Spring water was generally considered to be the healthiest and tastiest type of water. While philosophers like Hippocrates and Vitruvius thought water from hot springs was heavy and unclear, containing small particles of rock, water from cold springs was considered very healthy. The location of the spring was also a large factor. Vitruvius argued that mountain springs are superior to springs from flat land because the latter are exposed to more sunlight. Because he believed that the sun attracted the lightest water, leaving only heavy water behind, springs in flat areas that are exposed to more sunlight produce heavier water. He also claimed that northern springs are superior to springs from the other cardinal directions, though it is unclear why. Similarly, Hippocrates claimed that springs to the east are best, with northern springs coming in second. These were followed by western springs, with southern springs being the worst.

Hippocrates explained the concept of evaporation by saying that the sun attracts light water, but will leave heavy water behind. This is visibly evident if you leave a cup of salt water to evaporate—the water is gone, and the elements (in this case salt) are left behind. For this reason, he and other ancient philosophers considered rainwater to be very healthy, although not as tasty as spring water. They attributed the taste of water to certain minerals picked up when it flowed through earth from springs. Although too many minerals would make the water heavy, unclear, and unhealthy, limited minerals gave water its flavor. This is why some springs were more preferable than others. Rain water, being void of most elements, was lacking in taste, and as such was considered a good second option if cold spring water were not available.

Most ancient philosophers agreed that well water is a good alternative to spring water. Hippocrates valued water that remained cool in the summer and warm in the winter, relative to other kinds of water. Well water is deep enough that its temperature does not fluctuate as much as surface water or water stored in cisterns. However, this is really only true of water at the bottom of the well, as water at the surface is warmed by the sun and cooled by winter air temperatures. If you have ever swam in a lake, you may have noticed that the water around your feet felt colder than the water at the surface. Similarly, in winter it is only a few inches on the surface of the lake that actually freeze. Hippocrates observed these same phenomena in wells, and concluded that the deeper well water would be best for drinking. Other philosophers, such as Celsus, denounced well water as being the worst source of drinking water due to its static nature, and its accumulation of algae.

Surface water was generally considered to be the worst source of drinking water by ancient philosophers. Due to its stagnant nature, it is most likely to accumulate algae and host other living organisms. Hippocrates argued that surface water, often being the basin of a watershed, or the convergence of several different water sources, would be dominated by the strongest of those sources. Because the strongest tasting sources of water were full of elements, this meant that surface water was considered heavy and unclear. Vitruvius agreed with this sentiment, also arguing that rivers imbibe whatever soil they run through. Therefore, rivers flowing into a basin could be tainted, potentially with lethal effect. Galen, well known for his medical contributions to the ancient world, simply said not to drink water from pools, puddles, or marshes.

Wells are structures built to draw water from an underground source, specifically surface water. Wells are created when nearby springs are not available, because surface water is second to spring water due. They are often created near sanctuaries and on hilltops to honor deities. However, choosing the location requires proper research.

In Vitruvius, we learn about choosing the best location for a well. We are taught to dig where water vapor rises from the ground and where vegetation is found. Further tests, such as a bowl condensation test, was used to ensure that enough vapor rises from this area to indicate a body of water lies beneath

Additionally, the ground itself mattered. Vitruvius explains that caly and gravel provided water with a Poor taste, that pebbles create a better taste, and that black earth has the best taste.

Once a well is constructed, the Ktesibius pump was used to draw water up from the well. This pump was invented by Greek engineer Ktesibios and was strong enough to not only produce jets of water, but also help lift the water up from the wells.

Cisterns are waterproof reservoirs built to store water, usually rainwater. However, some also store water that's been transported using an aqueduct system. Most are built underground and can span vast areas of land.

The cistern is a paradox. Although rainwater is seen as the best water due to its purity, cistern water is the least desirable, because it is even more stale than surface water. This is because the walls of a cistern can become covered in mold, and bacteria is given the chance to grow in such conditions. However, many cisterns had sand purification to filter the wate rbeing stored.

Most philosophers such as Aristotle advise that cistern water should only be consumed as a last resort due to its staleness. In many civilizations, the cistern is used as a backup water supply when no other source is available.

The roman aqueducts consists of a series of channels that hesavily relied on gravity to transport from away location into the city. They heavily drew from spring water sources, but also drew from alternative sources for-non-consumption purposes. If there were hills between the city and the source, subterranean channels would be dug.

Once the water passes through the filtration (discussed later) system and reaches the city, it is stored in a central reservoir (cistern). Then it is diverged to three destinations: Basins and fountains, baths, private houses.

The best water was used for consumption, while surface water may have been used for bathing.

Susceptible to mold, these aqueducts required consistent upkeep and ventillation.

Infrastructure designed to contain and transport water required intensive upkeep.

Due to the staleness of cistern water and the presence of mold, aqueducts, cisterns, and wells required intense upkeep. To account for this, these structures were designed so that the mold contamination level could be not only monitored, but also cleaned. Line-inspectors were able to enter the structure through channels and ducts. Some of these shafts were also vertical, serving as vents for the reservoir. This vertical ventillation was also meant to air out the space and prevent mold build-up. The task of cleaning the structure's walls itself was often delegated to the slaves, because it required large scale labor.

Egyptians are known to have used the principle of coagulation sometime around 1500 BC. They did this by adding a chemical alum to the impure water. The alum then bonded with any suspended particles and sinks them to the bottom of the container. This water is then further boiled, filtered, and consumed as needed. (coagulation)

Egyptians were also known to use natural herbs, such as Amla and Vetiver to purify their water. Similar to the mayans, they also used stones such as quartz crystals, garnet and pearls for water as well. (coagulation)