Chlorinating

 

The most popular chlorinating compounds are hypochlorites, like sodium hypochlorite and lithium hypochlorite: https://en.wikipedia.org/wiki/Hypochlorite. These break up easily in water, releasing pure chlorine, and the other elements don’t do much in the water.

The alternative solution for chlorinating and disinfecting is saltwater pools. These use a small elecrolyser that splits the salt into sodium and chlorine.

This allows owners to fill up the reservoir of salt just once or twice a season, and then the salt will slowly be turned into just enough chlorine to keep the water disinfected.

Normal pool care requires chlorine refills every few days, and more powerful chlorine “shocks” every two weeks or so, so saltwater pools have a clear advantage, but they’re more expensive to install and replace.

Closing Pool Chemicals

The chemicals used to close a pool are slightly different from the ordinary ones. You can find a few examples at Watson’s closing pool chemicals. Some of these are similar to normal chemicals, and some are different.

For example, if you’re closing your pool for the winter, you need a strong shock treatment and a strong algaecide. These need to be powerful enough to protect the water you leave from developing bacteria or algae throughout the entire winter.

Water Hardness

Hardness is measured in parts per million, or ppm. It’s measured in calcium—that’s not the only mineral that can make water hard, but hardness is measured by how much calcium would be required to make the water as hard as it is with all of the different minerals in it.

Average hardness is 75 to 150 ppm. Above that is considered to be fairly hard. The recommended hardness for swimming pools is 200 to 400 ppm, which is quite hard.

Recommended for hot tubs is only 150 to 250 ppm, which is still relatively hard, but somewhat softer.
If water is too hard, it can be run through a water softener. If it is too soft, small amounts of minerals can be added.