chemistry levels in your pool. Generally your alkalinity will drop significantly. It is a good idea to have Alkalinity, Muriatic Acid, Chlorine (or Salt), and Shock on hand to be able to test your water and treat your pool immediately after the rain stops.
When rainwater and 'run off' enter the pool, they can change your water's pH, calcium hardness, total dissolved solids (TDS), alkalinity, and other chemical levels as well as bring contaminants such as dirt and debris into the pool.
When preparing your pool for a storm, leave it uncovered. Installing any kind of cover across the pool will not do much to protect against dust and contaminants because storms often bring strong winds and heavy rain that can cause the cover to lift off your pool.
"Heavy rain dilutes pool chemicals, especially salt and chlorine, which causes the pool to turn green. This means the water is not sanitised or healthy, so it's vital to address this.
Skim the pool to remove excess debris. Shock the pool and run the filtration system for at least 12 hours. Test and re-balance pool water.
Since rain is diluting your pool, you may expect that it will reduce the acidity of your pool water. However, all rain in the US is acidic due to pollution, so rain actually decreases your pool's pH – in other words, the pool water becomes more acidic.
Answer: It should not matter much. It could help to filter debris and contaminants the rain washes into the pool. However, lightning can be a concern with the filter running.
Normal, clean rain has a pH value of between 5.0 and 5.5, which is slightly acidic. However, when rain combines with sulfur dioxide or nitrogen oxides—produced from power plants and automobiles—the rain becomes much more acidic. Typical acid rain has a pH value of 4.0.
Rain delivers algae spores and debris to pool water and it is these things that cause problems. Algae spores are usually present in the air. Riding the air currents hither and yon in order to sometimes land in hospitable locations is part of algae's reproductive strategy.
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 water level is too high the debris floating next to the opening may pass by without being pulled into the skimmer. However if the water level is too low it may cause the skimmer to suck air into the system. If this happens you may run the risk of burning up your pool pumps motor.
Should the green be due to pollen, there may be little to do in the way of minimizing the discoloration short of erecting a building around the pool. Fortunately, assuming there are no allergies to the pollen, it is safe to swim in a pool with that as the cause for green water.
A pool turns green when there is algae in the water. There are several reasons why algae could grow, but it is most commonly caused by prolonged exposure to the sun, rain and temperature spikes. These factors affect the chemical balance of the pool and result in the pool turning cloudy and/or green.
When rainwater and 'run off' enter the pool, they can change your water's pH, calcium hardness, total dissolved solids (TDS), alkalinity and other chemical levels as well as bring contaminants (e.g. debris, dirt) into the pool.
Swimming pool owners can add disinfecting and stabilizing chemicals as they please when it rains. However, continuous rain will adversely affect the water's chemical balances. This is because rain picks up atmospheric contaminants, such as organic materials and even algae spores, when it falls.
High chlorine levels decrease the pH of your pool's water, making it more acidic. The more acidic the water, the higher the likelihood of corrosion. This corrosion can affect metal piping, equipment, and the surface of your pool (tiles, liners, concrete, etc.).
If your pool pump manufacturer has declared your pump is rain safe, you can leave it on in rainfall. Nevertheless, during a thunderstorm, it is highly recommended that you switch off and unplug your pool pump to prevent any costly and irreversible damages to your pool equipment.
We recommend that our customers run their pumps rain or shine UNLESS we have an electrical storm. In that case, lightning could strike an outside circuit, which could damage your pump and other equipment. If you're worried about lightening, turn the pump off or shut off the breaker.
One of the causes of a high chlorine demand is an excessive buildup of algae and phosphates. Although you're adding chlorine to your water, bacteria or algae are overpowering the chemicals causing it not to show up on tests strips or in water kits.