Because the tank is vented to the atmosphere, contaminants may enter, causing bacterial growth that's controlled with ozone or chlorine. Otherwise, water can be sterilized with an ultraviolet sterilizer after it leaves the tank. Pressurization systems include a pump and a bladder tank to pressurize the house with water stored in atmospheric storage. Water pressure for the house can be adjusted to be greater than the pressure of the feed line into the house, or less. Post-treatment can incorporate many processes.
Carbon can also remove trace amounts of hydrogen sulfide gas in water.
Depending on the pH of the feed water, Reverse Osmosis can decrease the pH leaving it slightly acidic. Acidic water can corrode piping and fixtures. A calcium carbonate tank can be used to increase the pH. Gases, such as carbon dioxide and hydrogen sulfide, will pass through the Reverse Osmosis system. These can be removed by aeration.