Public pools have hundreds and sometimes even thousands of visitors in a day when it’s hot and sunny outside and since most of these people are there to swim to cool down and enjoy themselves, they stay in the water or longer too. You don’t have to be an expert in pool management to figure out how having so many human bodies in the same body of water is going to result in a dirty pool.
Community pools require a greater degree of pool management and care than pools at homes and even at clubs that will ask you to become a member first. The water needs to be kept sparkly clean and sterile at all times to avoid harmful diseases; typhoid and cholera are two of the main medical concerns when it comes to swimming in a public pool. In a pool that’s always crowded with so many people, there’s a very rea chance that someone peed in it and this water is going to be in contact with every bit of your skin and may even enter your mouth!
Community pool management involves the same steps that you’d take for a pool at a house but at a much larger scale; the pump needs to be running constantly, which is why not just any pumping system will do the job. Community pools require custom made pumping systems that can handle the massive swimmer load and keep the water filtered at all times. There need to be multiple filters to effectively remove all the dirt and bodily contaminants and since cleaning so many filters isn’t easy either, it makes sense to have back up filter available and ready at all times.