Which chemical is added to water in swimming pools to keep water clean?

chlorine that's what you can smell at Swimming Pools too

New ans: If you can smell chlorine at an outdoor pool means that the pool does not have enough chlorine in it to sanitize the water. More needs to be added to meet minimum standards set by local and regional codes. It also means that the people responsible for maintenance are not doing their jobs correctly. It also means that you could be more suseptable to a desease or infection of some sort.

- chlorine and bromine for desinfection (characteristic smell)

- algaecide - kills algae

- water balance chemicals - to adjust acidity and alkalinity and remove water minerals